and air, and support plants (anchorage). Soil is derived out of ..... Use alternative energy sources (e.g. energy saving stoves, biogas, saw dust, ...... During March to September when the sun is in the northern hemisphere the shade ...... In some parts of the country land holding has become as small as 0.25 acres supporting a.
FOREWORD Majority of people in East Africa depend on land based resources. However, recent studies indicate that there is extensive land degradation in the region,caused in part by unsustainable land use practices such as deforestation, poor farming methods leading to soil erosion, soil fertility decline, and loss of biodiversity. Land degradation has in turn led to reduced crop and animal productivity. This is an unfortunate situation considering Uganda’s growing population. Further more,land degradation contributes immensely to pollution of water bodies in the region, through eutrophication (extensive enrichment of the lake with nutrient enriched sediments from the land through soil erosion).This causes extensive growth of water weeds, pollution of water bodies, and inturn reduces fish catches, increases water treatment costs and increases the incidence and occurrence of water-borne diseases. The Lake Victoria Environmental Management Project Phase Two (LVEMP II) was conceived to among others, reduce land degradation. This was achieved through the Watershed Management Component of the project that supported districts and communities to implement sustainable land and environmental management sub projects geared towards reducing land degradation in selected hot spots within the lake basin. In Uganda, the targeted area was Katonga sub catchment. The interventions covered a range of activities such as: control of soil erosion, soil fertility management, increasing tree cover, use of energy saving cooking stoves, as well as supporting communities undertake alternative livelihood interventions such as livestock husbandry and apiary, to reduce pressure on the land and the lake resources. These activities were technically backstopped by NARL in collaboration with NaFORRI, MAAIF, NALIRRI, plus the district and private sector representatives. In an effort to promote sustainable landuse and environmental management in the region, a training manual has been prepared to guide field trainers and farmers on various topics drawing on experience and lessons learned during implementation of LVEMP II. This manual is divided in two volumes: volume one covers: soil and water management, forestry (tree nursery management, afforestation, agro-forestry), energy saving technologies, and records keeping. Volume two covers: improved livestock (dairy, poultry, piggery, goat and apiary), plus pasture establishment and management. The manual is intended to equip trainers and users with appropriate knowledge and skills for better production of different enterprises, and increase incomes while conserving the environment. We do hope that trainers will find this manual useful and put them to the right use, to promote sustainable land and environmental management in the region.
Dr. Ambrose Agona DIRECTOR GENERAL NARO
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ACKNOWLEDGEMENT Preparation of this training manual has been undertaken by technical officers from different institutions who have been backstopping communities during the implementation of LVEMP II activities. The institutions include: Ministry of Water and Environment (MWE),the Lake Environmental Management Project (LVEMP) secretariat, Ministry of Agriculture, Animal Industry & Fisheries (MAAIF), National Agricultural Research Organization (NARO), and specifically National Agricultural Research Laboratories (NARL), National Forestry Resources Research Institute (NaFORRI) and the National Livestock Resources Research Institute (NaLIRRI). We are grateful to the technical team for their devotion to this work and for the support that the administration of the various institutions has offered to the team during implementation of LVEMP II project activities. We thank LVEMP II project under the Ministry of Water and Environment (MWE) and the World Bank for the financial support which facilitated the team to prepare this training manual. We thank the LVEMP coordinators, CAOs, technical officers and administration from the districts of Gomba, Kalangala, Kalungu, Masaka, Mityana, Mpigi, Mubende, Namayingo and Rakai for their immense contribution to LVEMP II activities. The district LVEMP coordinators and technical officers also reviewed the manual and made valuable input. We thank the Advisory committee for their continuous guidance during preparation of the manual. The Technical editorial team ensured quality of the material presented. Farmers, trainers and all the LVEMP beneficiaries from the nine districts shared their experiences during preparation of this manual. These experiences (especially the questions raised during the different training sessions) inspired the backstopping team to document them into a training manual that will benefit SLM practitioners for a longer time beyond the lifespan of the project. We thank you all.
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LIST OF CONTRIBUTORS Authors
Dr.OnesimusSemalulu, Principal Research Officer, NARL, NARO …..……….....Team leader Dr. James Higenyi, Senior Veterinary Inspector, MAAIF ……………..….……..……Member Mr. Charles Rusoke, former Senior Land Management Specialist, MAAIF …….……Member Ms. Diana Namayanja, Apiculturalist, NaLIRRI, NARO …………..…….…….……..Member Ms. Grace Abigaba, Research Officer, NaFORRI, NARO ……………..……...………Member Mr. Stephen Kayiwa, Senior Laboratory Technician, NaLIRRI, NARO ….…..………Member Ms. Grace Rwabaingi, former Research Officer, NaFORRI, NARO ……...…….…….Member Mr. Patrick Makhosi, Research Assistant, NARL, NARO ……………..…….……….Member Mr. George Niyibizi, Senior Technician, NaFORRI, NARO ……………..….….…….Member Dr.AnnuciateNakiganda, Senior Research Officer, NaLIRRI, NARO ………......…….Member
Advisory Committee
Prof. Wilberforce Tushemereirwe………………………………...……………Director, NARL Ms. Florence Grace Adongo ……..…….….…Director, Water Resources Management, MWE Mr.Sowed Ssewagudde……………….....……National Project Coordinator LVEMP II, MWE Dr.Evelyn Komutunga…………………………...……...…….Head, Soils , Programme NARL
Technical Edit
Dr. Drake Mubiru………………………………...…………Principal Research Officer NARL Dr. Crammer K.Kaizzi………………………………….....…... Senior Research Officer NARL Mr. Stewart Kyebogola…………………………………..……….……….Makerere University
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TABLE OF CONTENTS LIST OF CONTRIBUTORS.......................................................................................................i FOREWORD.............................................................................................................................ii TABLE OF CONTENTS..........................................................................................................iii LIST OF TABLES...................................................................................................................viii LIST OF FIGURES...................................................................................................................ix LIST OF BOXES......................................................................................................................xi LIST OF ACRONYMS............................................................................................................xii ACKNOWLEDGEMENT.......................................................................................................xiii GENERAL INTRODUCTION...............................................................................................xiv GENERAL GUIDELINES FOR TRAINERS/ FACILITATORS............................................xv MODULE 1................................................................................................................................2 SOIL AND WATER MANAGEMENT.......................................................................................3 CHAPTER ONE: INTRODUCTION TO SOIL AND WATER MANAGEMENT....................3 1.1 Background to Soil and Water Conservation (SWC). ....................................................3 1.2 Importance of soil and water management to crop production.......................................3 1.3 Managing soil physical, chemical and biological properties:.........................................3 1.4 Soil organic matter management:....................................................................................4 1.5 Soil..................................................................................................................................4 1.6 Choice of soil and water management measures.............................................................4 1.7 Challenges of soil and water management.....................................................................4 CHAPTER TWO: KNOWING YOUR SOIL.............................................................................5 2.1 Key definitions...............................................................................................................5 CHAPTER THREE: SOIL FERTILITY CONCEPT AND MANAGEMENT...........................8 3.1 Introduction.....................................................................................................................8 3.2 Essential plant elements..................................................................................................8 3.3 Nutrient losses...............................................................................................................10 3.4 Soil fertility and nutrient management..........................................................................10 3.4.1 Soil nitrogen..................................................................................................................10 3.4.2 Soil phosphorus..............................................................................................................12 3.4.3. Soil potassium, calcium and magnesium......................................................................12 3.4.4 Micro-nutrients..............................................................................................................12 CHAPTER FOUR: SOIL FERTILITY LOSS AND POSSIBLE COPING METHODS.........13 4.1 Soil fertility loss............................................................................................................13 4.2 Soil erosion....................................................................................................................13 4.2.1 Types, causes and coping methods for water-induced soil erosion...............................13 4.2.2 Effects of soil erosion....................................................................................................19 4.3 Crop cultivation.............................................................................................................19 4.4 De-vegetation................................................................................................................19
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CHAPTER FIVE: SOIL AND WATER CONSERVATION STRUCTURES..........................21 5.1 Relationship between precipitation, infiltration and runoff..........................................21 5.2 Effect of soil management practices on runoff and soil erosion...................................21 5.3 Types of soil conservation structures............................................................................22 5.4 Types of water conservation structures.........................................................................22 CHAPTER SIX: SOIL AND WATER CONSERVATION EQUIPMENT AND STRUCTURES.........................................................................................................................26 6.1 Types of field survey equipment...................................................................................26 6.2 Line level......................................................................................................................26 6.3 The A-frame..................................................................................................................33 CHAPTER SEVEN: AGRONOMIC/CULTURAL CONSERVATION FARMING MEASURES.............................................................................................................................33 7.1 Introduction...................................................................................................................33 7.2 Conservation farming practices....................................................................................33 CHAPTER EIGHT: INTEGRATING SOIL CONSERVATION WITH FARMING SYSTEMS.................................................................................................................................38 8.1 Introduction...................................................................................................................38 8.2 Hillside farming and conservation farming systems.....................................................38 8.2.1 Agro-forestry.................................................................................................................38 The main purposes of Agro-forestry are;......................................................................38 8.3 Pasture management on slopes......................................................................................38 References......................................................................................................................40 MODULE 2..............................................................................................................................41 FORESTRY................................................................................................................................42 CHAPTER ONE: FORESTS AND WOODLANDS................................................................43 1.1 Introduction...................................................................................................................43 1.2 The following activities have contributed to the environmental degradation...............43 CHAPTER TWO: TREE NURSERY ESTABLISHMENT AND MANAGEMENT...............44 2.1 Introduction...................................................................................................................44 2.2 What is a tree nursery? .................................................................................................44 2.2.1 Types of tree nurseries...................................................................................................44 2.2.2 Tree nursery terminologies...........................................................................................45 2.3 Nursery establishment...................................................................................................45 2.3.1 Nursery planning..........................................................................................................45 2.3.2 Factors to be considered in selecting the site for a nursery..........................................45 2.3.3 Basic tree nursery facilities...........................................................................................46 2.4 Nursery site preparation and layout..............................................................................47 2.4.1 Materials and equipment needed for Nursery establishment include:..........................47 2.4.2 Nursery site preparation................................................................................................47 2.4.3 Nursery layout...............................................................................................................47 2.5 Standard nursery operations and management..............................................................48 2.6 Sowing seed..................................................................................................................49 2.7 Watering........................................................................................................................50 v
2.8 Pricking out...................................................................................................................50 2.9 Shade.............................................................................................................................51 2.10 Weeding.........................................................................................................................51 2.11 Root pruning.................................................................................................................51 2.12 Hardening off................................................................................................................52 2.13 Sorting, Culling and grading.........................................................................................52 2.14 Seedling protection/control...........................................................................................52 2.15 Nursery records.............................................................................................................54 2.16 Nursery calendar............................................................................................................54 2.17 Vegetative propagation..................................................................................................55 2.18 Grafting.........................................................................................................................56 2.19 Budding.........................................................................................................................56 2.20 Cuttings.........................................................................................................................57 2.21 Layering........................................................................................................................57 2.22 Plant tissue culture........................................................................................................59 2.23 Wildings........................................................................................................................59 2.24 Pests and diseases of fruit trees;....................................................................................60 2.25 Sourcing tree seed /treatment. ......................................................................................60 2.26 Methods of seed collection...........................................................................................60 2.27 Seed extraction..............................................................................................................61 2.28 Tree nursery as a business.............................................................................................62 2.28.1 Evaluation of a nursery enterprise (SWOT analysis)....................................................62 2.28.2 Nursery budgeting.........................................................................................................62 2.29 Liquid manure production............................................................................................65 CHAPTER THREE: PLANTATION AND WOODLOT ESTABLISHMENT........................67 3.1 Introduction...................................................................................................................67 3.2 Surveying and mapping.................................................................................................67 3.3 Choice of species for planting depends on:..................................................................67 3.4 Lining out (laying out planting positions).....................................................................68 3.5 Pitting and Planting.......................................................................................................69 3.6 Silvi-cultural methods:..................................................................................................70 3.6.1 Weeding:......................................................................................................................70 3.6.2 Pruning:.........................................................................................................................71 3.6.3 Coppicing.......................................................................................................................72 3.6.4 Thinning:.......................................................................................................................72 3.7 Protection of trees..........................................................................................................73 3.8 Harvesting operations...................................................................................................78 3.9 Tree growing as business.............................................................................................79 CHAPTER FOUR: AGROFORESTRY PRACTICES.............................................................82 4.1 What is Agroforestry?...................................................................................................82 4.2 What can Agroforestry Provide?...................................................................................82 4.3 Why Agroforestry practices?.........................................................................................82 4.4 Types of agroforestry practices.....................................................................................83 4.5 Common management practices for farm trees............................................................87 References.....................................................................................................................91 vi
MODULE 3..............................................................................................................................92 ENERGY SAVING TECHNOLOGIES...................................................................................93 CHAPTER ONE: ENERGY SAVING TECHNOLOGIES......................................................94 1.1 Introduction...................................................................................................................94 CHAPTER TWO: ENERGY COOK STOVES........................................................................95 2.1 Introduction...................................................................................................................95 2.2 Environmental Conservation through Use of Energy saving Cooking Stoves:..........100 2.3 Solar ovens/cookers....................................................................................................100 CHAPTER THREE: BIOMASS BRIQUETTE PRODUCTION...........................................102 3.1 Introduction.................................................................................................................102 3.2 Types of briquettes......................................................................................................102 3.3 Requirements for briquette production........................................................................103 3.4 Preparation of Feedstock.............................................................................................104 3.5 Carbonization of biomass............................................................................................104 3.6 Preparation of feed stock.............................................................................................104 3.7 Binding and Binder preparation and mixing................................................................106 3.8 Briquetting..................................................................................................................106 3.9 How briquettes are produced......................................................................................106 3.10 Drying, Packing and marketing..................................................................................106 3.11 Beneficiaries................................................................................................................107 3.12 Advantages of briquetting...........................................................................................107 3.13 A Commercial Case for Briquette Businesses............................................................107 CHAPTER FOUR: BIO-GAS PRODUCTION, USE AND MANAGEMENT.....................109 4.1 Introduction.................................................................................................................109 4.2 Importance of bio-slurry..............................................................................................109 4.3 The Biogas Plant..........................................................................................................111 4.4 General Operation and Maintenance...........................................................................112 4.5 Key factors which will favour gas production............................................................114 4.6 Mixing Chamber Maintenance....................................................................................115 4.7 Expansion Chamber Maintenance...............................................................................115 4.8 Slurry Pit and Compost Pit Maintenance....................................................................115 4.9 Water Trap Valve Maintenance...................................................................................115 4.10 Pressure gauges...........................................................................................................116 4.11 Pipe maintenance........................................................................................................116 4.12 Challenges of the biogas technology...........................................................................116 4.13 Frequently asked questions.........................................................................................118 4.14 Conclusion...................................................................................................................119 References....................................................................................................................120 MODULE 4............................................................................................................................121 FARM RECORDS..................................................................................................................122 CHAPTER ONE: The Importance of Keeping Farm Records...............................................123 1.1 Introduction.................................................................................................................123 1.2 what records need to be kept on the farm?..................................................................123 1.3 Other advantages of keeping farm records:................................................................127 vii
1.4
Challenges of keeping farm records............................................................................127 Conclusion....................................................................................................................128 References....................................................................................................................129
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LIST OF TABLES Table 1.2. 1. Characteristics of different soil types………………………………….............…7 Table 1.3. 1. Nutrient losses and possible management practices …….....................................11 Table 2.2. 1. Tree nursery diseases and pests, symptoms and control measures…...................53 Table 2.2. 2. Nursery calendar...................................................................................................55 Table 2.2. 3. SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis.................63 Table 2.2. 4. Budgeting for nursery business............................................................................64 Table 2.3. 1. Pruning schedule..................................................................................................72 Table 2.3. 2. Thinning Schedules for Eucalyptus and Pinus tree species..................................73 Table 2.3. 3. Key pests and diseases of trees found in Uganda.................................................75 Table 2.3. 4. Breakdown of costs and returns in tree growing..................................................80 Table 2.3. 5. Tree species which are drought resistant..............................................................81 Table 2.4. 1. Tree species and shrubs that improve soil fertility...............................................89 Table 3.3. 1. Comparison of price per kg of different wood-based energy sources................108 Table 3.4. 1. Various sizes of bio-gas plants...........................................................................112 Table 3.4. 2. Potential problems and likely solutions in a biogas digester/plant....................117
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LIST OF FIGURES Figure 1.3. 1: Visual symptoms of nutrient deficiencies and disorders......................................9 Figure 1.4. 1: Sheet erosion in Namayingo district, Uganda....................................................14 Figure 1.4. 2: Sheet erosion in Namayingo district, Uganda....................................................14 Figure 1.4. 3: Small rills............................................................................................................15 Figure 1.4. 4: Deep rills............................................................................................................15 Figure 1.4. 5: Gully in Mubende District, Uganda...................................................................16 Figure 1.4. 6: Gully in Mubende District, Uganda...................................................................16 Figure 1.4. 7: Armour layer, Rakai district...............................................................................17 Figure 1.4. 8: Rills on bare slope soil, Rakai............................................................................17 Figure 1.4. 9: A gully in a banana field, Mpigi.........................................................................17 Figure 1.4. 10: Banana roots exposed by erosion, Mpigi.........................................................17 Figure 1.4. 11: Rocks exposed by erosion, Rakai district.........................................................18 Figure 1.4. 12: Change in soil colour after using mucuna green manure, Mpigi district.........18 Figure 1.4. 13: Exposed borehole foundation in Mityana........................................................18 Figure 1.5. 1: Roadside runoff water pits..................................................................................22 Figure 1.5. 2: V-shaped bunds (Negarims)...............................................................................23 Figure 1.5. 3: Semi-circular bunds (micro-catchments)...........................................................23 Figure 1.5. 4: Trapezoidal bunds...............................................................................................24 Figure 1.5. 5: Planting pit (water pocket).................................................................................24 Figure 1.5. 6: Micro - basin.......................................................................................................24 Figure 1.5. 7: Sunken beds........................................................................................................25 Figure 1.5. 8: Roof water harvesting.........................................................................................25 Figure 1.5. 9: Compound runoff water harvesting....................................................................25 Figure 1.6. 1: components of a line level..................................................................................26 Figure 1.6. 2: Graduation boa...................................................................................................26 Figure 1.6. 3: Setting up a line level.........................................................................................27 Figure 1.6. 4: Using the line level to determine the vertical interval........................................29 Figure 1.6. 5: Location of contours for conservation structures...............................................30 Figure 1.6. 6: Construction of a cut-off drain (Fanya chini)....................................................31 Figure 1.6. 7: Construction of ‘Fannya-Juu’ bund....................................................................31 Figure: 1.7. 1: Multiple cropping..............................................................................................35 Figure: 1.7. 2: Stone bunds.......................................................................................................35 Figure: 1.7. 3: Mulching in a banana field................................................................................35 Figure: 1.7. 4: Sketch of mulching in banana field...................................................................35 Figure: 1.7. 5: Mucuna used as cover crop...............................................................................35 Figure: 1.7. 6: Raised bed.........................................................................................................35 Figure: 1.7. 7: A sketch of compost making.............................................................................37 Figure 1.8. 1: Example of Agro-forestry practice.....................................................................38 Figure 1.8. 2: A farmer feeding cattle under zero grazing.........................................................39 Figure 2.2. 1: Photo of a tree nursery........................................................................................44 Figure 2.2. 2: Nursery layout....................................................................................................47 Figure 2.2. 3: Example of good pot filling................................................................................49 Figure 2.2. 4: a and b. Root pruning using a knife and pruning saw........................................52 Figure 2.2. 5: Top cleft grafting................................................................................................56 Figure 2.2. 6: Simple layer with stake holding shoot in place..................................................58 Figure 2.2. 7: Compound (serpentine) layering........................................................................58 x
Figure 2.2. 8: Sequence of air layering; Girdling, and tying off...............................................59 Figure 2.2.9. Preparation of Liquid manure..............................................................................66 Figure 2.3.1. Lining out and pitting..........................................................................................68 Figure 2.3.2: Planting procedure...............................................................................................70 Figure 2.4. 1: Scattered trees on farmland.................................................................................83 Figure 2.4. 2: Grevillea robusta trees planted along the boundary...........................................85 Figure 2.4. 3: Improved mango variety and Improved Avocado Variety..................................85 Figure 2.4. 4: A well-managed woodlot of Eucalyptus trees....................................................86 Figure 2.4. 5: Calliandra fodder bank. Interplant of Napier grass with Calliandra...................87 Figure 2.4. 6: Different types of crops; trees for fruits, firewood, fodder medicine.................87 Figure 3.3. 1: Different forms of briquettes:...........................................................................102 Figure 3.3. 2: Non-carbonised straw briquette (piston extruded)...........................................102 Figure 3.3. 3: Two types of biomass carbonisation kilns........................................................104 Figure 3.3. 4: From left-right: Grinding large charcoal fines into dust for briquetting;.........105 Figure 3.3. 5: Binder preparations and mixing.......................................................................105 Figure 3.3. 6: Briquetting machine and briquettes..................................................................106 Figure 3.3. 7: Locally made solar dryers.................................................................................106 Figure 3.3. 8: Average market prices of charcoal in Kampala, (Source: UBOS)....................107 Figure 3.4. 1: Biogas plant at Mr & Mrs. Bamulumbye Remegio’s home,...........................111 Figure 3.4.2: A Biogas Pressure Gauge...................................................................................113 Figure 3.4. 3: Biogas stove......................................................................................................114 Figure 3.4. 4: Biogas lamp......................................................................................................114 Figure 3.4. 5: Picture of water trap valve................................................................................115 Figure 3.4. 6: Picture of gas pipe............................................................................................116
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LIST OF BOXES Box 1: determining of soil texture in the field............................................................................5 Box 2: Selected visual indicators of soil erosion......................................................................20 Box 3: Possible coping methods for devegetation....................................................................21 Box 4: Example of crop rotation sequence...............................................................................37
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LIST OF ACRONYMS DDSA
:
Diagnostic Decision Support Aid
FAO
:
Food and Agriculture Organization
MAAIF
:
Ministry of Agriculture, Animal Industry and Fisheries
MWE
:
Ministry of Water and Environment
NaFORRI
:
National Forestry Resources Research Institute
NAGRC&DB :
National Animal Genetic Resource Centre and Data Bank
NaLIRRI
:
National Livestock Resources Research Institute
NARL
:
National Agricultural Research Laboratories
NARO
:
National Agricultural Research Organization
RELMA
:
Regional Land Management Project
SLM
:
Sustainable Land Management
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GENERAL INTRODUCTION Training objectives Equip users (extension officers, community or farmers) with appropriate knowledge and skills for better production of different enterprises • Enhance the ability of users to increase income through improved production while conserving the environment Key Learning outcomes: • Farmers should be able to site, design and construct good nurseries and livestock shelters • Farmers should be able to identify and select better varieties/ breeds and propagation/ breeding options • Farmers should be able to identify, prevent, and control pests and diseases for the different enterprises • Farmers should be able to carry out routine management practices in order to increase on profitability of the target enterprise • Farmers should be able to properly manage the different enterprises
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GENERAL GUIDELINES FOR TRAINERS/ FACILITATORS Facilitation is not teaching or lecturing, rather it is guiding and motivating the learner to enthusiastically acquire, retain and use the needed knowledge, skills, habits/ behaviour and attitudes in a simple, easy and smooth manner. The learning may involve acquisition, modification or adjustment of existing knowledge, skills, behaviour and attitudes to cope with new circumstances. Thus, effective facilitation of adult learning requires the trainer/ facilitator to use different skills and participatory methods that will interest, motivate and re-enforce learning. The facilitator must also enable the learner to retain what she/he has learnt and to transform it into action. Thus the facilitator must be skilful. Guidelines 1. Prepare study and get familiar with the culture, traditions, values and socio- economic relationships of the community so that you adjust yourself accordingly in terms of style, clothing and language, and avoid issues that may conflict with norms. 2. It is important to always apply the adult facilitation skills: • Inquiry - Probe/ask and encourage questions • Interaction - Use participatory methods such as: group work, discussions, case studies, role plays, story-telling, sharing proverbs, experience sharing, question and answer demonstrations, brain storming, visualization in participatory activities / exercises/ observations. 3. Expose the learner to different ways of learning (seeing, doing, and thinking, feeling, hearing, smelling and tasting). 4. Ensure an informal and favourable learning environment. 5. Make Pre-training preparations by securing all necessary training materials, checking on the training venue and preparing the schedule for the training. 6. Warmly welcome the learners • Presentation - Make the presentation lively and be cheerful throughout the session • Communication - Use a combination of oral, written and body language. Listen carefully to understand the audience and give feedback. 7. Set the learning climate by creating a warm and friendly environment at the beginning of each session so that the participants are able to talk and express their views freely. 8. At the start of each session introduce the training, brief the learners about the title of the topic/session and the learning objectives. 9. Ask learners to give their experiences about the new topic. • Focus on the important aspects or key areas of the topic/session at hand. Avoid giving irrelevant information. • At the end of each session make a conclusion and where applicable introduce the next topic/session and ask learners to think about it. • Where applicable, review what was learnt in the previous topic/session before starting a new one. Give a chance to each participant to contribute. Compliment their answers by emphasizing the key points of the previous topic. If you get unsatisfactory answers, review your teaching methods and incorporate those that can improve their learning.
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• Reinforce learning by; – Using language most understood – Simplifying the content and reconsidering the sequence or pattern of it – Changing the facilitation skills, instructional methods/techniques or combine techniques – Giving practical and where possible live examples – Conducting method and result demonstrations – Encouraging hands-on activities or learner to review what she/he has learnt – Giving exercises – Encouraging questions and free interactions – Encouraging the learner to associate the new information/skill/ behaviour with some thing she/he already knows – Relating the subject/topic to something beneficial or critical – Giving an example (story) from experience or refer to something currently topical (up to date/modern) and relevant – Generating summary – Jointly make an agreed implementation and follow-up plans – If possible plan for exposure excursions and study tours The Trainer is advised to always consult a local extension officer or Agricultural service provider.
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VOLUME ONE
1
MODULE 1 SOIL AND WATER MANAGEMENT
Onesmus Semalulu (NARL) Patrick Makhosi (NARL) Charles Rusoke (Private Sector)
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CHAPTER ONE: INTRODUCTION TO SOIL AND WATER MANAGEMENT 1.1 Background to Soil and Water Conservation (SWC) In East Africa, majority of the population particularly in rural areas, derive their livelihoods from agriculture. Indeed the economies of most developing nations largely hinge on agriculture. However, many farmers rarely get close to the expected crop variety potential yields. Many factors are responsible for the yield gap including pests, diseases, weatherrelated problems and, soil-related factors. Among the soil-related factors include: i. Inadequate use of appropriate soil management practices, leading to extensive soil erosion, nutrient mining and declining soil fertility ii. Limited soil moisture conservation which affects crop growth and development. It is therefore imperative that farmers integrate SWC practices into farming. Integration of SWC into farming hinges largely on farmers’ knowledge and ability to invest into the practices. To encourage and guide farmers to adopt and sustain SWC practices, the agricultural service providers need to be equipped with a wealth of knowledge and skills. 1.2 Importance of soil and water management to crop production Soil is a medium for plant growth. It stores nutrients required for proper plant growth. Soil also offers a medium where plant roots anchor and be able to trap sunshine and carbon dioxide from the atmosphere, required for grow. Plants take up nutrients from the soil in solution form. The nutrients taken up are utilized with carbon dioxide in presence of water and sunshine to manufacture food both for man and the plant’s own use. For tropical soils most nutrients required by plants are derived from soil organic matter which is usually black and found in the top part of the soil, which varies from about 10 to 30cm thick.
Crop nutrients are associated with soil organic matter found mainly in the surface layer of the soil, they are susceptible to losses through erosion by water and wind, once vegetation cover is removed. The nutrients are also prone to leaching in high rainfall areas. When these nutrient losses are coupled with deterioration of soil physical properties, crop yields gradually fall especially where intensive cropping is practiced.
Sustainable soil productivity implies that a soil resource can give the desired crop-animal yield and maintain it for a long time for the benefit of the present and future generations. To achieve this, proper management of the soil and the land in general, is essential. Proper soil and water management is a component of Integrated Soil Fertility Management (ISFM) which entails a number of inter-related practices. Briefly, they include soil erosion prevention and control; water conservation/management; managing soil physical, chemical and biological properties; organic matter management; soil fertility management and nutrient recycling.
1.3 Managing soil physical, chemical and biological properties: Soil physical characteristics (e.g. structure, texture, porosity, permeability) affect soil water relations (percolation, infiltration, and availability), aeration and root development, among other things. Soil physical properties are normally managed through proper tillage practices and organic matter management. Soil also serves as a habitat for many living organisms (macro and micro). These perform essential functions such as improving soil aeration and 3
permeability (hence better root development), decomposition of plant residues, recycling of plant nutrients, etc.
Proper organic matter management promotes soil biological life leading to a better soil medium. Soil chemical properties reflect its ability to supply plant nutrients, among other things.
1.4 Soil organic matter management: Organic matter is an important component of the soil medium in improving soil physical and biological properties. It is a major source of nutrients in Uganda soils. Organic matter also serves as a nutrient reserve; many nutrients are replenished through organic matter decomposition. Organic matter management implies recycling of crop residues, mulching, use of compost, farmyard manure, animal manure, green manures, etc. It also implies prevention of soil erosion since organic matter is mainly found in the topsoil. Fallow and minimum tillage practices reduce organic matter depletion and are therefore good components of organic matter management. 1.5 Soil fertility management and nutrient recycling/replenishment: Soil nutrients are lost as a component/constituent of crop harvesting, and also through erosion and leaching. To maintain soil fertility, the nutrients lost must be replaced. This can be achieved through addition of external inputs e.g. fertilizers (organic and inorganic), biological nitrogen fixation (BNF), recycling plant and animal residues, among others. Sound crop management e.g. crop rotation and fallow (natural or improved) also helps to reduce soil fertility decline and improve soil fertility. Crop rotations involving shallow and deep rooted crops help to recycle nutrients back into the root zone. While nutrients are removed from the entire farm (through crop harvesting), farmers often tend to recycle residues around the homestead, leaving other areas of the farm impoverished of nutrients thus creating a soil fertility gradient on the farm. Farmers need to replace/recycle nutrients in the entire field. 1.6 Choice of soil and water management measures/practices The choice of soil and water conservation/ management measure to use depend on characteristics of the land (e.g. slope), resources available to the farmer (i.e. affordability in terms of labour and capital). Among other things, aspects like government policies (e.g. land tenure) also affect the level of investment and type of soil conservation measure a farmer is likely to put in place. Soil erosion control also involves using appropriate land preparation and crop management practices e.g. cultivating and planting along the contour (across the slope), not up and down the slope. 1.7 Challenges of soil and water management Soil and Water Conservation/Management is a key component of sustainable crop production. However, many practices are labour intensive, expensive and take long to yield results. As a result many farmers are reluctant to invest into soil and water conservation practices. In addition where a farmer does not have security of tenure over the land, s/he may not be motivated to invest in soil and water conservation. Nevertheless, for sustainable crop production, soil and water conservation needs to be implemented as part of good soil and crop husbandry practices. 4
CHAPTER TWO: KNOWING YOUR SOIL 2.1 Key definitions Soil is a medium for plant growth. It provides space for rooting, supplies nutrients, water and air, and support plants (anchorage). Soil is derived out of weathering rocks and decomposing organic materials. Soil contains rock mineral particles, air, moisture, living organisms and dead/decaying organic matter. The mineral part of a soil is made of sand, silt and clay.
a. Soil texture refers to the relative percentages of sand, silt and clay. Owing to the different proportions of sand, silt and clay, soils can differ in textures. Soil texture can be determined in the field or laboratory. A simple method for determining soil texture in the field is presented in Box 1.2.1. Box 1. Determining soil texture in the field Take a small handful of soil from the field, drip water slowly onto the sample until it reaches the “sticky point”, the point at which the soil adheres to itself but not to the hand. Using the moist soil sample form different shapes as shown below. The shape you can make roughly indicates the texture of soil. 1
2
Sand Soil remains loose and single grained and can only be heaped into a pyramid 3
Loamy Sand
Soil can be shaped into a ball 4
Silt loam
Loam Soil can be rolled into a cylinder, about 15 cm long
Soil can only be rolled into a short cylinder, about 5 cm long 5
6
Clay loam Soil can be bent into a U shape
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Light clay
Clay
Soil can be bent into a circle with cracks
Soil can be bent into a circle without cracks
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b. Soil structure: refers to the physical arrangement of soil particles. Soil particles can be unattached as in sandy soils or they can be closely packed together as in clay soils. Usually the particles are held together in aggregates (crumbs) with the formation of stable aggregates, an important feature of a productive soil. Higher organic matter content improves stability of soil aggregates. Soils with good structure allow seedlings to emerge easily and provide a ready supply of water and air to plant roots.
c. Organic matter: refers to the remains of living plants and animals after death and decomposition. It decomposes to form dark small particles called humus, which normally imparts a dark colour to soil. Humus contributes to soil structure and water holding capacity. Humus also acts as a source of food to important soil micro-organisms. During decomposition of organic materials, nutrients are released which serve as food for plants.
Organic matter contributes to soil fertility in the following ways: • Provides nutrients during decomposition • Increases the soil’s capacity to hold nutrients • Builds soil structure which increases water infiltration and water use by the crop • Protects the soil against rapid changes in acidity or alkalinity (soil pH). • Stores water and holds nutrients in soil
Soil organic matter content: The amount of organic matter in a soil depends on; i. Soil type – sandy soils usually have low organic matter than clayey ones ii. Temperature – influences the rate at which organic materials are decomposed by soil organisms. iii. Amount and type of organic material added as manure or as crop residues iv. Management practices – method and frequency of tillage - tilling soil increases organic matter breakdown – burning destroys organic materials in the soil (e.g. living and dead organisms), Soil organic matter can be increased through reduced tillage, planting cover crops, fallowing, addition of crop and animal residues, composts, farm yard manure, mulching, etc.
d. Soil fertility: refers to the ability of a soil to supply nutrients in the form and quantity required by a plant. Most tropical soils derive their fertility from organic matter.
e. Soil productivity: Is the ability of a soil to provide a favourable rooting medium for plant growth [ability to supply nutrients and provide a good physical environment for the roots (good aeration, structure, rooting depth, favourable temperature)].
f. Soil rooting depth: is an important indicator of soil’s ability to support crop growth by providing moisture, nutrients, and physical support. Soil rooting depth depends on the presence of rocks, layers in soil or cultivation pans, which restrict downward root penetration. 6
Shallow soils are poor for crops because of lower nutrient and water availability (smaller root volume) for plant growth. Soil erosion is one of the main causes of reduced rooting depth. Characteristics of soils of different textures Table 1.2. 1. Characteristics of different soil types Sand Clay – Large soil particles – Tiny soil particles (2 mm diameter or – Fine texture greater) – Very small air spaces – Coarse texture – Low aeration – Large air spaces – Low infiltration rate – High aeration – High water storage capacity – High infiltration rate – less runoff – Difficult to plough – Low water storage capacity – High nutrient retention – Easy to plough – Low nutrient retention Loam The characteristics for loam soil are intermediate between those of sand and clay soils.
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CHAPTER THREE: SOIL FERTILITY CONCEPT, EXPERIENCES, PROBLEMS AND MANAGEMENT 3.1 Introduction Soil fertility refers to the capacity of soil to store and supply essential plant nutrients in the amount and form that a plant can take up easily. For this to be achieved, soil must have good physical, chemical and biological properties, commonly referred to as “good soil health”. Thus, a fertile soil must:
a. b. c. d. e. f.
Be deep enough to enable roots explore a sufficient soil volume without any obstructing layer. Contain sufficient organic matter. Have good structure (based on the distribution and aggregation of particles) to ensure proper aeration, hence growth and development of roots. Have a favourable soil pH (pH range 5.5 to 6.5 for most crops). Have a good supply of both available and reserve plant nutrients. Be able to store soluble nutrients e.g. from both organic and inorganic fertilizers, and from decomposing materials, plus weathering of minerals.
3.2 Essential plant elements An essential plant element is one which: a. A plant cannot complete its life cycle without it b. Cannot be substituted by any other element c. Is involved in plant nutrition, e.g. forms a structural constituent or an essential metabolite. There are 16 essential plant elements. They include: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, molybdenum, boron, zinc, copper, iron, manganese and chlorine. However, some are required in larger amounts (e.g. N, P and K) and are referred to as macro elements, while others are required in very small doses (e.g. boron, zinc, etc.) and are referred to as micro elements.
Carbon is taken up as CO2 from the air; hydrogen and oxygen are derived from water. Carbon, hydrogen and oxygen form the basic building blocks of all plants. They are involved in formation of all organic plant constituents: carbohydrates, proteins, nucleic acids, etc. Other elements are derived from the soil solution. Essential plant nutrients can also be supplied to soil through addition of fertilizers (organic or inorganic), or through decomposition of plant and animal residues. Nitrogen can also be derived from the atmosphere through Biological Nitrogen Fixation (BNF) by legumes and free living micro-organisms. Shortage or lack of essential elements in a plant results in improper signs/ appearance and growth of a plant known as deficiency symptoms. Excess of an essential element may lead to toxicity in the plant. A Decision Decision Support Aid (DDSA) chart for quick identification of plant disorders is given in Fig. 1.3.1.
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Figure 1.3. 1: Visual symptoms of nutrient deficiencies and disorders (Source: Fairhurt, 2012)
3.3 Nutrient losses Soil nutrient losses occur through crop harvesting, erosion, runoff, leaching, immobilization, fixation, de-nitrification and volatilization. Due to these losses, soil fertility declines and there is need to replenish the nutrients lost. Most soils in Uganda are old and their nutrient reserves are very poor. The most limiting nutrients in Uganda soils include nitrogen, phosphorus and especially for bananas and root crops, potassium. The best way to manage our soils is by managing organic matter (see chapter 1 of this module). 3.4 Soil fertility and nutrient management Soil fertility management involves knowledge of the nutrient transformations (changes, gains and losses) that essential plant nutrients undergo in nature. Nitrogen is the most limiting of all nutrients due to the many transformations it undergoes. 3.4.1 Soil nitrogen Nitrogen transformations Nitrogen fixation: Nitrogen occurs naturally in abundance in the atmosphere, although this form is not directly available to plants. Through BNF and lightening, a small proportion of the atmospheric nitrogen can be fixed into plants and consequently, ends up into the soil. Nitrogen can also be added to soil through addition of fertilizers (organic or inorganic) and through atmospheric fixation via lightening.
Ammonium fixation: Some soil colloids are able to fix N preventing its loss from the soil. This can slowly be released into the soil solution from where it is taken up by plant roots.
Mineralisation: This refers to the conversion of organic N into inorganic N forms (e.g. ammonium): Organic-NH2 NH4+ Nitrification: Refers to the conversion of NH4+ into nitrate NH4+O2 NO2- + 2H + Energy nitrosomonas 2NO2- + O2 nitrobacter2NO3- + Energy Nitrification leads to formation of nitrate form (NO3-), a more readily leached form of nitrogen. Nitrogen losses and management practices Table 1.3.1 presents various ways in which nitrogen is lost in nature and the different practices a farmer should carry out to control nitrogen losses and manage his crops better.
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Table 1.3. 1. Nutrient losses and possible management practices Nutrient Nitrogen
Losses
Possible management methods
Leaching: nitrate dissolves in water and is moved to lower soil depths where plant roots can no longer extract it from Crop harvesting: nitrogen is lost every time we harvest a crop or cut grass to feed animals Volatilisation nitrogen is lost as ammonia gas (NH3) when soil pH is above 7 or when soil is dry, or under direct sunshine Immobilization – some of the nitrogen applied to soil may be taken up by micro organisms. This makes it unavailable to plants. Denitrification – loss of N in gaseous forms such as NO, N2O or N2 especially under flooded soil conditions Soil erosion – loss of topsoil by moving water takes organic matter and plant nutrients contained therein.
-Use less easily leached ammonium fertilizers, e.g. DAP, and not nitrate fertilisers -Split-apply N fertilisers instead of a single application -Plant deep-rooted crops after shallow rooted ones. -Recycle all plant, crop and animal residues -Apply nitrogen fertilizer when soil is moist, and when the weather is not too hot -Allow field to rest for at least two weeks after ploughing -Control soil erosion -Use leguminous crop/plant species in the cropping cycle
Phosphorus
► Soil erosion ► Crop harvesting ► Fixation by soil constituents.
-Reduce soil erosion -Recycle all plant, crop and animal residues -Apply Phosphorus fertilisers, e.g. DAP, TSP, SSP -Avoid mono-cropping and continuous cropping -Apply liming materials, e.g. manure, agricultural lime, kitchen
Potassium, Calcium & Magnesium
► Soil erosion ► Continuous cropping Crop harvests ► Use of soil acidifying fertilizers, e.g. ammonium sulphate ► Potassium fixation
- Control soil erosion - Carry out crop rotation, improved fallows and recycle crop residues - Avoid practices that lead to soil acidification - Apply fertilisers that can add K, Mg & Ca, e.g. muriate of potash for K, CAN for Ca & N, dolomitic limestone for Ca & Mg.
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3.4.2 Soil phosphorus Phosphorus (P) naturally occurs as very sparingly soluble rock phosphate (apatite). A large proportion of P in apatite is unavailable to plants. Most tropical soils are highly weathered and therefore their phosphate reserves are very low. In addition, highly weathered soils tend to fix phosphorus, making it less available to plants. Because of this, phosphorus in most tropical soils is supplied through organic matter decomposition. In nature phosphorus is lost through a number of processes. These must be managed to sustain crop and animal production. These are summarized in Table 1.3.1. 3.4.3. Soil potassium, calcium and magnesium These nutrients mainly occur naturally in soils, but can be added through application of fertilisers, ash, compost and organic (plant and animal) residues. They are lost through soil erosion, crop harvesting and fixation (for K). Soil acidification also affects the availability of these nutrients. Table 1.3.1 presents various processes through which these nutrients are lost, and the different practices a farmer should carry out to control these losses and manage his crops better. 3.4.4 Micro-nutrients Soil micro-nutrients are commonly managed by maintaining soil pH in the range of 5.5 to 6.5. Thus, practices such as crop rotation, liming of acid soils and recycling of organic residues help to ensure a good supply of soil micro nutrients. Note: Most essential plant nutrients can be managed by controlling soil erosion hence the need to emphasize soil conservation practices. Continuous use of organic (plant and animal) residues promotes survival of soil microorganisms, which are the driving engine for a biologically, chemically and physically healthy soil medium.
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CHAPTER FOUR: SOIL FERTILITY LOSS AND POSSIBLE COPING METHODS 4.1 Soil fertility loss Soil fertility loss refers to the progressive loss of nutrients, leading to reduced crop growth and development. Soil fertility loss can occur in three main ways. These include: a. Soil erosion: This mainly affects the top soil layers b. Crop cultivation and harvesting: This leads to loss of soil nutrients as constituents of crop harvests c. De-vegetation: This is loss of vegetation from an area through deforestation, burning, ploughing, over grazing leading to soil fertility loss Soil fertility loss reduces crop yields and animal output, increases crop susceptibility to diseases and results in lower quality of crop produce. 4.2 Soil erosion 4.2.1 Types, causes and coping methods for water-induced soil erosion Soil erosion is the process of removal of topsoil by action of water and/or wind. It results in a progressive decline in soil productivity leading to reduced crop yields and animal outputs. Water-induced erosion can be sheet, rill or gully erosion, depending on the severity (Figures 1.4.1 to 1.4.13).
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Sheet erosion
Figure 1.4. 1: Sheet erosion in Namayingo district, Uganda Source: Semalulu O.
Figure 1.4. 2: Sheet erosion in Namayingo district, Uganda Source: Semalulu O.
Description – Soil movement caused by raindrop splash resulting in the breakdown of the soil surface structure and runoff (Fig. 1.4.1 and 1.4.2). – Occurs uniformly over the slope and may go unnoticed for some time. – Sheet erosion can be recognized by; soil deposition at hedgerows or the bottom of a slope; exposure of roots or stones; build-up of coarse (big) soil particles on the surface; or exposure of light-coloured subsoil.
Likely causes – Continuous cultivation – Soils that are bare through overgrazing are particularly susceptible – Soil compaction through overstocking, use of heavy machinery
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Coping methods – Crop rotation, contour cultivation, agro - forestry, intercropping, relay cropping – Control (reduce) grazing pressures – Maintain soil cover (minimum tillage, mulching, cover cropping) – Avoid bush burning
Rill erosion
Figure 1.4. 4: Deep rills. Deep rills can be found at slope bottoms where runoff concentrates Source: Semalulu O.
Figure 1.4. 3: Small rills. Small rills can be formed after a single storm,when the soil surface is bare or poorly covered Source: Semalulu O.
Description – Rill erosion results when surface runoff concentrates forming shallow depressions or small well- defined channels, normally less than 30 cm in depth (Fig. 1.4.3 and 4). – The small channels can be smoothed out (filled in by soil from the surrounding) by cultivation – Rills up to 30 cm deep are often easily visible in recently cultivated soils or areas cleared of vegetation. In tilled soils, rills often extend to the depth of the tilled layer – Rills are usually aligned along the slope (cut across the contour) and occur in a series of nearly parallel rill lines down the slope.
Likely causes – Common on agricultural land without vegetation and so is often seen in cropped areas after tillage – Following intense rainfall, cultivated top- soils overlying denser cohesive sub- soils often show rill erosion
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Coping methods – Planting grass around waterways – Diversion structures (channels constructed across slopes cause water to flow to a desired outlet) – Plant vegetation in the land around the rills to reduce runoff and consequently, the amount of water reaching the gully – Construct diversion banks, drop structures and retention dams, depending on the severity of the gully, in association with earthworks – Replace vegetation to stabilize banks and exclude grazing animals
Gully erosion
Figure 1.4.6: Gully in Mubende District, Source: Semalulu O.
Figure 1.4. 5: Gully in Mubende District, Source: Semalulu O. Description – Gully erosion is an advanced stage of rill erosion where surface channels have been eroded to the point where they cannot be smoothed over by normal tillage operations (Fig. 1.4.5 and 1.4.6) – The depth of the channels is over 30cm
Likely causes – Gully erosion often occurs on lower slopes,but can form in upper slope of the landscape in erosion susceptible areas
Coping methods − Retain vegetative cover on the soil surface to avoid leaving soil bare, especially during periods of high intensity rainfall.
– Areas commonly affected have easily erodible sub soils when exposed.
− Improve fallow by growing leguminous cover crops and crop rotation
− Keep land vegetated throughout the year (perennials are good).
– Reduce grazing pressure − Integrate soil management (soil bunds, cut off drains, water basins) with improved vegetation management (relay cropping, intercropping, agro-forestry) to maximize rainfall infiltration and use by vegetation.
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Soil erosion indicators Armour layer Fine soil particles have been selectively removed by erosion, leaving an armour layer of coarser soil particles concentrated on the soil surface. The thickness of the layer may indicate the severity of erosion.
Figure 1.4. 7: Armour layer, Rakai district Source: Semalulu O.
Rills
A rill is a shallow linear depression or channel in soil that carries water after a recent rainfall. Rills are usually aligned along the slope (cut across the contour) and occur in a series of nearly parallel rill lines. The small channels can be smoothed out (filled in by soil from the surrounding) by cultivation. In a particular area the total length, Figure 1.4. 8: Rills on bare slope soil, Rakai depth and width of the rills indicate the seriousness of erosion. Source: Semalulu O Gully A gully is a deep depression, channel or rift which is deep and wide enough and cannot be smoothed over by normal tillage operations. The length, width and depth of a gully can indicate the extent of accumulated erosion over time Figure 1.4. 9: A gully in a banana field, Mpigi Source: Semalulu O.
Crop/tree root exposure Plant roots may be exposed when soil around the base of a plant/tree are washed away.
Figure 1.4. 10: Banana roots exposed by erosion, Mpigi Source: Semalulu O.
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Rock exposure The underlying rock has been exposed at the ground surface because of soil erosion. When soil is washed away, marks/ stains may be left on the rock. The extent of soil erosion can then be estimated by the depth of the soil lost.
Figure 1.4. 11: Rocks exposed by erosion, Rakai district. Source: Semalulu O.
Soil colour
Soil colour is a simple but useful indicator of fertility. The colour of a particular soil is largely controlled by the amount of organic matter in the soil. Soils rich in organic matter are dark. Topsoil normally contains more organic matter and is darker than sub-soil. Severely eroded soils tend to be redder than the less eroded ones. Figure 1.4. 12: Change in soil colour after using mucuna green manure, Mpigi district Source: Semalulu O.
Exposed construction structure
Construction structures such as boreholes and house foundations may be exposed due to soil erosion as topsoil is continuously lost.
Figure 1.4. 13: Exposed borehole foundation in Mityana Source: Magunda.
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4.2.2 Effects of soil erosion • Soil erosion removes the most productive topsoil layer which has the highest amount of organic matter,biological activity, and nutrients. • Erosion decreases rooting depth and therefore reduces the amount of water, air and nutrients available to crops. • Erosion breaks down soil structure by selectively removing fine soil particles e.g. clays and small organic particles. Structure breakdown reduces water infiltration and further accelerates erosion. • Erosion makes tillage more difficult by forming gullies, exposing subsoil and rocks. • Loss of topsoil reduces the capacity of the soil to function and affects its ability to sustain future production 4.3 Crop cultivation Growing crops removes nutrients from the soil and when harvested, the nutrients are lost unless crop residues are recycled back to the farm. – Continuous cultivation with little or no use of fertilizers (organic or inorganic) leads to a progressive loss of nutrients, a process known as nutrient mining – Where land shortage is a problem, continuous cultivation with none or reduced fallow period reduces the time available for natural fertility regeneration – Different crops have different nutrient demands and mono-cropping can lead to mining of particular nutrients from the soil. • Coping methods – Return crop residues including ash and other organic materials (FYM) to the soil – Add organic and mineral fertilisers to the soil – Carry out crop rotation with legumes such as beans, groundnuts, soybeans – Carry out crop rotation 4.4 De-vegetation This is the process by which vegetation cover is lost from an area through deforestation, burning, ploughing, brick making and over grazing leading to soil fertility loss. a. Deforestation in this context refers to loss of forest cover through land clearing cultivation and tree felling for timber, charcoal, firewood, poles, fodder, medicine, food, etc. Deforestation can also be in form of shrub cutting and bush fires. Loss of forest/shrub cover exposes the soil to agents of erosion, leading to soil fertility loss. It also accelerates litter decomposition, further contributing to soil fertility loss. b. Burning destroys biomass, soil organisms, and exposes soil to agents of erosion, leading to soil fertility loss c. Ploughing removes biomass and exposes soil to agents of erosion. Poor cultivation methods (e.g. up and down the slope) contribute to soil fertility decline particularly in the upper part of the slope. Continuous use of heavy machinery for ploughing leads to soil compaction, which reduces water infiltration and increases runoff. d. During brick making, topsoil which is usually the most productive is removed and subsoil is exposed. In addition, fuel-wood is needed to burn the bricks. These processes impact directly on soil fertility. e. Grazing extracts mineral nutrients (fertility) from the soil. Overstocking leads to over grazing which exposes soil to agents of erosion
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Box 2: Possible coping methods for de-vegetation De-vegetation process Deforestation
Ploughing
Brick making Over grazing
Coping method - Incorporate soil & water conservation practices on the farm system - Plant trees (woodlots, forestry, agro-forestry), - Use alternative energy sources (e.g. energy saving stoves, biogas, saw dust, charcoal briquettes, solar) - Stop bush burning - Minimise cutting down trees - Practice minimum tillage; - Adopt improved tillage methods (e.g. along the contour not up and down the slope, use of herbicides). - Alternate heavy machinery with light technologies (e.g. animal draft) - Plant within crop residues (reduced tillage) - Remove topsoil from the target area prior to brick making, and return it afterwards - Use alternative construction materials (e.g. stones, sand bricks) - Optimize stocking rates - Zero grazing, - Improve local breeds; Plant improved pastures Rotational grazing
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CHAPTER FIVE: SOIL AND WATER CONSERVATION STRUCTURES 5.1
Relationship between precipitation, infiltration and runoff
Practical exercise: Demonstrate the relationship between precipitation, infiltration and runoff Procedure 1. Fill 2 basins to ¾ full with soil and level. 2. Tilt the basins to create a slope that represents the landscape commonly cultivated in the area 3. Fill two watering cans with water to half full 4. Fit one watering can with a horse having small holes and the other with large holes. 5. Using a watering can with small holes, water one basin 6. Ask to observe the relationship between precipitation intensity, infiltration and runoff 7. Using a watering can with a horse having large holes, water the second basin 8. Ask participants to observe the relationship between precipitation intensity, infiltration and runoff Key Message In the humid tropics, precipitation from heavy rains often exceeds the infiltration rate of soils leading to runoff, especially on steep slopes. Runoff causes soil erosion, leading to declining soil fertility and nutrient mining, and contributes to reduced productivity. Thus, soil conservation practices or structures should be put in place to divert, intercept, slowdown, store temporarily, or safely dispose of the runoff. 5.2
Effect of soil management practices on runoff and soil erosion
Practical exercise: Demonstrate the effect of soil management practices on runoff and soil erosion Procedure i. Identify 4 small plots(½ m x 1m) in a nearby location having different management practices: bare ground, mulched field, grass and crop (beans) field ii. Using a watering can, water the first plot until runoff is observed iii. Note the amount (volume) of water used iv. Repeat steps ii and iii for the other remaining plots v. Compare the amounts of water used in the four plots and discuss the findings Key Message On a bare ground, erosion occurs faster than on ground covered with mulch, crops or natural vegetation. A dense cover will minimize erosion much better than a light one. 21
5.3
Types of soil conservation structures
Practical exercise: Identify with participants, the different soil conservation structures There are two types of structures: 1. Structures that temporarily hold water as it infiltrates into the soil a. Those that change steep slope into a series of flat strips along contours across a slope for example terraces, ditches, contour bunds/dykes, built along contours b. Those that change a long (gradual) slope into a series of shorter slopes for example bunds or ditches. 2. Structures that drain runoff from the slope from where it has been concentrated, e.g. cut off drains, man-made waterways, gully control structures among others. Practical exercise: • Discuss the different soil and water conservation structures/practices and their purpose • Give description of soil conservation structures and illustrations/diagrams. • Give limitations of soil conservation structures/practices
Figure 1.5. 1: Roadside runoff water pits Source: RELMA
5.4 Types of water conservation structures It is vital to conserve the moisture already in the soil to minimize evaporation and leaching. Using mulch, organic matter and relevant structures e.g. terracing or their combinations, will help farmers to conserve the moisture. i. Retention ditches: These are small rectangular ditches dug in the ground across the slope with a level bottom and closed ends. These trap runoff and retain it for infiltration into the soil profile. They are most suitable in high rainfall areas
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ii. Basins: These are rectangular or square fields well levelled and surrounded with soil embankments. The embankments retain water that falls in the basins. Sometimes road runoff is directed into a series of basins constructed along a contour. These structures are suitable for crops like rice. They are suitable in high rainfall areas. iii. Roadside runoff canals: These are road runoff diversions constructed in a canal network along a contour. Pits are dug within the canal to trap sediment and allow water to infiltrate slowly in the soil (Figure. 1.5.1). Excess water flows into the next pit, connected by a tie ridge. The farmer scoops out soil after a storm and preferably puts it upslope. This is suitable in high rainfall areas. iv. V-shaped bunds (Negarims): These are small v-shaped earth embankments with the tip at the lower point of the slope (Figure. 1.5.2). Water is collected within the v-shaped basins and stored in the soil profile at the tip of the structure where the trees are planted. This method is best suited for trees/shrubs in low rainfall areas.
14 metres
Contour line
Runoff
10 metres Contour line
Slope
Figure 1.5. 2: V-shaped bunds (Negarims) Source: RELMA
V. Semi-circular bunds: These are earth embankments having a semi-circular or half- moon shape with bottom of the bunds on the contour (Figure. 1.5.2). Water is collected within the semi-circular basin from the area above it and stored in the basin. Excess water is discharged around the basin. The field layout provides for staggered basins so that runoff from the first row is intercepted by the second row and so on. These are suitable in low rainfall areas. Slope
6.5 m
Slope
3m
Plant hole Bunds
3.25m
Contour line Slope Runoff Slope
10-20 cm high
Figure 1.5. 3: Semi-circular bunds (micro-catchments) Source: RELMA
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vi. Trapezoidal bund: These bunds are earth filled embankment, trapezoidal in shape (Fig. 1.5.4). Tips of embankments are placed on contour line and the base along the lower contour. They are used for enclosing large areas and impounding large amounts of water. This method is suitable for driest areas (less than 400mm rainfall) with non cracking, deep soil and very gentle slopes of 2%. Contour line Run off
Runoff
Run off
Runoff
Runoff
Figure 1.5. 4: Trapezoidal bunds Source: RELMA vii. Planting pits (water pockets) These capture rainfall, runoff and litter (Figure. 1.5.5). Presence of litter attracts termites and other macro organisms which create channels in the soil. The channels facilitate water movement in the soil (infiltration/seepage). The planting pits improve soil fertility and water availability during dry weather.
Figure 1.5. 5: Planting pit (water pocket)
Figure 1.5. 6: Micro - basin
Source: RELMA.
Source: RELMA.
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viii. ix.
Micro-basins (Like Negarims) OR ‘Ngoro’ (Tanzania) These are small earth ridges in square or honeycomb pattern each side 0.5 – 2.0 m long (Fig. 1.5.6). Sometimes topsoil is put on the plant material forming these pat terns with holes at centre. They capture rain water from the field and collect arou plants, improve soil fertility, improve infiltration capacity and reduce soil erosion. Sunken beds Beds measuring 1.2m x 10m with paths 60cm wide between beds (Figure. 1.5.7). They trap and conserve water runoff.
Figure 1.5. 7: Sunken beds Source: RELMA
x. Runoff water harvesting pits Runoff from roads, waterways and gullies can be harvested and stored in pits lined with polyethylene sheets, tanks or ponds to be used for supplementary irrigation. The pits vary in capacity depending on the sizes of enterprises, labour, and duration of the rainy season or dry spell. xi. Compound water harvesting Water from the roof catchments can be harnessed and stored in tanks, cemented pits or pits lined with polyethylene sheets and used for domestic use, livestock watering or backyard garden irrigation (Figure. 1.5.8 & 1.5.9).
Figure 1.5. 81: Roof water harvesting Figure 1.5. 82: Compound runoff water harvesting Source: Semalulu O
Source: Semalulu O
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CHAPTER SIX: SOIL AND WATER CONSERVATION EQUIPMENT AND STRUCTURES 6.1 Types of field survey equipment Simple survey equipment is used in the construction of soil and water conservation structures. The equipment include: A-frame, Elgon level, Water Ring, Water Tube Level, Quick Set Level, Clinometers and Line Level. However, the quickest, simplest and commonly used is the Line Level. Thus in this manual, emphasis will be put on the line level. 6.2 Line level Components of the line level A line level is a simple instrument which is used for laying out contours and other simple soil surveying tasks. It is quick to operate, accurate and easy to transport. A line level consists of two boards, a cotton string, a spirit level and 2 anchors (triangular pieces of wood) (Figure.1.6.1).
a. Boards
Figure 1.6. 1: components of a line level Source: Rusoke
Figure 1.6. 2: Graduation board Source: Rusoke
The boards are made of hard wood each of 2.5cm x 4cm x 150cm. The boards are graduated starting with the zero mark about 5cm down from the top. Graduations are marked starting at 0 on top with intervals of 5cm, with a larger mark at each 10cm, down to the bottom of the board (Fig 1.6.2 & 1.6.3). b. Cotton string A cotton string of 11 metres is tied at1 metre on the board. Unlike nylon, a cotton string does not stretch hence ensures that the length remains constant. c. Spirit level The spirit level consists of a plastic or metallic tube containing spirit with an air bubble. It has hooks at each end.
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Setting up a line level Practical exercise Demonstrate how to set up and use a line level (Figure. 1.6.3)
Figure 1.6. 3: Setting up a line level Source: Rusoke Steps in setting up a line level i. Get three people ii. Tie a loop of string at the top (0 graduation mark) of the line level boards iii. Pull the string straight to the other board, leaving a distance of 10m between the two boards iv. Get a second person to hold the second board vertically v. Get a third person to hook the spirit level exactly onto the centre of the string vi. Align the two boards at the same height by moving the second board with the cotton string fixed at the 0-graduation until the air bubble is exactly in the middle of the spirit level. vii. Check accuracy of spirit level by removing it from the string and turning it upside down (180 degrees) and returning it in its original position and re- hooking it onto the string. viii.Check if the bubble has come to the centre again. If it has not, use another spirit level. Uses of a line level A line level can be used to determine: • Slope gradient (percentage of a slope), • Vertical interval (V.I) • Lay out of contours CASE 1: Determining the percentage slope (gradient/steepness) The percentage slope is measured to decide what type of structure and vertical intervals (V.I) should be used. Steps in determining gradient/steepness i. Get three people ii. Select a place that is representative of the field iii. Align the line level along the slope iv. Place the tied board down slope with the string tied at zero mark of the board v. Then place the untied board upslope. vi. Hold the string at the zero mark on the untied board 27
vii. Keep the string tight and move it slowly down along the graduation marks until the air bubble is at the centre of the spirit level. viii.Read the figure from the graduation mark on the untied board when the string is leveled ix. Convert the reading into metres x. Calculate the percent slope using the formula below: Slope % = [(Difference in height reading on the untied board in metres) x 100] divided by (Length of string in metres) Practical exercise Determine the percentage of different slopes using strings of different length In determining the percentage of different slopes, strings of different length are used. • For gentle slopes 0 to 15% use a string of10m long • For steep slopes of 31%-60% use a string of 5m long • For very steep slopes of more than 60% use a string of 2.5 m long. Determining the percent slopes using strings of different length Example 1: If 80 cm (0.8 m) was read from the untied board using a 10m string, the percentage slope will be: Slope% = difference in height on the board (0.8m) / (10 m string) x 100 = 8% Example 2: If 80 cm (0.8 m) is read from the untied board, using a 5m string, then: Slope % = difference in height on the board (0.8m) / (5m string) x 100 = 16% Example 3: If 80 cm (0.8 m) is read from the untied board, using of 2.5m string, the percentage slope will be: Slope % = difference in height on the board (0.8m) / (2.5 m string) x 100 = 32%
CASE 2: Determining Vertical Interval (V.I) and laying out contours for level channels A vertical Interval (V.I) is the difference in height from one terrace to the next. The V.I will determine the height (riser) of a developed bench terrace. A change in the V.I will affect the distance between terraces, called the horizontal interval (H.I). A larger V.I will increase the distance between terraces (H.I) and the height (riser) of the terrace, and vice versa. It is common to use a constant V.I. It varies from 1.5m to 2.0m. The measurements start from the upper end of the field, going down-slope.
A smaller V.I. should be used for more erodible soils, and the maximum H.I. should not exceed 20m. When measuring V.I. the length of the string is not defined and will therefore differ depending on the determined V.I. and slope gradient. If graded terraces are to be constructed, the Vertical Intervals are normally set out from the end nearest the waterway or 28
discharge point. Each V.I. point should be well marked, as the V.I. marks will be the starting point for layout of each contour. Remove the temporary marks to avoid mistakes. Procedure i. Decide what you should use. For deep soils with good infiltration, heavily mulched soils or those with a permanent cover crop, V.I. could be large. A smaller V.I. should be used for shallow soil, easily erodible and on steep land (so that the H.I. is also small). ii. You need three people. Let one person tie the string at the zero mark on the tied board. iii. Let another person lower the string on the untied board from 0 to 100cm mark. iv. You have now measured a 100cm (1m) vertical interval. Make a temporary mark on the tied board v. Let the person with the tied board move it up and down the slope keeping the string tight until the air bubble in the spirit level is at the centre. vi. Repeat the exercise by placing the person with the untied board at the temporary mark while the person with the tied board moves further down the slope (Fig. 1.6.4)
Figure 1.6. 4: Using the line level to determine the vertical interval Source: Rusoke
vii. Repeat steps 3, 4, and 5 viii.Place the spirit level at the midpoint of the string and let the person with the tied board move down-slope to a new position, keeping the string tight, until the air bubble in the spirit level is at the centre. You have now measured another 100cm (1m) vertical interval. The second measurement of 100cm (1m) will give the intended V.I. of 2m (100cm+100cm). ix. Place a permanent mark at the position of the tied board x. Repeat the above process down the slope until you reach the end of the farm Lay out contours as follows; • Hold the string at zero mark on both boards. • Tie the string on one board at zero mark. • Starting from the top of the field at the first Vertical Interval (VI) point pegged out, lay the contour across the slope. • The person with the tied board positions it (board) at peg 1 (Fig. 1.6.4) • The person standing by the spirit level directs the person with the untied board to move up or down hill, while keeping the string tight, until the bubble in the spirit is at 29
• • •
the centre and then drives a peg into the ground behind the untied board. Move the tied board to the new peg and repeat the process, along the contour up to the end of the field. Realign the fixed pegs to smoothen out the curve along the contour Dig a shallow trench along the smoothened curve.
Note: Contours should be laid smoothly across the slope to avoid sharp corners and depressions where water can break through and develop rills and gullies (Fig. 1.6.5).
Figure 1.6. 5: Location of contours for conservation structures Source: Rusoke CASE 3: Laying out contours for graded channels and drains Graded channels are used for draining excess runoff from cultivated land to a natural or artificial waterway. The layout of the channels depends on the steepness of the slope. For slopes of 5% and above (erodible/ loose soils) the 10m string is tied at 0- mark on the tied board and placed at 2.5cm on the untied board. For gentle slopes below 5% (stable soils) the 10m string is tied at 0- mark on the tied board and placed at 5cm on the untied board. Lay out of the channels is carried out the same way as for level contours, but the laying must start from the drainage point to ensure that run-off from channels drains into the intended drainage area. Layout of a cut off drain (with channel and a Fanya Chini bund) The purpose of this structure is to harness excess runoff water from the neighbouring land above a farm and prevent erosion. It may be constructed along a level or graded contour line. Step 1: The farm is surveyed by a trained person to establish the soil structure, slope, spacing of soil conservation structures and determine if a cut off drain is required above the field. Dig a trench (cut off drain) of 1.0 to 1.5m wide at the top and 0.75 to 1.0m wide at the bottom. Depth is approx. 0.6 to 1.0m. Heap the soil down slope/lower side of trench leaving a small step of 20cm between the trench and the bund (heaped soil) so that the soil is not washed back in the trench when it rains (Fig. 1.6.6).
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Figure 1.6. 6: Construction of a cut-off drain (Fanya chini) Source:Rusoke
Note: The runoff from outside the farm is held and infiltrates into the soil through the trench. Where runoff water is overwhelming, the trench should be connected to an artificial or natural waterway to dispose off excess water.
Layout of fanya-Juu terraces (for farm conservation) These terraces develop from ‘fanya-juu’ bunds which are built by throwing soil from the channel up the slope (Fig. 1.6.7). They reduce runoff and improve water infiltration to thesoil. Ploughing, weeding and natural soil movement causes the land between terrace banks to level off into benches after a few years. These are suitable in marginal/ high rainfall zones (700mm rainfall & above) with deep soils and for slopes from less than 5% to 50%.
150 cm 50 cm Soil upslope
50 cm
60 cm
Figure 1.6. 7: Construction of ‘Fannya-Juu’ bund Source:Rusoke Step 2 (i) Survey contours with a line level. Spacing of the terrace banks is usually between 5 and 20 meters apart, depends on the slope of the land: the steeper the land, the closer the terrace banks). (ii) Dig soil along a contour and throw it upslope to prevent soil coming down the slope to make a bund (heaped soil or dyke). The trench is 60cm wide and 60cm deep. Leave a small step of 20cm between the trench and the bund so that soil is not washed back in the trench when it rains. (iii) Each bund is 50cm high and 150cm wide at base with 30-45cm tie bunds every 5 to 10 meters along the trench. A tie bund is an undisturbed strip of soil 30-45cm wide, left along the trench, 10-15cm lower than the soil surface. It checks the speed of runoff and ensures uniform distribution of runoff water along the trench. 31
(iv) Plant grass on top of the bund to stabilize it. (v) Ploughing, weeding and natural soil movement cause the land between the terrace banks to level off into benches after a few years.
6.3 The A-frame The A frame is another survey equipment used for citing and laying out contours. However it is slow and tedious to use especially in big fields. For this reason it is not described in this manual due to the challenges associated with its use.
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CHAPTER SEVEN: AGRONOMIC/CULTURAL CONSERVATION FARMING MEASURES
7.1 Introduction For soil and water conservation structures to be effective, they should be used in combination with biological and agronomic/cultural practices and systems. Agronomic practices are in essence, proven techniques of soil management. 7.2 Conservation farming practices Conservation farming means rducing erosion through good crop husbandry. Conservation farming may be carried out through a number of practices including: a. Contour ploughing and close planting For erosion control, contour cultivation (across the slope) is better than the up- and- down the slope. However, merely planting crops along the contour will not significantly reduce soil loss and runoff. Close planting (which leads to quick dense ground cover and retards soil loss) along the contour will yield better results whilst planting crops on contour beds on slopes below 12% and on permeable soils controls erosion and runoff even better. Integration of structural measures with close planting gives better results in both yield and soil erosion control. b. Correct spacing This is a farm practice where the crops are given correct horizontal space (within and between rows) so that there is minimum competition for water, nutrients and space for the canopy. This enhances plant development and strong growth providing cover and protection to the soil from splash or wind erosion. c. Strip cropping Strip cropping is a conservation practice in which crops are grown in a systematic arrangement of strips or bunds that serve as barriers to water and wind erosion. This practice is more effective under mild rainfall and on gentle slopes of up to 15%. It should be supported with structural measures. There are three major types/designs of strip cropping. These are Contour Strip Cropping: Two or more crops are planted along contours in alternate strips. i. Field strip cropping: The alternate strips are of uniform width across the field and do not necessarily conform to the contour. This is used on very irregular topography. ii. Wind strip cropping: Tall, wind- resistant crops and normal crops are planted alternately in narrower strips perpendicular to the direction of prevailing winds. d. Timely planting After land preparation, seeds should be sown as early as possible to avoid soil being left bare for a long time. By the time the rains intensify, the crop canopy will have developed to reduce the impact of rain drops to the soil. e. Multiple cropping This is a practice where a farmer plants several crops on the same piece of land at the same or different time period in a cropping season (Figure. 1.7.1). This is done to ensure maximum use of both horizontal and vertical space hence proper canopy cover and soil protection from sun heat, wind and rain drop splash erosion. f. Trash lines These are structures formed by arranging or heaping vegetation materials in a line along the contour to check runoff. After crop harvest the materials on trash line can be distributed and mixed in the soil hence adding more organic matter. 33
g. Stone lines These are structures formed by arranging or heaping stones 25-30cm high and 30- 40cm wide at the base in a line along the contour to check runoff. Stone bunds/lines are spaced 15m-30m apart. Contours are surveyed using a line level starting at the top of the field and working down the slope.
A shallow foundation trench is dug along the contour for each bund. Construction begins with large stones in the rear of the trench (down slope side). Smaller stones are used to build the rest of the bund (Figure. 1.7.2). The stones must be packed carefully, especially at the bottom. Soil from the trench is piled up in front of the bund and the stone bunds are left for a year to catch sediment. Stone lines slow down runoff, encourage deposition of soil and reduce erosion. Grasses and tree seedlings are planted alongside the bund. Stone lines are used widely, on cultivated land and also barren land which is to be used in future- where the soils are shallow and where stones are available
h. Mulching Mulching is protecting the soil (on slopes up to 15%) with plant residues, straw, green leaves and stems, and even gravel against splash erosion, wind erosion, capping and extreme temperatures. Mulching provides organic matter which supports micro-organisms, soil nutrient supply and minimizes loss of nutrients. The mulch also reduces soil moisture loss and enhances water infiltration. Mulching can be applied over the whole field; between crop rows or along the contours; or around single plants in case of tree crops (Fig. 1.7.3 & 1.7.4). Mulching can be applied in many ways- where plant residue from previous crop harvest is cut and spread over the field as stubble mulching (crop residue chopped and spread over soil surface). Farmers should be encouraged to grow their own material or practice live mulching and minimum tillage. i. Cover cropping Cover crops are close-growing crops planted mainly to protect soil (on slopes of 15 to 50%) between tree crops or semi- permanent crops or between the seasons for regular crops. Cover crops can be legumes or grasses, depending on the actual needs. With dense cover and roots, cover crops can be very effective in erosion control (Figure. 1.7.5). However, cover crops may compete for moisture and nutrients and affect yields of the main crop. Special management such as timely cutting of foliage, circle weeding and probably more fertilizer inputs are needed. j. Minimum tillage Minimum tillage is the practice where field operations are carried out with minimum soil disturbance, sometimes referred to as conservation tillage. It involves tilling only the crop zones for seed planting, germination and crop establishment. It may also involve mulching with crop residues, use of special equipment and herbicides etc., depending on various conditions. k. Vegetation barriers These are bushes or hardy grasses planted as a barrier across a gentle slope in order to retard soil from being washed down slope (low rainfall areas). Grass strips and live fences fall in this category. There are two general approaches. 34
Figure: 1.7. 1: Multiple cropping Source : Semalulu
Figure: 1.7. 4: Sketch of mulching in
Figure: 1.7. 2: Stone bunds Source : Semalulu
Figure: 1.7. 5: Mucuna used as cover crop
Figure: 1.7. 3: Mulching in a banana field
Figure: 1.7. 6: Raised bed
banana field Source : Banana Program
Source : Semalulu
Source : Semalulu
Source : Semalulu
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l. Partial weeding Circle weeding around fruit trees, flowers or bananas is usually sufficient especially when trees or plants are planted in individual basins. For plantations of tea or coffee, etc. strip weeding can be applied, leaving the inter space as a grass buffer. Occasionally, the grass should be cut, but there is need to dig it out. m. Deep ploughing, This is the cultivation of topsoil and subsoil to a depth of 30cm - 60cm depending on soil, crop requirement and the tools to be used, in order to: • Break soil crusts, hard pans, etc. • Provide spaces for air and water in the soil for crop growth, • Increase water infiltration • Promote earthworm and microbiological activities, • Develop better soil structures, especially with added organic matter. The crops may be planted on raised beds (Fig. 1.7.6) in high rainfall areas or sunken beds (see Fig. 1.5.7) in low rainfall areas. Integrating mulching, compost manure application and irrigation makes this system produce most effectively throughout the year. n. Use of compost and farm manure This is a practice where a farmer makes use of manure from the kraal, zero grazing unit, poultry unit or pig sty mixed with crop residues and kitchen refuse either directly or after composting. This helps to recycle soil nutrient on the farm enhancing sustainability. Addition of compost and farm yard manures to the soil improves soil fertility, aeration, structure and biological life.
Small farmers can make compost in pits or piles in the open air. The site should be near enough to the area of application to reduce future transportation chores. Compost is built by putting down alternate layers of plant material and farm manure (Figure. 1.7.7). The whole mass should be kept moist in order to reduce the loss of ammonia and to encourage vigorous bacterial action. Sometimes phosphate is also added to balance the mixture and make it more effective. The composting mass should be turned twice after every 3 to 4 weeks to maintain aeration and promote microbial activities. Attention should be taken not to let too much rain water soak in; any solution from the compost should be collected and eventually used for fertilizing. Allow to decompose until the stick (thermometer) feels cold when removed, indicating the process is complete. Since the whole process needs considerable labour and time to make and collect/use, farmers should use it selectively.
o. Use of green manures, This is a practice of ploughing into the soil green plant material when at the flowering stage improve the soil structure, replenish plant nutrients, and minimize runoff and erosion. Many leguminous crops are used for this purpose to supplement compost and farm manure. p. Use of fertilizers Where soils are proved to be deficient in important nutrients (Nitrogen, Phosphorus and Potassium) a farmer is advised to seek technical assistance to apply recommended commercial/mineral or organic fertilizers to correct the deficiency. Proper application of fertilizer will improve soil fertility and promote faster crop cover to protect the ground from splash or wind erosion. This is important especially on degraded and newly reclaimed 36
land or terraces. Because of its high cost, fertilizer should be used selectively by the small farmer. It is best to use fertilizers in conjunction with compost, farm manure, and green manure sometimes referred to as integrated soil fertility management. For proper use of fertilizers, it is important apply the Right source of nutrients at the Right rate, at the Right time, and using the Right method. For further guidance the reader is referred to Kaizzi et al., 2010. Use of the Fertilization Tool (FOT) which was developed by NARO to give economically optimum fertilizer rates where the farmer will obtain the maximum economic benefit. The computer, paper and mobile versions are available and downloadable to the computer from the following website address: http://www.agronomy.unl.edu/OFRA.
q. Crop rotation This is the growing of different crops in recurring succession on the same piece of land in a planned cycle (Box 5). The best system will depend on the farmer’s preference, economic advantages, and physical environment. The farmer should include legume/grass mixtures to enrich nutrient reserves and improve soil structure. Unlike mono-cropping which depletes soil nutrients and increases pest and disease hazard, rotations also give small farmers a variety of crops for diverse use as well as flexibility in marketing. This system suits well in the socio-economic needs of the small farm holdings; however not many farmers know how to apply it. ‘Thermometer’
Soil Up to 1.5 meters high
Animal manure Kitchen ash Soil Plant residues Maize stalks at the bottom
Figure: 1.7. 7: A sketch of compost making Box 5: Example of a crop rotation sequence Year 1 Season
Season 1
Season 2
Year 2
Year 3
Virgin land Start with a heavy feedercereal (maize, rice, sorghum etc.) Plant a light feeder – root crop (sweet potatoes)
Continue with a light feeder from season 2 of year 1 (sweet potatoes) Plant a heavy feeder – legume: soy beans, dry bean soy beans, groundnuts, etc.)
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Plant a light feeder- root crop (Cassava, yams)
Continue with light feeder from season 1 (cassava)
CHAPTER EIGHT: INTEGRATING SOIL CONSERVATION WITH FARMING SYSTEMS 8.1 Introduction For soil conservation to be successful, it should be well-integrated with the prevailing farming systems and become an indispensable part of the overall package of measures being advocated. Below are some examples: 8.2 Hillside farming and conservation farming systems Conservation farming is a system of farming which protects the land from any form of deterioration yet increases or maintains farm production to the benefit of the farmers. 8.2.1 Agro-forestry This is a system where trees/shrubs, are deliberately grown on the same piece of land with crops, fodders or animal (Nair, 1983). Commonly recommended agro forestry trees and shrubs are: Albizzia, Grevilea, Sesbania, Calliandra, Leuceana, among others (Figure. 1.8.1).
Figure 1.8. 1: Example of Agro-forestry practice Source: Semalulu O.
The main purposes of Agro-forestry are; a) To use agricultural crops or pasture as a transitional means of utilizing the land until forest plantations are fully established b) To bring trees and shrubs, into the farming systems, to the benefit of both crop production and resource protection. Agro-forestry can be beneficial to small farmers in many ways e.g. fuel wood, poles, fodder, mulching material, shade, medicine, food, windbreaks to crops, etc. For more detailed information refer to Volume I, module 3. 8.3 Pasture management on slopes Small farmers use land mostly for cultivation of food and cash crops. A small portion of a farm may be left to fallow when continuous cropping is found to be unrewarding. Cows, draught animals, or small ruminants are usually grazed on the fallow land. These animals are also turned loose for grazing on roadsides, stream banks or any other public land.
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In establishing or rejuvenating pasture on slopes or rolling land, simple conservation structures are sometimes needed to prevent erosion from heavy rains and runoff during the early stages when the land is not well covered. Their spacing, however, may be double or triple of those used for agricultural crops. Diversion ditches are sometimes used to intercept large quantities of runoff coming from the slopes above. Mulching should be practiced for reseeding pasture on steep slopes to prevent the seeds from being washed away and for a better and even germination. Suitable fertilization or liming is often needed to help pasture establishment e.g. use of rock phosphates/super phosphates on soils with low pH (acidic). Pasture of mixed grasses and legumes usually provide more diversified and nutritious forage for various animals and maintain better fertility. Once pasture is established, controls on utilisation are necessary. Three grazing options are discussed: a)
Zero grazing: Zero grazing is the practice of keeping domestic animals in a confined unit from where it is stall-fed (Figure. 1.8.2). This practice is especially applicable in densely populated urban/ peri-urban areas, wet seasons and steep slope areas.
Figure 1.8. 2: A farmer feeding cattle under zero grazing (Source: Semalulu O).
b)
Controlled grazing: This means controlling the number of animals on a unit piece of land. The carrying capacity of the land (1-2 acres per animal) should not be exceeded unless other sources of feeds are available. For community pastures certain public controls are needed.
c)
Rotational Grazing: Is a system of pasture utilization consisting of a short period of heavy or normal stocking followed by periods of rest for plant recovery during the same season. Fertilizers or manures are needed for quick recovery. For more detailed information refer to Volume 2, module 1, chapter 4 and module 6 chapter 1.
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REFERENCES Assmo, P. and Eriksson, A. (1995). Soil conservation in Arusha region, Tanzania. Manual for extension workers with emphasis on small scale farmers. RELMA. Hai. M.T. (1998). Water harvesting: An Illustrated manual for Development of Micro catchment techniques for crop production in Dry Areas. ISBN 9966-896-33-3. Kaizzi CK., Semalulu O., Ssali H. and Byalebeka, J. (2014). Soil Fertility Management in Uganda. A Training Manual. Kaizzi, C.K. and Wortmann, C.S. (2016). Optimizing fertilizer use within an Integrated Soil Fertility Management Framework. Fertilizer Optimiser Training Manual. Nair, P.K. (1983). An introduction to Agroforestry. World Agroforestry Centre/ICRAF. Klgwer Academic Publishers. http://www.worldagroforestry.org/Units/.../32 Rusoke, C., Nyakumi, A., Mwebaze, S., Okorio, J., Akena, F. and Kimaru, L. (2000). Uganda Land Resources Manual: A guide for Extension workers. RELMA.
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MODULE 2
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FORESTRY (TREE NURSERY MANAGEMENT, TREE PLANTING AND AGRO- FORESTRY)
Grace Abigaba (NaFORRI) George Niyibizi (NaFORRI) Grace Rwabaingi (PRIVATE SECTOR)
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CHAPTER ONE: FORESTS AND WOODLANDS 1.1 Introduction Forests, trees and woodlands are important resources and they play multiple ecological, economic, social and cultural roles. Forestry makes a substantial contribution to the nation’s economic development and well-being, although the extent of this is not fully recognized. This therefore suggests that there are many opportunities for poverty alleviation, for economic development and for environmental improvement through forest sector development. Generally, it is recognized that forestry is very important through its contributions to; a. The national Gross Domestic Product b. Provision of forestry products c. Creation of employment d. Provision of subsistence needs e. Provision of environmental services and bio-diversity f. Much of the tourism in Uganda is based on forests, woodlands and their constituent wildlife and natural beauty. However, the main issue is how to capitalize on the economic, social and environmental opportunities in forestry without undermining (degrading and over-exploiting) the resource base. A lot of deforestation has occurred in the last 50 years. This has been mainly due to the rapid population increase which has not been coupled with parallel economic and technological development. 1.2 The following activities have contributed to the environmental degradation a. Clearing forests for agricultural development b. Cutting of trees for charcoal production c. Collection of firewood for domestic as well as for commercial purposes d. Burning of forests e. Over-grazing by livestock in some areas like in the cattle corridor. f. Degradation of wetlands Some of the consequences of deforestation a. b. c. d.
Shortage of construction poles and timber Fuel-wood problems in some areas Shortage of fodder esp. during dry season Silting and flooding of rivers and streams
e. Declining soil fertility leading to low crop yields f. Increased soil erosion
Efforts to reduce the rate of cutting down trees for both charcoal and firewood include: a. Agroforestry initiatives b. Use of energy saving stoves c. Briquette making d. Use of solar cookers e. Tree planting
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CHAPTER TWO: TREE NURSERY ESTABLISHMENT AND MANAGEMENT 2.1 Introduction
Availability of good quality seed on time is a pre-requisite for all tree planting activities. The way seedlings are handled and managed in a nursery contributes to their survival rate after planting and their subsequent growth performance. Improving seedling quality correlates positively to their survival, growth and productivity. Nursery practices must be consistent and the various techniques closely integrated. If one element in the chain is lacking there will be a negative impact on seedling quality. Good quality seedlings cannot be produced without care and tending. Nursery plants need to be protected from extremes of environmental conditions until they are strong enough to ensure high quality of seedlings and to provide more opportunities (income, technology transfer). Local people are encouraged to establish small-scale community nurseries.
2.2 What is a tree nursery?
A nursery is a place where seedlings are propagated, managed and grown to reasonable transplanting size (Fig. 2.2.1). To ensure a good planting program, good nursery stock is necessary as it produces seedlings for agroforestry, afforestation and reforestation and other tree planting activities. The purpose of a tree nursery is to grow seedlings: – Of the required plant species – Of the required age, size and sturdiness – In sufficient quantities for the intended tree planting programs – At the most favourable time of planting
Figure 2.2. 1: Photo of a tree nursery Source: NaFORRI 2.2.1 Types of tree nurseries i. Temporary or permanent A temporary nursery is established if the planting period is lasting not more than 1.5 yrs. It can be used for three seasons only, and is abandoned after fulfilling the aim of the planting program. ii. Permanent nursery This is the type meant to serve for a long period of time. In this case, seedlings are raised 44
from year to year, e.g. central nurseries for research and training institutions. Some privately owned commercial nurseries are run on a permanent basis. 2.2.2 Tree nursery terminologies a. Seedbed: An area in the nursery where seeds are sown and germinated. b. Transplants: Young seedlings which have been pricked out from the seed bed into the transplant bed. c. Pricking out: Is the operation of lifting young seedlings from the seed- bed to the transplant bed. d. Transplant bed: An area in the nursery where young seedlings which have been pricked out are cared for. e. Propagation: Is the production or multiplication of a plant using its parts. These could be seeds, stem cuttings, roots, branches and sometimes leave. f. Viability: Ability of the seed to germinate. 2.3 Nursery Establishment 2.3.1 Nursery planning When establishing a tree nursery, various aspects have to be taken into account. These include; size, location, availability of water, skilled labour force and market for the seedlings to be raised in the nursery. A nursery site is a very important point to consider before starting because it influences the effort that will be required to maintain it, the way in which it will be managed, and the ease of access to users. 2.3.2 Factors to be considered in selecting the site for a nursery i. Availability of land: The selected nursery site should have enough land to raise the number of seedlings needed, and if possible, room for expansion. The size of a nursery depends on the number of plants to be produced and the time they will remain in the nursery. ii. Land ownership: Before establishing a nursery, it is important to ascertain who owns the land. If it is institutional or privately owned land it is advisable to formalize the use of the land by obtaining a letter from the owner agreeing to its use as a tree nursery for a defined period of time. For communal nurseries, the land should preferably be public land. If privately owned, a binding agreement must be made between members of community and the owner. iii. Permanent Water supply: A reliable and adequate water supply is always a requisite in nursery establishment. The nursery site should be located near the source of clean water either from a running stream or main pipe water supply to sustain rapid and healthy growth of the seedlings. Alternatively, a water storage tank should be installed for sustainable water supply. iv. Topography: The area for tree nursery establishment is preferably flat with a gentle slope to allow for drainage. Contour terracing should be done if the slope is in excess of 2 per cent. v. Accessibility: The site should be accessible all year round, so that customers are able to get seedlings easily as well as for transportation of mature seedlings to planting sites and or markets. The site should be near to the road and as close as possible to the centre of the area to which plants will be supplied. vi. Availability of labour: A lot of labour is required for the construction of a nursery and subsequent nursery activities. Hence nurseries should be located where labour is available. Siting a nursery on a main road near a village will also increase awareness and enhance patronage. 45
vii. Soils: Deep, good structured soil is desirable. Avoid shallow soils with a hard sandstone band near the surface. A very sandy-structured soil should also be avoided because of poor moisture retention characteristics and faster leaching of plant nutrients. Soil containing too much clay has poor drainage characteristics and should not be considered for a nursery site. 2.3.3 Basic tree nursery facilities A good nursery should have; i. Access roads and path Access roads and path facilitate easy movement of seedlings from seed beds to transplant beds and also for smooth movement of workers doing nursery operations such as routine watering, root pruning, sorting etc. should have pathways to all parts of the nursery. ii. Fencing It is necessary that all animals are totally excluded from the nursery. A live fence of thorny shrubs, barbed wire or chain link fence of 1.8m high is ideal. iii. Shelter Shelters for tools, materials and workers should be constructed if the nursery is not located near a homestead. iv. Seed beds These are usually made for seeds which cannot be easily sown directly in the transplant pots. Such seeds are first sown in these nursery beds and after germination; they are pricked out and transplanted into transplant beds where they attain plantable sizes. • When do we use seedbeds? – When seed is old or when the germination is low or unknown, use a seedbed to test viability before filling too many containers and wasting resources, – If seed does not store very well (that is if it is “recalcitrant”), – If containers are not available, or not filled in time to use, seedbeds can be used until the containers are ready. • Some common problems associated with seed beds – Using unskilled labour in pricking out always results in deformities, – When plants are left in the seedbed too long (which often happens), they produce long roots that are easily damaged or twisted when pricking out, – Many seedlings suffer a “shock” when they are transplanted from the seedbeds, v. Transplanted bed This is where seedlings are transplanted after pricking out from the seed beds and/ or directly sown. vi. Shading and shelter for plants These are made above the beds to protect the delicate seedlings in the transplant beds from too much sunshine or hailstorms. Papyrus mats or elephant grass can be used. vii. Sources of soil materials Sources of various soil components to be used in soil mixing should be put under consideration. Transportation of soil materials not at the site is a paramount. viii.Wind breaks Trees should be planted around the nursery to guard the nursery against strong winds. ix. A compost area This is an area where plant remains are collected for decomposition to make manure. x. Working area A good tree nursery should have a specific reserved area where workers can sit as they do their work. It is better for the working area to have a shelter. The main activities done here include; pot filling and pot cutting. 46
2.4 Nursery site preparation and layout 2.4.1 Materials and equipment needed for Nursery establishment include: • Wheel barrows, Jerry cans, watering cans, rakes, pangas, hoes and spades • A number of containers can be used, for example, polythene tubes, empty milk packets, tins and banana fibres. • Poles, timber, grass, papyrus mats and nails are also needed for shade stand construction. 2.4.2 • • • • • • • •
Nursery site preparation Steps followed for site preparation: Cut all the trees to a radius of 10 meters beyond the proposed boundary. Remove all the stumps and burn all the trash that was left behind. Destroy any termite mounds and remove all clay soils that are associated with them. Dig up or plough the area thoroughly well, removing any large stones and roots. Peg out the location of blocks and alignments of roads and beds within the area. Level each block using a levelling board, you can bring in soil from nearby areas to fill deep depressions. You can establish short grass to stabilize the soil. After sometime, a certain amount of settlement may take place and if this has happened, level the blocks again using discarded soils.
To obtain the maximum effect of the shade, beds should be orientated to run East- West to avoid direct sunshine. During March to September when the sun is in the northern hemisphere the shade should slope towards the north and the rest of the year when it is in the southern hemisphere, it should slope towards the south. If the sun is strong in the morning or evening, vertical shade can be constructed at each end of the bed. 2.4.3 Nursery layout This should be in such way that commonly frequented areas like offices, water sources, pot filling area and seed beds are centrally located. Transplant beds can be located around these for easy accessibility as shown in Fig. 2.2.2. It is more convenient for beds to be 1m wide and preferably not more than 20m long for easy management. It is better when beds are arranged in blocks. Width between beds may be 1M. Roads can be 4.5 m wide depending on the size of the nursery.
SB = Seed bed TB = Transplant bed CP = Compost pit WS= Water source FP = Foot Path
Figure 2.2. 2: Nursery layout Source: NaFORRI
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2.5 STANDARD NURSERY OPERATIONS AND MANAGEMENT
Most nurseries adopt operations which are standard; some operations are common to all nurseries although there could be some modification from one nursery to another. Good hygiene of the nursery site is quiet important. This will lead to healthy and quality seedlings produced in the nursery.
Good nursery hygiene practices include; – Disinfect the tools (knives) used in root pruning and drums used for collecting water – Regularly overhaul the substrates in the seedbed mixture to ensure continuous nutrient supply to the young germinating seedlings – If you are using grass or papyrus as shade, do not allow it to get rotten before you remove it – Control of the weeds in the nursery might reduce the invasion of some pests to the nursery – Always remove discarded and used old materials from the nursery to maintain the cleanliness and to avoid these materials to be used as entry points for pests and diseases. Soil mixing Good seed bed soils have two attributes: Ability to drain freely but retain enough water – Standard seed- bed soil mixture (SSM): This is composed of 50% sieved black forest or top soil and 50% sieved sand. The ratio of soil to sand should be 1:1. Forest soil gives sufficient moisture holding capacity to promote good germination whereas sand gives very porous, textured soil which allows good penetration of the roots of the germinating seeds and easy lifting when pricking out. – Standard transplant bed mixture (STM): This mixture of soil is used in the transplant bed or polythene tubes to give seedlings the most favourable growth conditions. The recommended mixtures are as follows; • 60% Un-sieved forest soil, 10% sand, 10% small stones (1cm diameter), 10% clay and 10% composite manure. • Sand and small stones give good root penetration and drainage characteristics, • Clay and top forest soil assist in binding near the roots to improve on the moisture intake and nutrient retaining qualities. • Composite manure, supplies organic matter and nutrients to the soil. In addition to the above mixtures, 20% of Mychorrhiza soil should always be added whenever Pinus tree species are to be raised. Mychorrhiza soil is got from a well- established pine plantation. The above mixtures can be left to mature for 2-4 weeks before use. However it should be kept moist. Note: soil mixtures above are adjustable depending on the availability of soil types at the nursery site. Pot filling This is the filling of polythene tubes with soil. It should be done under a shade near the heap of the soil at the site of the transplant bed. Soil must not be too dry or too wet but moist enough to run freely into the tube and can easily be firmed to form the bottom of the tube. Soil mixture should be pressed into containers to a depth of three-quarters the height of pots. Pots should then be loosely topped up with soil mixture and pressed down slightly at about 2 cm below 48
the top (Fig. 2.2.3). Heavy compaction at the top of pots should be avoided. It inhibits root penetration.
Figure 2.2. 3: Example of good pot filling. Source: NaFORRI 2.6 SOWING SEED Methods of sowing seed Seed sowing varies according to the size of the seed. a. Broadcasting: This applies to small sized seeds. The seeds are spread on top of the SSM, either by hand or mechanical broadcast. b. Drill sowing: This is the method of making shallow lines or drills in the SSM into which seeds are linearly dropped and lightly covered with SSM. • Procedure for sowing seeds in the seedbeds – Level the seed bed, – With fine seed such as Eucalyptus spp or Bottle brush, mix seeds with about twice its own volume of clean dry sand – Spread the seed/ sand mixture evenly over the whole area – Cover the seed with a layer of clean dry sand twice its own depth – Firm the covering and water lightly using a can with a fine rose or sprinkler – If any seed shows through the covering of sand, use another light layer of fine sand to cover the seeds. – Continue watering twice a day, very early in the morning and late in the evening until the seed germinates – Do not sow seed too thick. – Direct sowing: This method is used when sizeable large seeds are directly sown into containers. Direct sowing of seeds saves time, labour and money, because the extra step of preparing a seedbed and transplanting is eliminated. Even if it takes a little longer to plant small seeds directly in the containers, it is easier and cheaper than pricking out. Direct sowing allows undisturbed seedling growth and thus reduces stress of the seedlings. • – – –
When using direct sowing into containers, follow steps bellow: Prepare containers and shade in advance Test seed for viability before sowing. If less than 70% germinate, plant more than one seed per pot. If both germinate, prick out one into another container Pre-treat seed if necessary to speed up germination 49
Whenever possible, directly sow seed into containers to avoid root deformities. 2.7 WATERING A regular clean water supply is essential for plant growth. When grown in containers, seedlings have only limited volume of substrate and cant access water from far below the soil surface. • The amount of water for watering depends on: – Seedling age, – Amount of sunlight, – Soil type – Turbulence (presence of wind). • Avoid the following type of water in the nursery – Dirty water as it contains many plant diseases, – Salty water as it has high concentration of dissolved minerals including possibly toxic elements from natural deposits containing oil. – Very acidic or very alkaline. Occasionally clean water tanks and disinfect with a disinfectant i.e. Clorox to remove plant diseases. Note. Ensure uniform watering of all the seedlings including those on the end rows and along the sides of the seed beds. • Some of the good nursery watering practices include – Regularly check the water status of the leaves to determine when to water, – Water in the early morning and / or late in the evening, – Water the substrate thoroughly and not the leaves, – Water slowly and check that the water penetrates to the bottom of the container. • Some of the poor nursery watering practices include: – Directing the water to the leaves and not the soil – Watering during mid-day – Watering quickly and only wetting the soil surface. • Other points to note: – Over watering weakens plants and causes many diseases, – If the soil is covered with green moss or algae it means you are watering too much. NB: Be prepared for diseases like dumping off which can wipe out thousands of pine seedlings in a few days. Copper oxychloride is the standard precautionary treatment. Avoid too much dampness in the nursery to control spread of dumping off. 2.8 Pricking out This is the act of lifting seedlings from the seedbed into the transplant bed or pots. Only those who are trained in correctly pricking out should attempt it. Close supervision is necessary in order to avoid root deformities. Always check a few containers after a few days to ensure that it has been done correctly. • The Pricking out process – Ensure that the area where the transplanted seedlings will be kept is well shaded before you begin thinking of pricking out, 50
– Disregard any seedlings that appear sick or deformed, – Transplant when the tap root emerges or when seedlings have shown two or three leaves, before secondary roots are formed, – Water the pots well, one night before and one hour before pricking out so that water penetrates to the bottom of the seedbed, – On days with strong sunshine, prick out in the early morning or late in the evening, – Use a stick to gently loosen the soil around the seedlings by grasping their cotyledons or lower leaves – do not lift them out by the stem as it is still tender and fragile, – Put seedlings in water and keep them under shade as soon as you take them from the germination bed, – Prepare planting holes with a stick and ensure they are sufficiently wide and deep, – Clip long or very branched roots to ensure they are pointed downwards, – Gently pull the seedling upward after placing it in the hole, to straighten out roots, – Pack the soil against the roots, starting at the bottom of the hole, – Water the plants immediately after transplanting and continue watering as conditions demand, – The whole operation should be carried out under shade. • Poor common pricking out practices include: – Waiting until plants are large and have long roots, – Pricking out plants into dry soil and then watering them, – Constructing shade after pricking out is done, – Pricking out in direct, hot sunlight, – Transplanting damaged seedlings, – Removing seedlings by grasping the stem may permanently damage water flow – Carrying seedlings in your hand or on a plate without water, – Preparing the holes with a finger – the hole might be too small or too big depending on the size of the finger used, – Allowing roots to bend upwards when inserting them into the hole, – Leaving air pockets around the roots, plants will die. 2.9 Shade After pricking out, transplants require full shade for the first 2 – 3 weeks, then half shade for 1 week, after which no shade should be necessary. As the shade is decreased, the intensity of watering must be increased. For the first days after pricking out, light watering is necessary, similar to that given to a seedbed. Once the plants are established and fibrous roots begin to develop, the rate of watering should start increasing gradually. 2.10
Weeding
This is the operation of removing weeds in order to reduce competition for water and nutrients so as to enable the transplants to grow well. 2.11
Root pruning
This is the cutting back of the actively growing roots of the transplants. Root pruning is carried out so as: to avoid the roots of the seedlings inter-twining, to enable the transplants to develop a well-established root system fit for easy establishment in the field and for the transplants not 51
to penetrate into the soil and get established within the nursery site. Procedure for root pruning About 2 months after pricking out (depending on tree species), root pruning should be done using a panga, knife or pruning saw, When using a knife, the pot is held in an upright position and the roots cut horizontally as shown Fig. 2.2.4a. Alternatively, when using a pruning wire or panga, there is no need of lifting the seedlings off the ground. The panga or wire is moved horizontally at the soil level across the transplant bed in order to cut the roots Fig. 2.2.4b.
a) b) Figure 2.2. 4: a and b. Root pruning using a knife and pruning saw. Source: NaFORRI 2.12
Hardening off
This is the process of creating hard conditions to the seedlings towards the planting season. Reduce the amount of water 4 weeks before seedlings are planted out. At this stage it is advisable to allow the soil to completely dry out and the plants to wilt for a day. This process should be repeated several times. Hardening off helps prepare plants for the new conditions in the field where water might be limiting. Water plants well the day or night before they are taken from the nursery. This will reduce water stress during transport to the planting site. Note: Additional fertilizers may be applied when the seedlings show signs of weakness. The most common fertilizers are NPK and DAP. It’s important to note that manure from livestock can also be used. However weakness of the seedlings can be caused not only by insufficiency of the nutrients but also by pests and diseases. 2.13
Sorting, Culling and grading
• Sorting is a continuous process of arranging seedlings so that those of about the same age, height, species, and pot size are placed together. • Culling is the removable of diseased deformed and dwarf seedlings from the general stock and discarding them. • Grading involves ranking of seedlings of planting age into those that can be planted and those that should be discarded
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2.14
Seedling protection/control
Seedlings are delicate and susceptible to attack by various pests and diseases as well as weather conditions. Such damages can seriously weaken or kill the seedlings. It is important that damages be dealt with immediately. Damage and disasters in the nursery may be categorized as below. a.
Weather conditions This is damage caused by the adverse weather conditions. We can either regulate watering or shading to comply with prevailing weather conditions.
b.
Human interference This is the stealing and/or intentional damaging of seedlings by human beings. Fencing and security are such options to overcome this.
Table 2.2.1 Symptoms and control measures for common tree nursery pests and diseases. TREE NURSERY DISEASES
SYMPTOMS
CONTROL MEASURES
Damping Off
-- Rotting of the root collar -- Massive death of seedlings
Wilting
-- Dying back of the main shoot -- Separating the seedlings or of a seedling immediate planting out.
Powdery mildew
-- Small white powdery patches -are formed on the leaf surface and later the whole surface of the leaf is covered with white powdery mycelial colonies.
-- Use of optimum sowing density to avoid congestion -- Use of appropriate quantity of water, -- Avoid dampness in young seedlings -- Not damaging the bark of seedlings.
Fallen diseased leaves should be buried in soil or burned and the young seedlings sprayed with Benla.
TREE NURSERY PESTS Livestock and wild animals
-- Browse or graze on seedlings.
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-- – Fencing off the Tree Nursery.
Rodents
-- Field mice /rats frequently -cause serious damage to seedlings. TREE NURSERY SYMPTOMS DISEASES Insects -- – Termites are the most -common insects in the nursery. They eat the roots and stems of many tree species. -- – Eucalyptus is particularly susceptible to termite attack.
Cleaning the nursery helps to reduce their population. CONTROL MEASURES
Putting a thin layer of ash (2-3 cm thickness) on the bed, where the pots or tubes of seedlings will be placed. However periodic application is required since ash cannot be effective for long. -- Digging out the queen from nearby colonies (termite hills) or use of plant extracts and chemicals in severe cases. -- Using chemicals e.g Dieldrin & Aldrin
2.15
Nursery records
Keeping records helps to improve the nursery performance. Records on the production costs and productivity of the nursery should be kept so as to to improve planning and operations in the future. Records about the seed source, and destinations, seed performance nursery stock should be kept. In order to have an effective nursery management you have to keep up-to-date nursery records. These are known as; Seedbed register, Transplant bed register and Nursery registers. a. In a seedbed register, you have to maintain seedbed labels; on one side you have species name, on the reverse side, quantity sown, date sown, date of first and last germination. b. In the transplant bed register, you have to maintain seedbed labels as well. On one side you have the Species name, on the reverse side you have the number of seedlings transplanted, date when transplanting started and ended. c. In the nursery register, you have to quote the date when the seeds were received, species received, provenance, quantity in kilograms and some remarks or comments. d. It is advisable to plan nursery activities well in advance of the operations. Organize all activities as per time schedules and monitor the progress of these activities and make accurate records of all the activities. e. Skilled workers need to be available for different activities as need may be. You should know whether to pay workers for work done or to employ them on a permanent basis. 2.16 NURSERY CALENDAR This is very important in planning nursery activities. It shows when different activities are 54
scheduled to be done. Nursery activities are planned backwards from the planting time as this is the dead line for nursery work (Table 2.2.2). Table 2.2. 2. Nursery calendar Activities Jan Feb Mar Apr May Jun Jul Soil collection Soil mixing Pot filling Sowing Pricking out Transplanting Watering Weeding Root pruning Hardening off Planting 2.17
Aug Sept Oct Nov Dec
Vegetative propagation
Vegetative propagation is the growing of plants from cuttings or other non-seed materials such as roots, bulbs and suckers. The cuttings can be obtained from stems, leaves and branches. Some advantages of vegetative propagation are: a. To get trees with desired qualities quickly b. To get trees to mature and fruit quickly. Some of the Different methods used in vegetative propagation include; Grafting, Budding, cutting layering and tissue culture Terms used in grafting and budding i. Scion: The aerial part of a tree that will form the crown of the new plant. This part contains the dormant buds of the tree whose desired characteristics need to be multiplied. ii. Rootstock: The below-ground or lower part of a tree, sometimes including part of the stem and some branches that will form the root system of the new plant. This part may also contain dormant buds which should not be allowed to develop in the new plant since they do not have the desired characteristics that need to be multiplied. Importance of grafting / budding i. To multiply a tree that cannot be multiplied through sexual or other asexual propagation methods. ii. To obtain a tree that combines both the good characteristics of one tree and the rootstock of another one iii. To decrease the amount of time that a tree needs to attain maturity (flowering, seeding) iv. To rejuvenate older trees through the use of young, improved material from another tree. 55
v. vi.
To repair damage caused to certain parts of a tree. To detect viral diseases.
2.18
Grafting
This involves joining a piece of stem of a bud (scion) to another plant (the rootstock) of the same species. There are several types of grafting but most commonly used is cleft grafting. How to do cleft grafting a. Select a desired mother tree. Cut a scion of approximately pencil size in diameter and about 20 cm long. Remove all the leaves carefully. b. Select a rootstock of about the same size as the scion. Cut off the top of the rootstock about 30cm above the soil. c. With a very sharp knife cut the bottom of the scion with two sloping cuts of about 2 to 3cm long (A). Make one straight cut about 3cm deep in the top of the rootstock (B) to form a wedge. The longer the scion the longer the wedge. d. Push the scions firmly into the rootstock cut. Leave ½cm of the cut scions outside the rootstock as shown. e. Use clear plastic tape to wrap firmly around the graft. Do not remove the tape until the scion begins to grow, thus indicating that the graft has been successful. f. Put the graft in the humid chamber to encourage rapid healing and formation of new leaves. Water the plant properly and regularly to prevent drying of the scion tissue. g. Remove any buds which have grown below the graft. If the graft dies, you must allow one bud to grow below the graft and wait several months before trying again (Fig. 2.2.5).
h. Figure 2.2. 5: Top cleft grafting Source: NaFORRI 2.19
Budding
This involves inserting of a strip of bark with bud from the branch of the desired clones to the stem of the seedling stocks. Budding is a form of grafting and is based on the same principles of and requirements for successful union in grafting. There are different techniques that can be used depending on bark slipping or the condition which determines the ease or difficulty of separating the bud from the wood. Similar to grafting, it is important to use vigorous and disease-free rootstocks and scions. There are two com56
monly used Budding techniques in tree propagation. These are T and patch budding. We shall only concentrate on T-budding. Steps in T-Budding a. Wipe the base of the seedling stock with 75 per cent ethanol b. Cut the shield bud from the bud stick or bud wood at about 2cm below the bud with a sharp blade c. Make a vertical cut through the bark of the seedling rootstock at about 3 to 4 cm along a point 3-8 cm above the ground. d. Make a horizontal cut of about 2cm in length across the top of the vertical cut e. Gently spread the bark from the wood properly to make it ready to receive a bud f. Gently push the shield bud into place beneath the bark flaps to make it ready for wrapping g. Wrap the incisions with plastic tape using 0.2mm budding tape with 2cm to 3cm width starting from the lower cut going upward. h. Make sure that the edges of the tape overlap each other. During the first few turning of the wrapping, the lower end of the flap should be kept gently pressed over the bud patch, to prevent it from slipping off. i. Tighten the wrapping to keep the cambium tissues of the seedling stocks and the bud patch in intimate contact with each other. j. Open the tape after 21 days. The budding is successful if the cambium of the seedling stocks and that of the bud patch unite. A green bud patch seen through the tape indicates successful budding. If the patch is black, then it was not successful. k. Cutback (slide cutting) the stem of the budded plants at 3cm to 5 cm from the budded part, three weeks after budding. Apply wax to the wound of the newly cut seedlings. The buds often bear shoots at 7 to 10 days from cutting and are ready for transplanting in the field. 2.20
Cuttings
This is a plant cloning technique where bare plant parts are removed from the parent tree and induced to form roots and shoots which later grow to form new plants. The plant part that is removed is called a cutting. Plants can be propagated from root cuttings, leaf cuttings or stem cuttings. Cutting propagation is often the preferred method for plant propagation because it is the easiest and most cost effective way to produce a clone of a particular parent plant. Stem cuttings from less mature plants, root easily. 2.21
Layering
This is a form of vegetative propagation where cuttings are made to form adventitious roots while the cutting is still attached to the mother plant. Stems of the mother plant are covered in a growing medium in various ways to exclude light, increase the moisture level, and stimulate root growth. Once roots are formed the new plant (layer) is detached and either potted or can be transplanted to the desired location. Types of Layering Simple Layering: A type of layering where shoots from the previous year are bent to the ground (sometimes girdled) and covered in soil and “pegged down” 6-9 inches from the tip. Shoot tips 57
are left emerging from the soil forming a U shape. Shoots are held in place using stakes (Fig. 2.2.6)
Figure 2.2. 6: Simple layer with stake holding shoot in place. Source: NaFORRI Compound Layering: This is a type of layering in which entire horizontal shoots are covered in media causing the formation of numerous rooted layers per branch rather than just one (Fig. 2.2.7).
Figure 2.2. 7: Compound (serpentine) layering. Source: NaFORRI Just like a compound layering except that individual nodes are covered with media. Generally there is an alternation where every second node is covered. Most effective with plants that yield flexible shoots. Air Layering: Air layering is a technique performed without placing the layered branch or shoot below the soil line of the mother plant (Fig. 2.2.8). The stem is first girdled. Proper girdle is key to causing the accumulation of carbohydrates at the cut. Then, the girdled section is wrapped in media like peat moss that is easy to work with. Adding hormone to the media or directly applying it to the stem is very beneficial. The media is then enclosed in plastic and tied off. Once roots have formed the layer can be removed from the mother and planted.
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Figure 2.2. 8: Sequence of air layering; Girdling, applying hormone, wrapping in media and plastic, and tying off . Source: NaFORRI 2.22
Plant tissue culture
Tissue culture involves the use of small pieces of plant tissue (explants) which are cultured in a nutrient medium under sterile conditions. Using the appropriate growing conditions for each ex-plant type, plants can be induced to rapidly produce new shoots by addition of suitable growth hormones. These plantlets can also be divided, usually at the shoot stage, to produce large numbers of new plantlets. The new plants can then be placed in soil and grown in the normal manner. Tissue culture techniques are often used for commercial production of plants as well as for plant research. 2.23
Wildings
A wildling is a seedling that regenerates naturally from dispersed seed. Wildlings can easily be collected and replanted during the rainy season. The wildlings of desired species can be collected while they are still young and transplanted to the farm where they can be protected. They should be carefully uprooted, leaving some soil around the roots, and planted in the same way as seedlings taken from a nursery. The current year’s wildlings are recommended for transplanting because they survive better than older ones. Some examples of trees that can be propagated through collection of wildlings are: Psidium guajava (guava), Mangifera indica (mango), Persea Americana (avocado) etc.
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2.24
Pests and diseases of fruit trees;
Citrus: -- Pests: Orange dog, Leaf minor, White fly, Aphids, Black ants/sooty molds, Scales. -- Diseases: Phaeoramularia leaf and fruit spot., Fusarium wilt, Photopthora root rot, Greening disease, Viruses , Tristeza etc Passion fruit: -- Pests: Mites, Aphids, leaf minors -- Diseases: Collar rot, Brown spot, Viruses, Damping off, Phytopthora Mango: -- Pests: Fruit fly, Aphids, Scales, Mango seed weevil -- Diseases - Mildew, Anthracnose, rust, viruses Avocado: -- Pests: Leaf eating caterpillars, fruit flies -- Diseases: Anthracnose, Phytopthora 2.25
Sourcing tree seed /treatment
It is important to use good quality seed in planting. A poor quality seed will be poor even if it is planted in a well prepared site. Good seed improves survival rate, timber and fruit quality and harvesting period. Seeds can be collected locally from farms, forest or public land. Collect seed from at least more than 30 trees. Seeds can also be bought from suppliers. However, it is important to look at the seed and check that it appears to be of good quality, and hasn’t been collected too early or contains many empty seed when getting it from suppliers. Seed sources (Parent trees) seed should be selected from good parent trees as follows i. From the natural home of the tree species. ii. From where the introduced species is successful. iii. From an area with similar climatic or topographic features. iv. Areas with no signs of pests and disease. Time of seed collection For fruits that open and release seeds when they are dry, collect the seeds just before the seeds are released, a mature seed changes colour, usually from green to brownish. For timber and pole production, consider seed sources with the following features i. ii. iii. iv.
Straight cylindrical stem with a narrow crown. Small branches in relation to stem size. Free from diseases, pests or insect attack Good vigorous growth
2.26
Methods of seed collection
-- Natural seed fall: This usually applies to large seeds. These can be handpicked after fall. Care should be taken to ensure that good mature and healthy seeds are collected. 60
-- From standing trees: In this method, fruits or cones are just picked with hands from the tree branches. Tall trees can be climbed. There is a limit to the height to which long- handled tools can be used for collecting seeds or fruit from the ground. For heights from about 8 to 40 metres, vertical scaling ladders with several sections provide safe and convenient means of climbing the bole to the live crown. The ladders can be made of a variety of materials including wood, aluminum, magnesium alloy, etc., but each section must be light enough to be easily pulled up by the climber. -- After felling trees: This method is applicable for bulk collection from large plantation species where collections can besynchronized with normal commercial harvesting operations. Where phenotypic quality of parent trees is more important than quantity of seed, it is preferable to select, mark, fell and collect the fruit in advance of the main felling. Elite trees with good phenotypes are marked as seed trees before logging. After felling, the seeds are immediately collected from the crowns of the trees. This method is widely used in plantation species in cases where sufficient improved seed is unavailable. Seed availability can be assured by scheduling logging at the time of seeding. 2.27
Seed extraction
After seed collection, seed should be removed from the fruits or cones. This is done as follows: Drying and shaking: This applies to dry dehiscent fruits which burst open when dry; Spread fruits or cones on polythene sheet on the ground; ensure uniform drying by frequent turning of fruits. You can as well put fruits or cones on a raised wire mesh with a tarpaulin below. Don’t spread seed on corrugated iron sheet to avoid overheating. a. Splitting using knives: Used on hard dehiscent fruits like Cassia species, Delonix regia, Jacaranda mimosifolia etc. the fruits are forced open using knives or knockersc) b. Maceration: Used on fleshy fruits which are put in water and smashed, down breaking the pulp. The fruits are then constantly squeezed. The pulp will float and the seeds will settle at the bottom. The fleshy part is then poured off leaving the seeds in the container. Rinse the seeds in clean water and then dry in a cool airy place. c. Biological extraction: Palatable fruits are exposed to animals which eat the fleshy part and leave the seed; care should be taken to ensure that seeds are not eaten too. Cleaning the seeds After seed extraction, seeds should be cleaned to remove the inert part which takes space during storage. It also results in uneven spacing and can attract pests and helps in determining plant yield. Seed storage Seeds collected and extracted that are not going to be used immediately should be stored. Seeds can be stored in airtight containers such as tins, bottles, plastic containers or boxes, which are rodent-free. The containers should be labelled to indicate the species, date of collection, provenance and site of collection. Seeds can be stored in refrigerators at a temperature of about 4-50c. The seeds must be dry (
