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First Virtual Global Conference on Organic Beef Cattle Production September, 02 to October,15 - 2002 — — Via Internet

CROP-LIVESTOCK INTERACTIONS AND SOIL FERTILITY MANAGEMENT IN NORTHWEST NIGERIA Irene Hoffmann Dept. of Livestock Ecology, Justus-Liebig-University Ludwigstr. 21, 35390 Giessen, Germany. Current address Animal Production Service, Animal Production & Health Division – FAO, Viale delle Terme di Caracalla - 00100 Rome, Italy [email protected]

Abstract This study describes an indigenous system of soil fertility management in the Zamfara Forest Reserve, Northwest Nigeria. There, the traditional crop-livestock interaction is being transformed into a more integrated system. Data were collected between 1996 and 2000, combining qualitative and quantitative methods. Methods applied include transect walks, qualitative and semi-structured interviews with farmers and key respondents, and chemical soil analyses with standard methods. Results show that farmers apply a variety of measures to maintain soil fertility. They combine planting patterns with the application of organic manure, using the manure of their own livestock, and by interacting with other groups of livestock owners to manure fields directly.

Keywords :

crop-livestock interaction, crop-livestock integration, farmyard manure, soil fertility, Northwest Nigeria

1

Introduction

Most of the research about crop-livestock integration in West Africa focuses on different bio-physical aspects of nutrient cycling, particularly nutrient balances, and tends to generate average estimates. Less information is available about the socio-economic factors driving farmers’ management strategies. In northern Nigeria, the traditional crop-livestock interaction (McIntire et al., 1992) with exchange relations between separated producer groups and a high degree of livestock mobility is becoming replaced by a more integrated system, where crop and livestock production are found on one farm. Increasing population pressure is one factor driving this transition. As observed in closely settled zones in northern Nigeria (Mortimore et al., 1990), farm size, household size and livestock numbers per household decline as population density and the related land pressure increase. Cropping intensity and labour input increase, and the livestock and crop systems become more integrated. Livestock is more often confined at home than grazing freely. It depends increasingly on labour-intensive cut-and-carry feeding systems of crop residues, grass and browse. Production is oriented towards manure, draught force and milk (Mortimore et al., 1990; Mortimore and Adams, 1998). Small ruminants increase whereas cattle decline. Livestock feeding becomes more labour-intensive because of the scarcity or complete loss of natural Editored by: University of Contestado - UnC - Concordia Unit - Concordia - SC - Brazil Embrapa Pantanal - Corumba - MS - Brazil c

UnC – Concordia – Brazil – 2nd September 2002

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First Virtual Global Conference on Organic Beef Cattle Production September, 02 to October,15 - 2002 — — Via Internet range. Crop residue, cut grass and browse are gathered to feed livestock kept in confinement. Manure production is an important component of livestock production (Harris, 1998). Due to limited resources, smallholder farmers may run into problems of maintaining soil fertility with the manure of their own livestock. Sedentary farmers in north western Nigeria collect manure either from their own livestock or from livestock of transhumant pastoralists. Since the farmers keep only a small number of animals, the quantity of manure is considered insufficient to sustain crop yields and soil fertility. To overcome this problem farmers enter into contracts based on the exchange of manure deposition for crop residue grazing with transhumant herders (Williams et al., 1995; Powell et al., 1996). These traditional socio-economic links between farmers and pastoralists are increasingly disturbed by a reduced mobility of pastoralists and by a loss of pasture due to encroachment of cropland. An increase in the number of livestock kept by farmers has aggravated the competition for available crop residues. There has been much debate about soil fertility in semi-arid West Africa. Until recently a pessimistic view prevailed. Population growth, cropland shortage, decreasing farm size, reduced fallow and soil mining seemed to indicate a bleak future. In contrast to this Mortimore et al. (1990) brought to attention the example of densely populated zones in semi-arid northern Nigeria, such as the Kano Close Settled Zone (KCSZ), that have supported population densities of more than 300 people per km2 for centuries (Mortimore and Adams, 1998; Harris, 1998). The benefits of the use of livestock manure in crop production are improvements in soil physical properties and the provision of N, P, K and other mineral nutrients. The application of livestock manure increases soil organic matter content, and this leads to improved water infiltration and water holding capacity as well as an increased cation exchange capacity. Manure and urine raise the pH level and accelerate the decomposition of organic matter and termite activity (Brouwer and Powell, 1995; 1998). If inorganic fertiliser, especially nitrogen, is combined with manure, the manure reduces soil acidification and improves the nutrient buffering capacity and the release of nutrients (Williams et al., 1995). Farmers’ management is the major determinant of livestock impacts on soil fertility and its spatial and temporal variability. Hence, the present study aims at identifying the farmers’ indigenous strategies to maintain soil fertility. The area chosen is a remote forest reserve where cropland extension is restricted by forestry laws, fields are cropped permanently, and mineral fertiliser is hardly available.

2

Material and methods

The Zamfara Forest Reserve is located between 6o 30’ and 7o 15’E, and 12o 10’ and 13o 05’N in the North of Zamfara State, sharing a border with the Niger Republic to the North, Sokoto State to the West and Runka Reserve of Katsina State to the East. Annual rainfall ranges from 500 mm in the north to 850 mm in the south with considerable inter-annual variations. The vegetation is of a northern Sudan savanna type. The reserve, established in 1918, covers today a total area of 2,300 km2 including four enclave villages (Dumburum, Shamashalle, Tsabre, Aja). About 50 villages are lined up on its western fringe. About 130,000 people live within or around the reserve and utilise its natural resources (ARCA, 1995). The reserve is an important rainy season grazing area for transhumant pastoralists as well as for the herds of the sedentary farmers living in the enclaves or the bordering villages. After the grain harvest, most livestock are fed on stubble. Later in the dry season, transhumant pastoral herds leave the region in search of pasture and water. However, about one third of the Fulani are sedentary and stay in the region with their herds throughout the year (Schaefer, 1998). Despite a low average population density of about 80 per km2 , pressure on cropland is high. Estimates of the actual cropping area per household of about 8 persons (Hassan, 2000; Eckert & Hoffmann, 1998) are between 1.6 and 1.8 ha for Dumburum, Aja, Shamashalle, but 5.4 ha for Tsabre (Hoffmann, 1998). Plot size ranges from 0.2 to 4 ha with an average of 1.1 ha. As arable land is limited, shifting cultivation and fallow are no longer practised, and the fields are under permanent cultivation since 40 years. Bush clearing to enlarge cropping areas is not permitted under the Forestry Law (Forestry Ordinance of 1957), but has always been done to a limited extent. The area is populated by Hausa farmers, and by semi-sedentary, transhumant and nomadic Fulani. Livelihood is based on crop and livestock production. Most large ruminant livestock is kept by Fulani pastoralists. However, the Hausa farmers are increasing their livestock, mainly their small ruminant herds, and also own cattle.

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Figure 1 — Satellite image of the Zamfara Reserve – Landsat 7 ETM RGB 742 – Zamfara Reserve 19 Oct 1999

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First Virtual Global Conference on Organic Beef Cattle Production September, 02 to October,15 - 2002 — — Via Internet The productivity of the rangeland in the reserve is declining due to loss of pasture for cropland encroachment (Hof, 2000) and a shift in the vegetation composition towards less palatable plant species (Kueppers, 1998; Hoffmann et al., 1998). In the enclave villages of the Zamfara Reserve, information on livestock holding (n = 75), crop production, ploughing and weeding (n = 322), crop residue management (n=63) and on each field’s management with respect to number and duration of livestock grazing on stubble (n=57) was collected using structured questionnaires. Informal interviews with farmers provided additional information about their perceptions and strategies. Information on 39 fields with regard to corralling during the dry season and on the number and ownership pattern of livestock and on field size were collected in structured interviews (Gerling, 1998). Complete data were obtained for 7 fields. Livestock data were converted to tropical livestock units (TLU of 250 kg liveweight). The faeces collected as farmyard manure was assumed to be at a rate of 1.1 kg per TLU d-1 when animals are kept in the compound at night. The assumption was made that confined fattening rams produce 2.5 kg faecal DM TLU-1 d-1 (Schlecht et al., 1998). For dung deposition on the fields, it was assumed that animals void 2.2 kg DM when stubble grazing and being night-corralled on the field (Omaliko, 1981; Schlecht et al., 1998), and 0.9 kg DM when manuring the field either at day-time grazing or during night corralling during the progressing dry season (Schlecht et al., 1995; Powell et al., 1996). Following Brouwer and Powell (1995), soil parameters were taken at two characteristic periods of the agricultural year: after nutrient extraction by the harvest in December (1996) and in May (1997), before the onset of the rainy season, prior to field preparation, and following nutrient replenishment by manure application to the fields. Fields were identified by field owners’ names and GPS data. Soil samples were taken randomly from 10 fields in each of the four enclave villages. Twelve to 15 samples per field were obtained from the top 0.2 m and bulked. For comparison, 10 samples were taken from native savanna soil near the four villages. Twenty-one mixed samples of household manure and 9 mixed samples of pure fresh faeces of domestic ruminants were collected from the four villages and the livestock market in Sokoto in September 1997 and September 1998. Dung and soil samples were analysed by standard methods (Hoffmann et al., 2001).

3 Results and discussion Soil fertility management as related to livestock occurred on various spatial levels, involving different natural resources and institutional arrangements: • Using the farmers own resources including his livestock, representing a crop-livestock integration on the farm, • Using livestock of other owners, mainly livestock of pastoralists, representing a regional croplivestock interaction.

3.1

Crop-livestock integration on the farm

The first type of management strategies of farmers relates to the pure crop-related management, the choice of crop species and varieties, and local knowledge about soil types and their inherent fertility. The second type involves the use of the manure of the farmers’ own livestock.

3.1.1

Local knowledge and cropping systems

The land has been continuously cropped for about 40 years, which is quite recent as compared to the Close Settled Zones which are cropped since centuries. Crop rotation is not common. In the vast majority of fields, staple crops such as millet (Pennisetum ssp.) and sorghum (Sorghum bicolor ) were intercropped with the cash generating legumes groundnut (Arachis hypogaea) and cowpea (Vigna unguiculata). Root crops, vegetables and some economic trees are grown to a lesser extent. Rice (Oryza sativa), cotton (Gossypium ssp.) and vegetables are grown on lowland fields. The species and mixtures of crops grown on particular soils depended on how farmers rate the crop production potentials of the soils. The farmers’ choice of the crop varieties depended on the grain and by-product yields. Fifty crop combinations were found. Pure millet cropping was rare (3.4 %), while various two-crop

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First Virtual Global Conference on Organic Beef Cattle Production September, 02 to October,15 - 2002 — — Via Internet combinations, millet plus another crop, occurred most frequently (47.5 %). One quarter of the fields was planted with 3 crops. The most common crop combinations were millet - cowpea, millet - cowpea sorghum, and millet - cowpea - groundnut (Mané-Bielfeldt et al., 1998). The farmers’ soil classification system was based on the texture and colour of the soil, and on the topography. The yield potential of the land was assessed using indicators such as dark soil colour, texture, and a high vegetation density on a flat surface. Sloping lands, especially those directed to the east, or light coloured soils with a high density of grasses were considered as poor farmland. The farmers’ preference for level land might be explained by the higher nutrient leaching on low, wet plots as found by Brouwer and Powell (1998). The major problems mentioned by the farmers were soil fertility and scarcity of organic and inorganic fertilisers. This was mentioned by 75 % of the respondents, erosion in 7 %; 18 % were not aware of any specific problem. Measures used in reclaiming poor soil types included the application of crop residues such as cereal stalks and millet husks to the soil. This reduces the available livestock feed, a loss probably compensated for later due to better water harvesting and soil conservation.

3.1.2

Use of the manure of the farmers’ own livestock

The Hausa farmers in the villages within the reserve kept 6.6 TLU (Table 1), of which 4.4 TLU were kept around their compound. The latter animals are confined in the compound during the night, and dung voided after night rest and drinking in the early morning was collected by the households, as it was recommended by Schlecht et al. (1998). This is also reported by Harris (1998) for the KCSZ. In the evening, the animals were supplemented with crop residues and concentrates such as bran or cereals (Hassan, 2000). About 70 % of the farmers practised small ruminant fattening, mainly of rams, which are kept in permanent confinement for 3 to 7 months. Other farmers confined their livestock during the dry season for better manure collection. The animals produced an estimated 2846 kg of faeces annually.

Table 1 — Livestock holding of farmers in the Zamfara Reserve Zamfara Reserve (n=75) percentage of Mean Median all farmers* TLU 6.6 3.5 -1 TLU ha 3.4 2.1 Cattle (n) 71 7.6 4.0 Sheep (n) 65 13.0 8.0 Goats (n) 67 10.9 7.5 Donkeys (n) 36 1.7 2.0 Dung (kg) 2687 1397 -1 Dung (kg ha ) 1624 885

*

1 cattle = 0.87, 1 donkey =0.5, 1 sheep = 0.1, 1 goat = 0.08 TLU (250 kg liveweight). percentage of those farmers who keep the respective livestock species

In all households waste and animal droppings were swept daily on a heap located at a protected area inside or outside the compound. The farmers ranked the importance of the ingredients of this farmyard manure (takin gida) in the following order: animal faeces > feed left-overs > litter, grass > kitchen residues > ash. They had a clear concept of the quality of the faeces of the different animal species. Cattle dung was the most preferred manure, followed by small ruminant droppings. Donkey droppings ranked last in all cases, because it was believed to cause fungus diseases in millet at the seedling

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First Virtual Global Conference on Organic Beef Cattle Production September, 02 to October,15 - 2002 — — Via Internet stage. According to the farmers, differences exist in the average decomposition time for different animal droppings. Cattle dung completely decomposes within 2.5 years, small ruminant dung and litter after 3.5 years, and donkey dung even more slowly. The farmers explained that the different decomposition time of different types of manure can be used to ensure a continuous flow of nutrients on the field. Their experience is confirmed by Brouwer and Powell (1995; 1998), who found in their experiments a slower decomposition time and less nutrient leaching of sheep manure as compared to cattle manure. The manure heap was left uncovered and untreated in most cases for about 7 months. Only four farmers mentioned adding water to accelerate the decomposition of cereal stalks. The adding of crop residues, litter and ash explains the differences of P and K content between faeces and farmyard manure (Table 3). The N concentration and C:N ratio are in the range given in the literature (Powell and Mohamed-Saleem, 1987; Schlecht et al., 1998). The slightly higher P and K contents compared to literature values (Schleich, 1985; Powell and Mohamed-Saleem, 1987) are probably due to the complete digestion method applied for faeces analysis.

Table 2 — Means of nutrient content of ruminant faeces and takin gida (farmyard manure) in north-west Nigeria Manure type

n

Cattle / small ruminant dung Camel dung Farmyard manure (takin gida)

9 2 21

Nutrient content (%) N P K 1.88 0.95 0.54 1.85 0.93 0.25 0.89 0.24 1.45

At the end of the dry season, the takin gida was transported to the fields and placed in heaps. It was broadcast after the first rains just prior to ploughing. Nitrogen losses might occur at several levels. Firstly, farmers leave the heaps of farmyard manure uncovered in the fields, where N might be lost through volatilisation. Secondly, the manure can be displaced by heavy rains on sloped fields. Although the farmers spread the manure right before ploughing, N might be displaced into deeper soil strata through leaching after the first heavy rains when plant growth is insufficient to absorb the mineralised N (Brouwer and Powell, 1995; 1998). Lastly, the burning of crop residues prior to ploughing leads to N-losses. The average application of all fields in the Zamfara Reserve (7.5 Mg ha-1 , SE 1.03) exceeded that in the KCSZ (4.3 Mg ha-1 , Harris, 1998). An application of 3 to 6 Mg ha-1 was reported to be sufficient to sustain average cereal yields in semi-arid West Africa (Williams et al., 1995). Thus, fields seem relatively well supplied with manure in the Zamfara Reserve.

3.2 Crop-livestock interaction Farmer-herder exchange relations have often been described (Fricke, 1969; van Raay, 1975; Powell, 1986; Powell and Mohammed-Saleem, 1987). All report about an exchange of crop residues against manure, which are the most easily available items for the two groups involved. For the early dry season, Fricke (1969) reported that Fulani manured village or district heads’ fields for free as acknowledgement for good relationships, but that ordinary farmers paid them cereals for manuring beyond one week’s duration. In these studies, however, no clear distinction is made with regard to the season of the exchange and the then resource availability. In the Zamfara Reserve, two types of arrangements occurring at different times could be distinguished. Stubble grazing contracts occur in the early dry season after harvest. Usually the herder pays for access to the crop residue. With regard to nutrient provision, stubble grazing favours an improved nutrient recycling compared to direct application of crop residues (Powell et al., 1996). Under manure contracts, pastoralists night-corral their herd on fields in the late dry season, when no more crop residues are on the field and the surrounding vegetation gets scarce. Animals graze

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First Virtual Global Conference on Organic Beef Cattle Production September, 02 to October,15 - 2002 — — Via Internet and browse the near-by bush during daytime. Hence, corralling of livestock during the late dry season results in a net nutrient transfer from rangeland to the cropland. It also returns dung and urine to the soil, and results in better crop yields than dung alone (Powell et al., 1996). Such nutrient import from the rangeland to the harvested cropland is usually paid for by the farmers. Because the next cropping season approaches, nitrogen losses through volatilisation tend to be negligible as compared to early dry-season manuring.

3.2.1

Stubble grazing

After targeted removal of crop residues for sale or storage, and for own livestock grazing, a farmer can enter into a stubble-grazing contract with a Fulani. Stubble grazing contracts are practised in the Zamfara Reserve, where farmers have crop residues beyond the needs of their own livestock. For farmers who do not own animals, the contracting out of stubble grazing rights is a means to obtain monetary income and manure. The majority of the fields in the Zamfara Reserve (91 %) has been stubble grazed during the early dry season. Only farmers with very small fields did not allow any stubble grazing. On average, 26 cattle and 41 small ruminants grazed the fields for 5.6 days and voided 198 kg ha-1 of faeces (Table 3).

Table 3 — Controlled stubble grazing in the Zamfara Reserve, by herd owners

Field size (ha) Cattle (n) Cattle-days (d) Small ruminants (n) Small ruminant-days (d) TLU (n) TLU-grazing-days ha-1 Dung voided (kg ha-1 )

Fulani (n=9) Mean Median 1.5 0.6 50 40 1.3 1 90 55 1.7 1.5 44 31 66 36 145 78

Hausa families (n=18) Mean Median 0.9 0.5 9 4 8.6 7 22 15 8.4 7 10 5 105 84 232 185

Not indicated (n=21) Mean Median 0.8 0.6 32 7 4.9 2 42 20 4.5 2 30 8 87 54 190 119

Average (n=48) Mean Median 0.9 0.5 26 7 5.6 3 41 20 5.8 3 25 7,4 90 58 198 127

Only data sets with complete information for all parameters were used. Grazing days = number of animals * duration on the field. Of the stubble grazed fields, 19 % were said to be grazed by Fulani herds, 33 % by livestock belonging to Hausa families, either of the own or the extended family, and 47 % of the farmers did not indicate the herd owner. Looking at the average herd size grazing the fields where the farmer did not indicate the ethnicity of the livestock owner, it can be assumed that they belonged mainly to Fulani. While Hausa farmers kept their own livestock for about one week on the field, the larger Fulani herds had finished the crop residues in less than two days (Table 3). Due to the shorter stay of Fulani herds on the fields, less dung is voided on such fields. After controlled removal of all valuable residues, the fields in the Zamfara Reserve are opened for all animals, pastoral herds and village flocks, for uncontrolled grazing during the rest of the dry season. Later in the dry season, transhumant pastoral herds leave the region southwards in search of pasture and water (Schaefer, 1998). The average stocking density on cropland during the dry season was 1.2 TLU ha-1 and resulted in an estimated dung deposition of 200 kg ha-1. This manure application is not spatially controlled (Hoffmann et al., 2001).

3.2.2

Corralling in the late dry season

In the Zamfara Reserve, livestock of the sedentary Fulani find enough grazing on the natural range around the villages - even in the dry season. The number of transhumant Fulani herds declines as the dry season progresses (Schaefer, 1998). Livestock was corralled on 49 % of the fields in the Zamfara Reserve later in the dry season. Fulani and Hausa livestock was corralled on 56 % and 6 % of the fields,

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First Virtual Global Conference on Organic Beef Cattle Production September, 02 to October,15 - 2002 — — Via Internet respectively. For 38 % of the fields the herd owner was not indicated. A large part of these herds might be Fulani owned, since the mean values for this groups did not differ significantly from the Fulani group. An average of 34 TLU ha-1 had been grazing for 43 days on those 7 fields with complete information. The animals provided 1306 kg faeces ha-1 (Table 4). Field size, duration of livestock on the field and the amount of dung voided differed from the same parameters under stubble grazing contracts (p < 0.01). The rotational management of the corrals has been described in Hoffmann et al. (2001). Apart from the regularly shifted night corral, the campsite of the pastoral household was intensively manured by household refuse. Cattle and small ruminant herds of the sedentary Fulani find enough grazing on the natural range around the villages even in the dry season. The number of transhumant Fulani herds declines as the dry season progresses (Schaefer, 1998). Livestock was corralled on 49 % of the fields in the Zamfara Reserve later in the dry season. Some farmers had well established relationships with Fulani families, who come every year to camp on their field. Some farmers mentioned giving cereals to the Fulani, ranging from one bag of millet for one to four weeks of corralling.

Table 4 — Stocking rate and stocking period of nightcorralled livestock in the Zamfara Reserve during the dry season, and faeces voided (n=7) Zamfara Reserve (n=7*) Mean Median 2.79 1.6 33.7 31.5 42.7 45 1306 1380

Field size / farm size (ha) TLU ha-1 Duration of TLU (d) Faeces voided (kg ha-1 ) *

only data sets with complete information for all parameters were used.

It is of interest to note that the fields used for night-corralling (Table 4) were larger than those used for stubble grazing. Obviously only the larger farmers could afford to pay the Fulani for the manure contract, as was also found by Neef (1998) and Mohammed (2000).

4

Conclusion

Although the interview data of this study are variable, the chemical soil analyses shown in table 5 and described in detail in Hoffman et al. (2001) indicate that farmers in the Zamfara Reserve combine crop planting patterns and the application of organic and mineral fertilisers in an effective way to maintain the fertility of their soils. Intensive application of farmyard manure was found to be the most important source of nutrients, followed by dung voided by livestock directly on the field. Nutrient transfer from the rangeland to the cropland through takin gida application or corralled animals is an important factor for maintaining soil fertility. However, productivity of the rangeland in the reserve is declining due to loss of pasture for cropland encroachment and a shift in the vegetation composition towards less palatable plant species. In the medium and long term, this might adversely affect the number and productivity of livestock kept, and the productivity of the cropland supported by nutrient transfer. In the CSZs in northern Nigeria, however, a positive correlation was found between human and livestock population densities, based on an intensive crop - tree - livestock integration. The Zamfara Reserve seems to be on a transition from an extensive, less integrated to an intensive, more integrated crop-livestock system. Farmers use their own and pastoral livestock to manure their fields. Poor farmers cannot engage in manure contracts due to their limited resources. Hence, soil fertility differences between farmers might increase in the long run, aggravating the existing wealth differences.

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Table 5 — Soil fertility parameters in cropland and native savanna in the Zamfara Reserve (December 1996 (after harvest) and May 1997 (after manuring)) -1

Total N (g kg )

Dec. 1996 May 1997 Mean -1 Total C (g kg ) Dec. 1996 May 1997 Mean C/N ratio Dec. 1996 May 1997 Mean -1 P Bray (mg kg ) Dec. 1996 May 1997 Mean -1 Avail. K (mg kg ) Dec. 1996 May 1997 Mean pH in H2 O Dec. 1996 May 1997 Mean

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Cropland 0.35 0.22 0.28 3.4 3.3 0.4 9.79 16.08 12.93 35.5 45.23 40.26 51.04 86.33 68.69 6.41 6.7 6.55

Native savanna 0.35 0.27 0.3 3.6 4.2 3.9 10.74 15.66 13.2 20.2 22.37 21.29 63.75 82.14 72.75 6.23 6.51 6.37


5

Acknowledgements

I am grateful to the DG VIII and DG XII of the European Union for financing the research under the projects ’Range development and camel studies’ (06 ACP UNI-015) and ’Range development in the endangered Sudan Savanna in Sokoto State, Nigeria’ (TS 3-CT 91-0011). I also thank our colleagues from the Usman Danfodiyo University Sokoto and the people in the villages for their co-operation. I acknowledge the support of our colleagues from the Institute of Soil Science for analysing the soil and dung samples.

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References

ARCA, 1995. Forest Reserve study: Ruma Kukar Janjarai and Zamfara Forests. Final report Vol. 1. The environment: present conditions and degradation factors. Katsina Arid Zone Programme, Federal Republic of Nigeria, National Planning Comission. Brouwer, J., Powell, J.M., 1995. Soil aspects of nutrient cycling in a manure experiment in Niger. In: Powell, J.M., Fernandez-Rivera, S., Williams, T.O., Renard, C. (Eds.). Livestock and sustainable nutrient cycling in mixed farming sytsems of sub-Saharan Africa. Vol II: Technical papers. Proc. of an International Conference held in Addis Ababa, Ethiopia, 22.-26. November 1993. ILCA, Addis Ababa, Ethiopia, pp. 211-226 Brouwer, J., Powell, J.M., 1998. Micro-topography, water balance, millet yield and nutrient leaching in a manuring experiment on sandy soil in south-west Niger. In: Renard, G., Neef, A., Becker, K., von Oppen, M. (Eds), Soil fertility management in West African land use systems. Proc. of a workshop held in Niamey, 4.-8 March 1997. Margraf, Weikersheim, pp. 349-360 Eckert, B., Hoffmann, I. 1998. Statutory versus customary land allocation. Implications on land tenure and resource management. In Hoffmann, I. (ed.), Prospects of pastoralism in West Africa. Giessener Beiträge zur Entwicklungsforschung. Reihe I, 25 : 169-178. Fricke, W., 1969. Die Rinderhaltung in Nordnigeria und ihre natur- und sozialräumlichen Grundlagen. Frankfurter Geographische Hefte 46. 252pp. Gerling, D., 1998. Der Einfluβ des Dünger- und Kompostmanagements auf die Bodenfruchtbarkeit in der Sudansavanne. Eine Untersuchung im Zamfara Forstschutzgebiet im Nordwesten Nigerias. Unpubl. M.Sc. thesis, Giessen. Harris, F.M.A., 1998. Farm-level assessment of the nutrient balance in northern Nigeria. Agric. Ecosyst. Environ. 71, 201-214 Hassan, W.A., 2000. Biological productivity of sheep and goats under agro-sylvo-pastoral systems in the Zamfara Reserve in north-western Nigeria. Cuvillier, Goettingen, 260pp Hof, A. 2000. Developing a GIS methodology for the Analysis of agro-pastoral livelihood and ecosystems in the Zamfara Forest Reserve, NW Nigeria. MSc dissertation, Dept. of Geography, University of Durham, September 2000. Hoffmann, I. 1998: Zamfara Reserve - Past and present. In: Hoffmann, I. (Ed.), Prospects of pastoralism in West Africa. Giessener Beiträge zur Entwicklungsforschung, Reihe I, Bd. 25, 1-9. Hoffmann, I., Gerling, D., Kyiogwom, U.B., Mané-Bielfeldt, A., 2001. Farmers’ management strategies to maintain soil fertility in a remote area in Northwest Nigeria. Agric. Ecosyst. Environ. Vol. 86 (3) 263-275. Hoffmann, I., Willeke-Wetstein, C., Schaefer, C., 1998. Desription of a grazing ecosystem in Northwestern Nigeria, using environmental indicators. Anim. Res. Development 48, 69-83 Kueppers, K. 1998. Evaluation of the ligneous strata of the vegetation of the Zamfara Reserve. In: Hoffmann, I. (Ed.), Prospects of pastoralism in West Africa. Giessener Beiträge zur Entwicklungsforschung, Reihe I, Bd. 25, 41-47. Mané-Bielfeldt, A., Schaefer, C., Gefu, J., Hoffmann, I., Mohammed, I., Steinbach, J., 1998. Crop production and utilisation in the Zamfara Reserve. In: Hoffmann, I. (Ed.), Prospects of pastoralism in West Africa. Giessener Beiträge zur Entwicklungsforschung, Reihe I, Vol. 25, pp. 238-246 McIntire, J., Bourzat, D., Pingali, P., 1992. Crop-Livestock Interaction in Sub-Saharan Africa. Washington, D.C. The World Bank. Mohammed, I., 2000. Study of the integration of the dromedary in smallholder crop-livestock production systems in northwestern Nigeria. Cuvillier, Goettingen, 230pp

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First Virtual Global Conference on Organic Beef Cattle Production September, 02 to October,15 - 2002 — — Via Internet Mortimore, M., Adams, W.M., 1998. Farming intensification and its implications for pastoralism in northern Nigeria. In: Hoffmann, I. (Ed.), Prospects of pastoralism in West Africa. Giessener Beiträge zur Entwicklungsforschung, Reihe I, Vol. 25, pp. 262-273 Mortimore, M., Essiet, E.U., Patrick, S., 1990. The nature, rate and effective limits of intensification in the small holder farming system of the Kano Close-Settled Zone. Federal Agricultural Coordinating Unit, Ibadan Neef, A., 1998. Le contrat de parcage, fumure pour les riches? Une étude de cas au sud-ouest du Niger. In: Renard, C., Neef, A., Becker, K., von Oppen, M. (Eds.), Soil fertility management in east African land use systems. Proc. of a workshop held in Niamey, March 4-8, 1997. Margraf, Weikersheim, pp. 381-386. Omaliko, C.P.E., 1981. Dung deposition, breakdown and grazing behaviour of beef cattle at two seasons in a tropical grassland ecosystem. J. Range. Management 34(5), 360-62 Powell, J.M., 1986. Manure for cropping: A case study from central Nigeria. Expl. Agric. 22, 15-24. Powell, J.M., Fernandez-Rivera, S., Hiernaux, P., Turner, M.D., 1996. Nutrient cycling in integrated rangeland/cropland systems of the Sahel. Agric. Syst. 52 (2/3), 143-170 Powell, J.M., Mohamed-Saleem, M.A., 1987. Nitrogen and Phosphorous transfers in a crop-livestock system in West Africa. Agric. Syst. 25, 261-277 Schaefer, C., 1998. Pastorale Wiederkäuerhaltung in der Sudansavanne: Eine Untersuchung im Zamfara Forstschutzgebiet im Nordwesten Nigerias. Cuveillir, Goettingen, 217pp Schlecht, E., Fernandez Rivera, S., Hiernaux, P., 1998. Timing, size and nitrogen concentration of faecal and urinary excretions in cattle, sheep and goats: Can they be exploited for better manuring of cropland? In: Renard, C., Neef, A., Becker, K., von Oppen, M. (Eds.), Soil fertility management in West African land use systems. Proc. of a workshop held in Niamey, 4.-8. March 1997. Margraf, Weikersheim, pp. 361-368 Schlecht, E., Mahler, F., Sangaré, M., Susenbeth, A., Becker, K., 1995. Qualitative and quantitative estimation of nutrient intake and faecal excretion of zebu cattle grazing natural pasture in semi-arid Mali. In: Powell, J.M., Fernandez-Rivera, S., Williams, T.O., Renard, C. (Eds.), Livestock and sustainable nutrient cycling in mixed farming systems of sub-Saharan Africa. Vol II: Technical papers. Proc. of an International Conference held in Addis Ababa, Ethiopia, 22.-26. November 1993. ILCA, Addis Ababa, Ethiopia, pp. 85-98 Schleich, K., 1985. Ansätze zur Integration von Ackerbau und Viehhaltung in der Savanne Westafrikas. Materialien 10. Zentrum für regionale Entwicklungsforschung der Justus-Liebig-Universität Giessen. SPSS, 1999. Statistical package for social sciences, version 9.01 German Van Raay, H.G.T., 1975. Rural planning in a savanna region. University Press, Rotterdam Williams, T.O., Powell, J.M., Fernandez-Rivera, S., 1995. Manure availability in relation to sustainable food crop production in semi-arid West Africa: Evidence from Niger. Quarterly J. Internat. Agric. 34 (3), 248-258.

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