Germany. Keywords: apple, climate change, global warming, ground cover; mechanisation, ... public universities as well as commercial companies. This is to .... New harvesting technology under development at OxBo, USA includes on-site.
Managing Open Field Production of Perennial Horticultural Crops with Technological Innovations Michael M. Blanke INRES- Horticultural Science University of Bonn Auf dem Hüegel 6 D-53121 Bonn Germany Keywords: apple, climate change, global warming, ground cover; mechanisation, reflective ground cover; resource conservation, sustainable horticulture, sunburn Abstract Technological innovations appear under-utilised in many fruit tree crops, whereas viticulture, citriculture and vegetable crops have largely automated planting, pruning, thinning and harvesting and integrated GPS and/or GIS in their cultivation practises. As a consequence of the trend from pedestrian to tall orchards, innovation and technology is required to overcome shading, particularly in the lower part of the tree canopy. Types, properties and prices are presented of reflective ground covers (textile, aluminium and paper) as well as organic alternatives (lime, straw) as well as titanium dioxide and bio-degradable white line marker paint with additives. To combat sunburn, kaolin, carnauba-wax and other products are available, which can be combined with evaporative cooling. Mechanisation includes new machinery for mechanical thinning, pruning and harvesting to save labour. An autonomous prime mover (APM) is being developed for camera systems for assessment of flowering intensity, alternate bearing, fruit set, June drop, leaf nutrient status, pest and disease control and yield estimation/prediction. The two approaches for better light utilisation in row systems include reducing the spacing of every row from the current 14 feet (4.3 m) to 10–12 feet (3.0 to 2.6 m) or maintaining the spacing of a centre row at 14 feet (4.3 m) or ease of access, but narrower row spacing either side to less than 10 feet (3.0 m) The OTR (over the tree rows) developed by Washington State University and two commercial European multi-row sprayers are presented and new harvesting techniques with pre-sorting in the orchard. INTRODUCTION Technological innovations appear under-utilised in many fruit tree crops, whereas viticulture, citriculture and vegetable crops have largely automated planting, pruning, thinning and harvesting and integrated GPS and/or GIS in their cultivation practises. Hence, the objective of this colloquium 06 was to present technologies under development in research for the cultivation of fruit crops in the field from both from public universities as well as commercial companies. This is to provide an overview of innovations and emerging technologies to encourage discussion on future developments and their implications for fruit growers.
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GROUND COVERS TO OVERCOME LIGHT DEFICIENCY UNDER ENVIRONMENTAL NETS AND PLATFORMS FOR USE WITH TALLER TREES Many fruit growing regions face a trend from the pedestrian orchard with slender spindle to the tall spindle training of apple and other fruit trees: The underlying principle is improved utilisation of the present tree row system, where a portion of incident sunlight is lost in the alleyways; this approach aims at a larger tonnage per incident radiation or per acre. Shading particularly of the lower part of the tree canopy is an undesired consequence, and an open scaffold and summer pruning as possible cures. This shading is accelerated in fruit growing regions, where environmental nets for bird and hail protection or shade control are employed. Reflective ground covers are one of the innovations of the last ten years to overcome shading in form of white woven materials such as ExtendayR, DaybrightTM (Extenday), TS GroundcoverTM (Svensson) or BrighterWhiteTM, industrial papers such as Uniset OTM (Stora Enso) or silver aluminium–based films such as ‘Brite N up’ (MylarTM). Their initial investment costs range from €0.06/m2 with the industrial paper to €0.50/m2 with ExtendayR depending on material and life-span. This amounts to up to €5,000/ha (Extenday) investment cost, which will be spread over their life-span of 8–10 years. Research and development has come up with a wide choice of different synthetic materials for ground covers now (Meinhold et al., 2010) providing individual solutions for each region and purpose (Fig. 1). The alternatives are lime or white bio-degradable paint, the latter used as line marker in sports grounds, on the grassed alleyways (Blanke, 2007); research started in autumn 2010 on new formulations of titanium dioxide with certain additives for the same purpose for use on the grass alleyways. Two approaches consist of spreading the ground covers for improvement of (red) top colour in bi-coloured apple cultivars 3–4 weeks (high light in med climates), 4–5 weeks (medium light at 50°N) and 5–6 weeks (low light environments >53°N) (Solomakhin and Blanke, 2007), or spreading the ground cover from after bloom in May to enhance cell division and flower induction for the following year.
Fig. 1. Experiments with “reflectors” such as lime, bio-degradable paint and straw (left) as well as Extenday and Mylar to reflect light from the alleyways into the bottom of the tree canopy in Klein-Altendorf at the University of Bonn, Germany (right).
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Larger, taller fruit trees also require work lifts or platforms for all orchard operations from pruning, training, hand-thinning, and harvesting at a cost of up to €30,000 per vehicle depending on its versatility, a cost which has to be recovered from the additional income of the taller versus the slender tree. COMBATING SUNBURN Climate change increases the risk of sunburn (Blanke and Kunz, 2009). e.g. in the med and Washington State fruit growing region. Three types of sunburn have been distinguished and can occur at fruit temperatures above 45°–52°C. Table 1 lists only 3 out of the ca. 10 products currently available; some have not been sufficiently tested for a final judgement. Kaolin (Surround®) reflects light irrespective of wavelength (Fig. 2), but may result in less top colour making it more suitable for single-coloured green varieties or early application, and, under temperate climates smaller fruit due to its reflective properties. Raynox® is based on carnauba wax, extracted from palm trees, which selectively filters out UV radiation and is also now used in human sunscreen (Schrader, 2010). Both compounds can be combined with low volume overhead sprinklers, which reduce the fruit surface temperature from 40°C to 34°C (Schrader, 2010). MECHANISATION FOR AUTOMATION-MECHANICAL PRUNING Technology is increasingly becoming available for both top and stone fruit tree crops for mechanical pruning, i.e. hedging, i.e. pruning the sides of the tree row, and topping, i.e. pruning the tops (Fig. 3). First results indicate that each side has to be pruning in alternating years. Mechanical pruning is to partially or completely substitute manual pruning using pneumatic or electric shears. Table 1. Technologies available as effective countermeasures against sunburn. Method Ingredient Color Mode of action Application rate Surround® Kaolin White Reflects light Spray 2–3× Raynox® Carnauba wax Transparent Filters out UV light Spray 2–3× Overhead low Water Evaporative cooling Every 8–10 min. vol. sprinklersz when required z Can be combined with thinning compound
Fig. 2. Use of kaolin (Surround®) on the tree to overcome sunburn on apple fruit combined with overhead sprinklers.
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FROST PROTECTION Where wind machines are not acceptable from a countryside view or water for overhead irrigation for frost protection not available, the Belgian company LAZO offers an alternative (Fig. 4). The stationary or tractor-pulled ‘Frostbuster’ burns gas to blow 90°–100°C air into the orchard. Efficacy obviously depends on many factors like temperature and wind. Further research is necessary to identify the conditions the frost buster can effectively protect our fruit crops. BREEDING FOR SELF-THINNING CULTIVARS VERSUS MECHANICAL THINNING Fruit trees are generally not capable of maintaining their fruit load from flowering to harvest (Untiedt and Blanke, 2001). So far, breeding for ‘self-thinning varieties’ has not resulted in new varieties without the need of thinning. The “self-thinning” idea was based on “singlets,” i.e. one fruitlet per cluster, and was to be achieved e.g. by a severe post-
Fig. 3. Device for mechanical tree pruning: hedging (left); and cherry trees (right) after topping
Fig. 4. The two models of the LAZO ‘Frostbuster’ looks like an oversized hair blower and is being developed in Belgium. The tractor pulled version (left), which covers ca. 10 ha and has to be driven through the orchard all night every second row as long as the frost risk remains and a stationary version for a smaller acreage (right).
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bloom and/or June drop, but suffered from interference from environmental conditions and their variable effects on flower and June drop. By contrast, many new varieties including “club varieties” including ‘Pinova’, ‘Honeycrisp’ require a large amount of thinning to achieve the high fruit size and colouration standards of the club and climate change has not waived this need (Blanke and Kunz, 2009a,b). Four approaches can be used for thinning: breeding, chemical thinning, mechanical and hand-thinning. Another wide, so far under-utilized choice of technologies becomes available for horticulture viz for tree fruit thinning. Many fruit growing regions face a trend from the slender spindle to the tall spindle training and fruit walls of apple and other fruit trees, which enables the choice of both mechanical pruning and mechanical thinning. The next challenge is for the nurseries and fruit grower to train the fruit trees in a way suitable to both mechanical thinning and pruning. Two tractor mounted devices are suitable for all types of spindle trees, whereas Vshape or older, larger trees with inaccessible branches can be treated with the hand-held, e.g. battery-driven device (Table 2, Fig. 5). In case of severe alternate (biennial) bearing, Table 2. Mechanical thinning devices currently available. Device Power Source Darwin 2000 TractorGessler/Fa. mounted: FruiTec, front 3 Germany point hitch The Bonner TractorUniversity (UniBonn) mounted: of Bonn, front 3 Germany point hitch Effleureuse Hand-held Electroflor, France
Selective Tractor Design thinning speed Vertical mast, No 5–10 1 vertical km/h rotor Vertical mast, 3–4 horizontal rotors
Yes
Yes
4–8 km/h
Price (€000) 6–7
7–8
3–4
Fig 5. Three mechanical thinning devices are commercially available, two for front hitch tractor mounting (left, courtesy of M. Meland) or hand-held use (right; Electroflor).
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mechanical thinning can be applied at the pink bud stage (BBCH 57; E1), which is then associated with larger yield loss. In most cases, mechanical flower thinning is between the balloon stage (BBCH 59; E 2) until after full bloom (BBCH 67) at tractor speeds of 4–8 km/h (Solomakhin and Blanke, 2010). In fire blight sensitive areas or conditions, mechanical thinning during late flowering is to be followed by a streptomycin application or similar compound to avoid any infection (Ngugi and Schupp, 2009). OTRS FOR ALL CULTIVATION PRACTISES, MULTI-ROW SPRAYERS, PLATFORMS AND HARVESTING TECHNIQUES The underlying principle is improved light utilisation of the present tree row system, where a considerable portion of incident sunlight is lost in the alleyways; this approach aims at larger tonnage per incident radiation or per acre by reducing row spacing (rather than tree to tree spacing). Two approaches exist: (1) Washington State University developed a new technology. The self-propelled OTR provides the over the tree row and covers ca. 5 tree rows and is flexible in that any device could be suspended from a frame including mechanical thinning, pruning, spraying or harvesting equipment (Fig. 6). (2) The alternative approach is dedicated machinery for individual purposes: Two companies have developed multi-row, mostly 3 row, sprayers, for flexible, adjustable row spacing. Both approaches can be regarded as old-fashioned or traditional, as long as we use the existing row spacing, but aimed at new strategies. These could include one row with standard width viz row spacing (e.g. 12 feet, 3.6 m) but more narrow spacing either side (e.g. 8–10 feet, 2.4–3.0 m). A wide range of platforms are now becoming available, some of which incorporate spaces for in the orchard sorting of refuse fruit (culls) (Fig. 7). MECHANISATION OF FRUIT HARVEST New harvesting technology under development at OxBo, USA includes on-site fruit sorting to exclude culls (Fig. 7, 8). The Belgian company ARCO develops robots for automated fruit picking. The robotic arm contains a camera system, which detects and recognises the red apple fruit against a dark background and sucks in the fruit into a flexible hose, like a vacuumcleaner, which end in a bin with the fruit stalk (pedicel) being mostly retained on the fruit (Fig. 9).
Fig. 6. Self-propelled OTR (over the tree row) developed by Washington State University (left), devices can be suspended from the frame for spraying, pruning, thinning or harvesting; and multi-row (or over the tree OTR) spraying equipment.
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AUTONOMOUS PRIME MOVERS (APM) FOR DATA ACQUISITION Carnegie Mellon in collaboration with Vision Robotics currently develop an autonomous prime mover (APM), which is being tested in combination with camera systems for assessment of flowering intensity, alternate bearing, fruit set June drop, leaf
Fig. 7. Developments towards mechanical harvesting of fruit under development by OxBo, WA.
Fig. 8. Mechanical assist prototype apple harvester, developed by Oxbo, provides vacuum to suck the manually-picked fruit into the bin.
Fig. 9. The ARCO robot developed in Belgium for (apple) fruit picking; the white hose end contains a camera systems, which recognizes potential fruit on the tree against a dark background.
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nutrient status, pest and disease control and yield estimation /prediction and is described in a parallel paper (Kantor, 2011, this volume of Acta). CONCLUSIONS New emerging technologies for use in horticultural field crops include: 1. A wide range of countermeasures to overcome shading in the lower part of the canopy of tall trees viz orchards is emerging from woven textiles and aluminium foil to paper as reflective ground covers, lime, straw, titanium dioxide and bio-degradable white paint for use on the grass of the alleyways. 2. A range of countermeasures against sunburn from kaolin based to carnaubabased compounds and/or low volume overhead sprinklers for evaporative cooling. 3. A whole range of different platforms, which became available over the last 3 years, to accommodate the change from pedestrian to tall spindle orchards. 4. Mechanical pruning–hedging and toping devices becoming available. 5. Mechanical thinning with two tractor mounted and two hand-held devices commercially available since 2010. 6. Autonomous vehicles (APM – autonomous prime mover) being tested in combination with camera systems for assessment of flowering intensity, alternate bearing, fruit set June drop, leaf nutrient status, pest and disease control and yield estimation /prediction. 7. New harvesting technology includes on-site fruit sorting to exclude culls. 8. Robots being developed for automated fruit picking. ACKNOWLEDGEMENTS I’m grateful Jim McFerson for organising the colloquium and revising the manuscript and to Referat 521 of DAAD/DFG/Auswärtiges Amt Bonn for the travel grant to the International Horticultural Congress (IHC 2010) in Lisbon in August 2010 to present these results. Literature Cited Blanke, M. and Kunz, A. 2009a. Misconceptions about the effects of climate change on horticulture. Proc. Benelux Horticultural Society Annual Meeting 3 April 2009, Gembloux, Belgium, Ed. Monique Bodson, p. 12. www.beneluxshs.eu/index.html Blanke, M.M. and Kunz, A. 2009b. Effects of climate change on pome fruit phenology at Klein-Altendof [Auswirkungen rezenter Klimaveränderungen auf die Phänologie von Kernobst am Standort Klein-Altendorf]. Erwerbs-Obstbau (Springer, Heidelberg) 51(3):101–114 (special edition on climate change). Blanke, M.M. 2009. Managing fruit loads and harvesting tree fruit: Challenges for the future from a European perspective. Proc. 104th Ann Meeting WSHA, Yakima, Washington State, USA, 3 December 2008 (Smith, L., ed.), WSHA Publ., Yakima, p. 51–62. Kantor. 2011. Distributed sensing in horticultural environments. Acta Hort. x:x–x. Meinhold, T, Damerow, L. and Blanke, M. 2011. Reflective materials under hailnet improve orchard light utilisation, fruit quality and particularly fruit colouration. Scientia Hort. 127:147–151. Ngugi, H.K. and Schupp, J.R. 2009. Evaluation of the risk of fire light in apple orchards with a mechanical string blossom thinner. HortScience 44:862–865.
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Solomakhin, A. and Blanke, M. 2007. Overcoming adverse effects of hailnets on fruit quality and microclimate in an apple orchard. J. Sci. Food Agr. 87:2626–2636. Solomakhin, A. and Blanke, M. 2010. Mechanical flower thinning improves fruit quality of apples. J. Science Food Agr. (SCI London) 90(5):735–743. Schrader, L. 2011. Scientific basis for a unique formulation for reducing sunburn of fruits. HortScience 46:6–11. Untiedt, R. and Blanke, M. 2001. Effects of fruit thinning agents on apple tree canopy photosynthesis and dark respiration. Plant Growth Regulation 35:1–9.
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