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Organic Stone-Fruit Production: Optimizing Water Use, Fertility, Pest Management, Fruit Quality and Economics


The goals of this project are to: 1) develop a long-term on-farm research site devoted to testing and showcasing organic stone-fruit management strategies for increased water use efficiency, soil quality, pest management, fruit quality and economic stability in climates characterized by arid summers and cold winters; 2) develop a county Extension personnel trained in organic production methods; 3) work with Extension Agents, growers, fruit industry personnel, and national park officials to improve quality of life of rural populations by enhancing access to environmentally friendly, locally produced and nutritious foods while maintaining productive farmland through increased farm profitability and reduction of pesticide use. <P>We will work towards these goals through the following specific objectives: A. Characterize potential tradeoffs in water use efficiency and tree growth with living and non-living mulches, internal and external fertility inputs, and soil quality. B. Characterize weed and arthropod response to organic management practices. C. Select orchard floor cover crops for optimizing weed suppression, arthropod dynamics, water use, and early season N release for cold winters, arid summers and shallow alkaline soils. D. Select orchard floor management for maximum fruit quality, environmental benefit and economic return. F. Increase adoption of stone-fruit organic production through education and outreach.

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Non-Technical Summary: Fruit production in Utah and throughout the Intermountain West has come under increasing pressure in recent years due to: rising input costs, diminishing water supplies, and urban encroachment. Growers are seeking new management and marketing opportunities to withstand these pressures. While Utah has several regions historically noted for high quality fruit production, there are currently no organic stone-fruit growers in the state. Pressures from pests such as western cherry fruit fly and weeds kept growers in the area skeptical about transitioning to organic management. With conventional growers successfully implementing attract-and-kill and reduced-risk insecticides such as spinosyns, interest in organic management has grown. Managing weeds and fertility now appear to be the greatest challenges to organic production. As irrigation water is already a limiting factor, sustainable orchard floor management will need to optimize water use. We are proposing to carry out a long-term on-farm replicated trial of organic peach management systems, along with several companion orchard floor trials, and evaluate these for weeds, insects, fertility, water use, fruit quality, and economic potential. The goal is to compare management systems for suitability to arid climates with cold winters and shallow alkaline soils, to quantify the benefits and/or tradeoffs of these systems, to demonstrate these strategies to growers, and to train crop consultants, extension professionals and students in regionally appropriate organic practices. Results from these research and outreach efforts will enable local experts to better advise growers on organic fruit management strategies and lead to adoption of organic stone-fruit production in the region. <P> Approach: Two orchards were established in April of 2008 at the USU Horticulture Research Station in Kaysville UT. The organic site was planted in a randomized complete block design with 4 blocks and 6 treatments. The six treatments are 1) straw mulch with a grass alleyway 2) straw mulch and a legume alleyway 3) living mulch (low-growing shallow rooted allysum) with grass alleyway 4) living mulch and legume alleyway 5) woven plastic mulch with a grass alleyway 6) tillage and high compost with grass alleyway. The conventional orchard is located next to the certified organic orchard on the same soil type and planted as described above. Three treatments include: 1) conventional herbicide + NPK as an industry standard, 2) conventional herbicide + NPK to be converted to organic after tree establishment and, 3) organic from planting, compost + spray on paper mulch. Tree leaf N and nutritional status will be assessed every year and these results used to determine fertilization rates. Percent increase in tree cross sectional area will be measured yearly. Soil nitrogen status will be determined at monthly intervals from May through August. Macro and micro elements will be measured yearly. Each experimental plot is equipped with an individually controlled micro sprinkler irrigation system. Flow meters in the system also allow for precisely determining water inputs. In order to assess soil quality differences between treatments, soil will be sampled in May during the course of the study. Each plot will be visually surveyed and all weed species in the plots recorded regardless of the number of plants present. Weed response to mulch and alleyway treatments will be evaluated by measuring weed densities within each treatment. Each type of arthropod sample will be collected to correspond to key tree phenology stages: 1) bloom (late April - early May), 2) shuck-split (early June), 3) pit-hardening (late June - early July), 4) rapid fruit enlargement (late July - early August), 5) harvest (late August - early September), and 6) post-harvest (late September).Novel cover crops will be assessed for suitability in orchards under Utah conditions in a separate trial. Establishment, weeds and arthropods will be monitored as described above. Fruit quality will be measured in year three and four of the study on the second and third expected crop. Sensory evaluation at the USU Food Science sensory evaluation laboratory will be conducted with 15 trained panelists1 All input costs will be tracked for each treatment. A sample of fruit from each treatment will be freeze dried for fruit chemistry analysis using HPLC. Cost benefits analysis will be conducted for each management scenario in the orchard trials using partial budgets. Capital budgeting techniques will be used to allow multiple years of the growing cycle to be taken into account. Each of the participating growers will test one, two or three of the above management plans in their own orchards depending on interest and available trees for the experiment. They will select the plan most suited to their operation, available equipment, interests, and needs, and modify it as needed.

Reeve, Jennifer
Utah State University
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