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Jason McAfee and Curt Rom

Pesticides and alternative fruit thinners are needed for certified organic fruit growers. Transient reductions in photosynthesis (Pn) have proven an effective technique for fruit thinning. Pesticides can be detrimental to plant growth by Pn reduction. This study was developed to measure plant response to foliar applications of essential oils at 2% concentrations. Treatments were applied to vegetative apple trees grown under controlled environment conditions to study photosynthetic effects. There was no significant effect on Pn for treatments; however, clove oil was very phytotoxic and defoliated all trees in this study. Cinnamon oil and cedarwood oil significantly decreased evapotranspiration and stomotal conductance 1 day after treatment. Differences in plant growth were not significantly different for all treatments excluding clove oil. Studies on concentration effects may determine horticultural usefulness of these compounds.

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Curt R. Rom and Jason McAfee*

`Apache' blackberry planted in 3-m plots spaced at 0.6 m between plants were maintained either with or without waste municipal wood chip mulch and grown for 5 years. Plots received similar weed control, pest management, and irrigation. All plots were annually hedged at 1.35-m height twice during midsummer to encourage branching. Fruit were harvested beginning in the second season after a season of establishment. Annual yield in the mulched plots was 15% greater, average fruit size was 4% larger, and cumulative yield was 9% greater in the mulched plots compared to nonmulched control plots. In two seasons, average berry soluble solids content of fruit from mulched plots was slightly, but not significantly higher. Annual primocane number was 33% greater, floricane number 41% greater, floricane dry weight after harvest was 15% greater, and average plant height before summer pruning was 24% taller in mulched plots compared to nonmulched plots. Mulch significantly reduced weeds within the plots.

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Hyun-Sug Choi, Curt Rom, and Jason McAfee

Mulch may affect soil chemistry, soil microclimate, biological communities, and tree performance. The trial was conducted to evaluate the effects of different orchard mulches on leaf nutrition, soil moisture, bulk density, root density, and water infiltration for understanding potential use in organic orchards for weed control and as a nutrient resource. Black plastic, hardwood chips, and shredded white paper were applied to three apple cultivars, `Gala', `Jonagold', and `Braeburn' on M.9 rootstocks. A control was sprayed with contact herbicide. Trees grown in hardwood mulch had the highest foliar P and K in year 3. Trees in other mulches showed no difference of leaf nutrition in year 5. All treatments had consistently higher soil moisture than control in year 1, 2, and 4. Mulch did not affect soil bulk density in year 2. The root density was lowest under black plastic mulch in year 2, but was similar in all treatments in year 3. In year 2, water infiltration was fastest in hardwood mulch and control treatments.

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Curt R. Rom, Jason McAfee, and Donn Johnson

Apple cultivar development is an important program necessary to sustain the existing fruit industry and stimulate new production systems for Arkansas and the region. The cultivar development program has two parts. First, currently available cultivars are tested with multiple trees for multiple years. Second, about 150 advanced selections from the Arkansas apple breeding program are evaluated in trials with multiple trees (2nd test) and in replicated trials (3rd test). The goal of both programs is to identify cultivars that have potential in the local production systems and for Arkansas' markets, and to identify those cultivars which are not adapted to the region. All cultivars and advanced selections are evaluated for ∂35 qualitative and quantitative characteristics, including time of bloom, time of harvest, length of harvest season, fruit aesthetic and internal quality, environmental adaptability especially to heat and high light, and insect and disease susceptibility. Primary diseases for which cultivars and selections are screened include fireblight, cedar apple rust, powdery mildew, black rot, white rot and bitter rot. Primary insect pests include mites, codling moth, plum curculio and Japanese beetle. Cultivars are evaluated in the field, under standard management conditions for five to seven years of production before summary evaluation. The program has identified cultivars including traditional cultivars, new cultivars, and heritage cultivars adaptable to the local and regional climates and suitable for those markets.

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Kristen Harper, Curt R. Rom, and Jason McAfee

As funding directed toward research has diminished, it has become vital seek other avenues of support to maintain long term field projects. To meet this need, the University of Arkansas Horticulture Department began the Friends of Fruit (FOF) program during 2004 engaging volunteers in conducting tree fruit field research. Volunteers were graduates of the Master Gardener program and executed tasks including data collection and plot maintenance. Objectives of this study were to evaluate the experiences and benefits to the volunteers and horticulture department, and to assess the success of the FOF program in providing assistance and support to research. All volunteers and facilitators were interviewed. Interview questions were designed to understand the motivation and level of volunteer activity, determine if training and supervision was adequate, and determine if ample recognition occurred. Volunteers sought experience and knowledge with fruit crops. Costs to volunteers included time and travel, conversely benefits included knowledge, experience and fellowship. Volunteers planned to repeat the program and were pleased with the recognition they received. Facilitators noted that volunteers had basic horticultural knowledge and the desire to learn. The program did call for improved task management and increased planning time by facilitators. The program succeeded in benefiting volunteers and horticultural research. The FOF volunteers contributed to fruit research by harvesting ≈4,000 kg of fruit samples and providing >200 hours of time.

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Jason D. McAfee and Curt R. Rom

Pesticides and alternative fruit thinners are needed for certified organic fruit growers. Transient reductions in photosynthesis (Pn) have proven an effective technique for fruit thinning. Pesticides can be detrimental to plant growth by Pn reduction. A two-part study was developed to measure plant response to foliar applications of sulfur compounds. In study 1, 2% concentrations of various sulfur compounds were observed for potential physiological or pesticidal effects. Foliar treatments were applied to vegetative apple trees grown under controlled environment conditions to study photosynthetic effects. No treatments significantly reduced CO2 assimilation (A) and stomatal conductance (gs). Copper sulfate, ammonium sulfate, and potassium sulfate significantly reduced evapotranspiration (Et) 7 days after treatment. No significance was observed for plant growth. In study 2, a 2% potassium sulfate concentration significantly reduced A 22 days after treatment; however, no differences were observed for Et and gs. Differences in plant growth were not significantly different among treatments.

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Mengmeng Gu, James A. Robbins, Curt R. Rom, and Jason McAfee

Japanese beetle (Popilla japonica Newman) has caused severe damage on a wide range of horticultural crops since its first introduction to the Eastern United States from Japan in 1916. Leaves are skeletonized by adult beetles feeding in masses, which makes this insect damage easy to identify. In Arkansas, Japanese beetle was first trapped in Washington County in 1997 and has reached epidemic proportions in the most recent three years. Leaf skelotonization and feeding preference on eighteen birch accessions by Japanese beetle were recorded in 2003 and 2004. There was a wide range from no feeding (0% leaf skelotonization) to high feeding preference (89% leaf skelotonization). Betula utilis var. jacquemontii and B. papyrifera `Renaissance Upright' had highest preference. Betula pendula `Laciniata' had no feeding damage from Japanese beetle.

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Hyun-Sug Choi, Curt R. Rom, Mengmeng Gu, and Jason McAfee

Seasonal variations of nutrient concentrations in soil and apple leaves, soil properties, weed density, and tree performance were observed for response to four groundcover managements systems: 1) mowed control; 2) plastic woven landscape fabric; 3) wood chip mulch; and 4) shredded commercial paper mulch. Soil sampled below the wood chip and shredded paper mulch treatments had higher NO3-N concentrations during the season. Soil below the shredded paper mulch had greater soil Ca, Na, and Zn than other treatments. Soil sampled below wood chip mulch had higher Mg and B. Leaf K was greater for trees grown with bark chip mulch than the other treatments. Overall, the seasonal patterns of N, P, and K decreased and had similar patterns as previously reported conventionally grown orchards. The leaf Ca and Mg increased during the season for all treatments. The concentration of other microelements had patterns similar among all treatments. Seasonal soil pH decreased during the season and was affected by treatments. During the season, water infiltration was faster into the soil covered with shredded paper mulch. The organic matter was greater in soil under the wood chip mulch at the 15-cm soil depth. Very little weed invasion occurred in the landscape fabric through August. Trees grown with shredded paper and wood chip mulch treatments had greater trunk cross-sectional area compared to trees grown under landscape fabric after 5 years; however, the latter treatment resulted in greater tree height, tree canopy spread, and fruit yield.

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Hector German Rodriguez, Jennie Popp, Curt Rom, Heather Friedrich, and Jason McAfee

Numerous apple (Malus ×domestica) research experiments have shown that organic apples can be both profitable and sustainable, especially in the Pacific northwestern United States. However, there is limited published research on the profitability of organic apple orchards in the southern U.S. region. Surveys of southern U.S. stakeholders have indicated that great opportunities exist for markets of both fresh and processed fruit, but significant challenges still exist. These challenges include a lack of information available on the economic impacts of different organic production practices and the potential returns available from organic production. In response to these challenges, we developed a user-friendly interactive economic decision support tool using spreadsheet software to simulate organic apple production in Arkansas and across the southern United States. The purpose of this interactive economic decision support tool is 2-fold: 1) to assist producers in the evaluation of costs, returns, and risks associated with their organic apple orchard and 2) to assess changes to cost, return, and risk as expected costs, prices, and/or yields change. The production budget components of the interactive economic decision support tool estimate variable and fixed costs, gross revenues, and net returns for 18 years of production. In addition, this interactive economic decision support tool provides economic analyses regarding: 1) the operation’s breakeven (price and yield) points, 2) sensitivity analyses or “what if” scenarios related to changes in costs and returns, and 3) risk assessment by calculating the probability of obtaining a positive net present value (NPV) over the life of the organic apple orchard. This manuscript describes the development of this interactive economic decision support tool and provides an example of how it works.