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Timothy Coolong and Mark A. Williams

Eight cultivars of onion (Allium cepa) representing, long, intermediate, and short-day types were evaluated for their ability to be overwintered in Kentucky. Onion seedlings were transplanted in Nov. 2007 and Oct. 2008. Plants were covered with spunbonded rowcovers or wheat (Triticum sp.) straw mulch in December and mature bulbs were harvested in June and July. Bulbing was initiated in ‘Yellow Granex’ (short-day) during transplant production, thus it was not planted in the field in either year of the experiment. The use of rowcovers compared with straw mulch increased survival rates in all cultivars. The intermediate-daylength cultivars, Candy, Superstar, and Expression, had greater percentages of bolting when grown under rowcovers compared with straw mulch. This resulted low marketable yields despite high survival rates. Rowcover/mulch treatment and cultivar interacted (P ≤ 0.05) to affect yields. The long-day cultivars, Olympic, Ailsa Craig, and Walla Walla had the highest yields when grown under rowcovers. ‘Olympic’, the highest yielding cultivar, produced a large percentage of jumbo-sized bulbs. The short-day cultivar, WI-131, had low survival rates and yields under rowcovers and straw mulch. Pungencies were lowest in ‘WI-131’ and ‘Olympic’. In general, long-day onion cultivars had high rates of survival, low rates of bolting, and higher yields compared with intermediate-day types. This suggests that they would be preferred for overwinter production in Kentucky.

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Mark W. Jarecki, David J. Williams and Gary J. Kling

Growers, nurseries, landscape contractors and installers, and those responsible for maintenance have observed a trend that trees are too deep within the root ball. This study addresses the relationship between planting depth and its effect on tree survival, root growth, root architecture, and caliper growth. The experiment was initiated to determine the effect of planting depth on nursery-grown trees. Three-year-old, 2.1–2.7 m, bare-root liners of Acer platanoides `Emerald Lustre', Fraxinus americana `Autumn Purple', Fraxinus pennsylvanica `Patmore', and Gleditsia triacanthos f. inermis `Shade Master' were planted in April 2004 in a completely randomized design with 20 replications per treatment per species. The trees were selected so that the distance between the graft union and the trunk flare was consistent. Trees were planted with the graft union 15.2 cm below the soil surface, or with the base of the graft union at the finished grade or with the trunk flare at the finished grade. The trees were grown in a nursery field setting with minimal supplemental watering. There were no differences in stem caliper growth at the end of two seasons in any of the four species. Root dry mass, stem elongation, and rooting structure were determined on a representative sample of trees while others were planted into the landscape for a long-term study of the effects of the original planting depth on landscape performance.

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Zheng Wang, Mark Williams, Krista Jacobsen and Timothy Coolong

Trials were conducted in 2011 and 2012 with ‘Aristotle’ bell pepper (Capsicum annuum L.) grown under different tillage methods and irrigation regimes in organically and conventionally managed production systems. Treatments consisted of strip tillage or plastic mulch in well-watered or water-restricted irrigation regimes. Within organic and conventional production systems, the study was arranged as a split-plot randomized block design with strip tillage or plastic mulch as the main plot and irrigation regime as subplot. Leaf water potential (ΨL), soil penetration resistance (compaction), volumetric water content (VWC), soil temperature, and pepper yield were measured. Soil VWC was greater in strip-tillage plots compared with plastic mulch plots under both well-watered and water-restricted conditions for plots in the organic system in 2011 and conventional system in 2012. In addition, soil VWC was numerically lower, if not always statistically different, in water-restricted plots compared with well-watered plots. The trend of soil temperatures within each production system were similar in 2011 and 2012, with plastic mulch plots having slightly higher soil temperatures than strip tillage, despite using white-on-black plastic mulch. Midday ΨL was affected by water regime, with well-watered plants having a significantly lower ΨL than water-restricted plants; however, there were no effects of irrigation on predawn ΨL. Tillage method and sampling location (between row and within row) significantly interacted to affect soil penetration resistance in 2011 and 2012. There was a significant interaction of tillage by irrigation regime on yield within conventional systems in both years, but not in organically managed plots. In 2011, yield data also indicated that the date at which 50% of marketable fruit were harvested (yield_mid) were later for strip–tillage-grown plants than plastic mulch–treated plants within conventional and organic production systems, respectively.

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Elsa S. Sánchez, Ermita Hernández, Mark L. Gleason, Jean C. Batzer, Mark A. Williams, Timothy Coolong and Ricardo Bessin

The goal of this study was to develop a systems-based strategy for organic muskmelon (Cucumis melo var. reticulatus) in Pennsylvania (PA), Iowa (IA), and Kentucky (KY) to manage bacterial wilt (Erwinia tracheiphila) and nutrients while safeguarding yield and enhancing early harvest. Spunbond polypropylene rowcovers deployed for different timings during the growing season were evaluated for suppressing bacterial wilt and locally available compost was applied based on two different estimated rates of mineralization of organic nitrogen (N) to manage nutrients. In KY only, the use of rowcovers suppressed bacterial wilt incidence compared with not using rowcovers. However, the timing of rowcover removal did not impact wilt incidence. Under lower cucumber beetle [striped cucumber beetle (Acalymma vittatum) and spotted cucumber beetle (Diabrotica undecimpunctata howardi)] pressure in PA and IA, rowcovers did not consistently suppress season-long incidence of bacterial wilt. In four of five site-years in PA and IA, more marketable fruit were produced when rowcovers were removed 10 days after an action threshold (the date the first flower opened in PA; the date when ≥50% of plants in a subplot had developed perfect flowers in IA and KY) than when no 10-day delay was made or when no rowcovers were used. In addition, the no-rowcover treatment consistently had lower weight per marketable fruit. In KY, the same action threshold without the 10-day delay, followed by insecticide applications, resulted in the largest number of marketable fruit, but did not affect marketable fruit weight. In PA, marketable yield was higher using compost compared with the organic fertilizer in 1 year. No yield differences were observed by nutrient treatments in 2 years. In IA, marketable yield was lower with the low amount of compost compared with the organic fertilizer and yields with the high amount of compost were not different from the low amount or the organic fertilizer in the year it was evaluated. In KY, marketable yield was unaffected by the nutrient treatments in the year it was evaluated. Given these results, muskmelon growers in PA, IA, and KY who use compost may choose the lower compost rate to minimize production costs. Overall, these findings suggest that rowcover-based strategies for organic management of bacterial wilt need to be optimized on a regional basis, and that fertilization with compost is compatible with these strategies.

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Barbara E. Liedl*, John Bombardiere, Melissa L. Williams, Amanda Stowers, Christopher Postalwait and J. Mark Chatfield

Fertilizer costs and increased awareness of non-point source pollution run-off amplify the pressures on farm economics. Intensive farming operations provided the impetus for our study using effluent from anaerobic thermophilically digested poultry litter as a potential fertilizer. Five fertilizer treatments were used: unfertilized control, pelletized municipal sludge, commercial crop specific products, 1x digested solids and 2x digested solids. All four applications of fertilizer were equalized for nitrogen based on commercial product recommendations. Beds treated with 2x solids accumulated higher percentage of organic matter over the 5-year period. A statistically significant increase in phosphorus was found in the solids beds in 2003. Beds with 2x solids showed statistical significance for Mg, Zn and Cu. Fertilizer trials included blueberries, tomatoes, potatoes, and sweet corn. Potato fresh weight was not significantly different in 2002 or 2003, but was in 2001. Tomato fruit number was not significantly different in 2001 or 2003, but was in 2002. Tomato fresh weight for 2x solids was not significantly different from the commercial or pelletized sludge treatments in 2002 and 2003 suggesting that tomato may discriminate between treatments. Commercial and pelletized sludge fertilizers were statistically better for sweet corn fresh ear weight and number of ears in 2002 and 2003. Blueberry yields were not significantly different between treatments for any year. As this is a perennial crop, it may be several years before a significant difference is observed. While not a total solution, our research shows the effectiveness of digested poultry litter as part of a nutrient management program; making livestock residuals a nutrient resource which offers the potential for organic use.

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Derek M. Law, A. Brent Rowell, John C. Snyder and Mark A. Williams

A 2-year field study in Lexington, Ky., evaluated weed control efficacy and influence on yields of several organic mulches in two organically managed bell pepper (Capsicum annuum) production systems. Five weed control treatments [straw, compost, wood chips, undersown white dutch clover (Trifolium repens) “living mulch,” and the organically approved herbicide corn gluten] were applied to two production systems consisting of peppers planted in double rows in either flat, bare ground or on black polyethylene-covered raised beds. In the first year, treatments were applied at transplanting and no treatment was found to provide acceptable season-long weed control. As a result, bell pepper yields in both production systems were very low due to extensive weed competition. First year failures in weed control required a modification of the experimental protocol in the second year such that treatment application was delayed for 6 weeks, during which time three shallow cultivations were used to reduce early weed pressure and extend the control provided by the mulches. This approach increased the average weed control rating provided by the mulches from 45% in 2003 to 86% in 2004, and resulted in greatly improved yields. In both years, polyethylene-covered raised beds produced higher yields than the flat, bare ground system (8310 lb/acre compared to 1012 lb/acre in 2003 and 42,900 lb/acre compared to 29,700 lb/acre in 2004). In the second year, the polyethylene-covered bed system coupled with mulching in-between beds with compost or wood chips provided excellent weed control and yields. When using the wood chip mulch, which was obtained at no cost, net returns were $5587/acre, which is similar to typical returns for conventionally grown peppers in Kentucky. Net returns were substantially decreased when using compost due to the purchase cost. Results from this study indicate that shallow cultivation following transplanting, combined with midseason mulch application, resulted in high yields in an organically managed bell pepper system that were comparable to yields of most varieties grown conventionally in a variety trial conducted on the same farm.

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Mark A. Ritenour, Ellen G. Sutter, David M. Williams and Mikal E. Saltveit

This study was undertaken to determine if endogenous IAA content and axillary bud development correlate with phenylalanine ammonia-lyase (PAL) induction and russet spotting (RS) susceptibility among RS susceptible and resistant cultivars of Iceberg lettuce (Lactuca sativa L.). Final levels of ethylene-induced PAL activity and RS development were highly correlated among cultivars, field conditions, and harvest dates. Harvested Iceberg lettuce midribs contained relatively low amounts of free IAA (maximum of 5.2 ng·g-1 fresh weight). There was poor correlation between free IAA content in lettuce leaf midribs and final RS development among all cultivars, growing conditions, and harvest dates. Axillary bud development, as measured by the number of visible buds per head, bud weight, or bud length, were not significantly correlated with final RS development or midrib IAA content. Cultivars with higher initial free IAA content lost much of their IAA after 8 days storage at 5C in air ± ethylene.

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Timothy Coolong, Derek M. Law, John C. Snyder, Brent Rowell and Mark A. Williams

Thirty-eight leafy greens, eight kale (Brassica oleracea acephala group), nine mustard (Brassica juncea), six arugula (Eruca sativa), five swiss chard (Beta vulgaris var. cicla), five collards (B. oleracea acephala group), and five turnip (Brassica rapa ssp. rapa) varieties were evaluated during Spring and Fall 2007–08 to determine suitability for organic production with respect to yield and stability. Trials were conducted on certified organic land using organic production practices. For mustard, kale, collards, and arugula, there were significant variety by season by year interactions. Despite these interactions, some varieties consistently performed well throughout the trial. ‘Florida Broadleaf’ was the highest yielding mustard in three of the four seasons evaluated. ‘Siberian’, ‘White Russian’, and ‘Red Russian’ were in the highest yielding group of kale varieties for overall yield. For collards, ‘Georgia/Southern’ and ‘Flash’ were part of the highest yielding group as determined by Duncan’s multiple range test in three of the four seasons examined. Turnip and swiss chard had significant year by variety interactions. Overall yields of ‘Alamo’ and ‘Alltop’, both F1 hybrids, were better than other turnip varieties assessed. Despite the interaction, ‘Fordhook Giant’ had superior yields in both years of the study. Arugula performance was significantly and negatively affected in Spring 2008. Overall, ‘Astro’, ‘Apollo’, and ‘Arugula’ had the greatest yields. This trial was designed to provide recommendations specifically for organic growers marketing directly to consumers.

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Amanda Skidmore, Neil Wilson, Mark Williams and Ric Bessin

Pest management in cucurbit (Cucurbitaceae) cropping systems is challenging. As a result, pesticides are heavily used for managing insect pests and diseases. This work focused on the application of integrated pest management (IPM) techniques to control pests and reduce reliance on insecticide sprays while maintaining the quality and quantity of marketable yields in two commonly grown cucurbit crops: muskmelon (Cucumis melo) and summer squash (Cucurbita pepo). Plasticulture (raised beds covered in black plastic mulch) and strip tillage, two soil management systems commonly used for cucurbit IPM production, were compared to determine their impact on yield and pest numbers during the 2013–14 growing seasons. Additionally, the use of early season rowcovers and their impact on yield and pest pressure were investigated. Plasticulture use increased marketable yields compared with strip tillage for both summer squash and muskmelon, but strip tillage resulted in fewer total pests for both crops. Rowcover use did not have a consistent effect on insect pest numbers and showed a negative impact on the yield of both summer squash and muskmelon. No significant impacts on yield were observed when the interaction between rowcovers and the tillage system was investigated. The use of rowcovers impacted pest numbers, but these impacts were not consistent between insect pest species. Insecticide use was reduced in covered treatments, but only by one application. We concluded that these management techniques have the potential to be used in an IPM system, but the reduced marketable yield of strip tillage systems may reduce the adoption of this IPM technique for these crops.

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Mark A. Williams, John G. Strang, Ricardo T. Bessin, Derek Law, Delia Scott, Neil Wilson, Sarah Witt and Douglas D. Archbold

Although the interest in and production acreage of organic fruit and vegetables has grown in recent years, there are questions about the viability of perennial crops such as apple (Malus ×domestica) in an organic system in Kentucky because of the long, hot, and humid growing season. Thus, the objective of this project was to assess the severity of the challenges to organic apple production in Kentucky. A high-density, organic apple orchard was established in 2007 in the University of Kentucky Horticultural Research Farm in Lexington. The orchard of apple scab (Venturia inaequalis)–resistant ‘Redfree’, ‘Crimson Crisp’, and ‘Enterprise’ trees on ‘Budagovsky 9’ (B.9) rootstock, trained in a vertical axis system, was managed using organically certified techniques and materials for disease and insect control since its inception. Tree growth, tree and fruit injury from insect pests and diseases, and yield over the period 2011–13 were studied. Periodic, shallow cultivation kept the ground beneath the trees free of vegetation once the lower limbs were pulled up and away from the path of the equipment. Vole (Microtus sp.) damage was a continuing problem despite the use of trunk guards and cultivation to remove habitat around the trees. Total fruit yield ranged from 1.2 to 8.1 kg/tree across years and cultivars, with the marketable proportion of the total yield averaging 68% for Redfree and 43% for Crimson Crisp and Enterprise over the 3-year period. The unmarketable fruit exhibited a high incidence of plum curculio (Conotrachelus nenuphar) damage, with generally less damage from codling moth (Cydia pomonella) and sooty blotch (Glosodes pomigena)/flyspeck (Schizathyrium pomi). In addition, in two of the three seasons, ‘Crimson Crisp’ and ‘Enterprise’, which were harvested at later calendar dates then ‘Redfree’, had significant levels of powdery mildew (Podosphaera leucotricha) injury, ‘Enterprise’ had significantly greater bitter rot (Glomerella cingulata), and ‘Crimson Crisp’ showed fruit and foliar damage from cedar apple rust (Gymnosporangium juniperi-virginianae). Because ‘Redfree’ was the only cultivar with an acceptable marketable proportion of the fruit crop, the use of early ripening disease-resistant apple cultivars may have the greatest potential for successful organic apple production in Kentucky and the surrounding region.