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Eric Simonne, Nadia Ouakrim and Arnold Caylor

Potato (Solanum tuberosum L.) is often produced as a nonirrigated crop in the southeastern United States. This practice makes tuber yields dependent on rainfall pattern and amount. An irrigation scheduling method based on a water balance and daily class A pan evaporation (Ep) was evaluated during 1996 and 1998 on a Hartsells fine sandy loam soil for `Red LaSoda' potatoes. Planting dates were 9 and 7 Apr. in 1996 and 1998, respectively, and standard production practices were followed each year. The model tested was (13 DAH + 191) * 0.5 ASW = D DAH-1 + [Ep * (0.12 + 0.023 DAH - 0.00019 DAH2) - RDAH - IDAH], where DAH was days after hilling, ASW was available soil water (0.13 mm/mm), D was soil water deficit (mm), R was rainfall (mm), and I was irrigation (mm). Controlled levels of water application ranging between 0% and 200% of the model rate were created with drip tapes. Four and seven irrigations were scheduled in 1996 and 1998, respectively. For both years, no interaction between irrigation regime and nitrogen rate was observed. Irrigation rate significantly influenced total yield and marketable yield (R 2 > 0.88, P < 0.01). Highest total yields occurred at 99% and 86% of the model rate in 1996 and 1998, respectively. These results show that supplementing rainfall with irrigation and controlling the amount of water applied by adjusting irrigation to actual weather conditions increased potato marketable yield. Over the 2-year period of the study, an average additional profit of $563/ha/year was calculated from costs and returns due to irrigation, suggesting that drip-irrigation may be economical for potato production.

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Eric H. Simonne, Joseph M. Kemble and Arnold W. Caylor

Most potato (Solanum tuberosum L.) is produced as a non-irrigated crop in the southeastern United States. This practice makes potato yields dependent on rainfall pattern and amount. An irrigation scheduling method based on a water balance and class A pan evaporation data (Ep) was evaluated in Spring 1996 on a fine sandy loam soil with `LaSoda' potatoes. Planting date was 9 Apr. and standard production practices were followed. The model was (12.7 DAH + 191) * 0.5 ASW = D(DAH-1) + [Ep (0.12 + 0.023 DAH - 0.00019 DAH*DAH) - R(DAH) - I(DAH)], where DAH is days after hilling (DAH = 0 on 14 May), ASW is available soil water (0.13 mm/mm), D is soil water deficit (mm), R is rainfall (mm) and I is irrigation (mm). Root depth expanded at a rate of 13 mm/day to a maximum depth of 305 mm. Root depth at hilling was 191 mm. Controlled levels of water application ranging between 0% and 161% of the model rate were created with drip tapes. The model scheduled irrigations on 35, 39, 43 and 49 DAH. On 85 DAH, potatoes were harvested and graded. Irrigation influenced total yield, marketable yield, and combined US #1 grades (P < 0.01; R 2 > 0.85). Mean marketable yields were 19, 28, and 21 t/ha for the 0%, 100%, and 160% irrigation rates, respectively. These results suggest that supplementing rainfall with irrigation and controlling the amount of water applied by adjusting irrigation to actual weather conditions could increase potato yields. Excessive water, as well as limiting water, reduced potato yields.

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Bob Ebel, David G. Himelrick, Arnold Caylor and Bryan Wilkins

The Environmental Protection Agency has developed regulations requiring municipalities to reduce the amount of solid wastes going into landfills. One potential outlet for yard waste is agriculture. This study was conducted during the first 6 years of orchard establishment to compare tree and fruit response of `Fuji', `Golden Delicious' and `Red Delicious' apple trees to composted yard waste and other conventional fertilizers. Calcium nitrate and urea were applied at 16.8, 33.6, and 67.3 kg·ha–1 N per year. Composted municipal yard waste was applied at 1.3-, 2.5-, and 5.0-cm depths, within the sod-free strip of the tree row. Yard waste promoted growth compared to calcium nitrate and urea allowing the trees to fill their allotted space earlier. Yield and yield efficiency were generally similar across all forms of fertilizers. Foliar N was not affected by the form of nitrogen used, did not vary across the different rates of calcium nitrate and urea, and was well within the range considered sufficient (1.8% to 2.5%) for all treatments. It is concluded that the accelerated growth by yard waste was not due to N nutrition. Other foliar element levels were not consistently affected by fertilizer form or rates for the three cultivars. Fruit weight, length/diameter ratio, firmness, and soluble solids were generally not negatively affected by the yard waste, although some fruit were slightly softer and soluble solids slightly lower than fruit from trees treated with calcium nitrate and urea. This study demonstrates that municipal yard waste may provide benefits to a fertilization management system for apple orchards by promoting early growth.

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Robert C. Ebel, Arnold Caylor, Jim Pitts and Bobby Boozer

Ethrel [(2-chloroethyl)phosphonic acid] was applied at 0, 100 or 200 ppm (mg·L-1) for 3 years to the early maturing `Empress' peach [Prunus persica (L.) Batsch] to determine if bloom delay by Ethrel reduces fruit weight at harvest. Trees were hand thinned at 0 or 3 weeks after full bloom to equalize cropload across Ethrel treatments and to determine if any reduction in fruit weight by Ethrel can be compensated by harvest with earlier thinning. Ethrel at 200 ppm (mg·L-1) delayed bloom by 3, 0, and 7 days in 1994, 1996 and 1997, respectively. Despite bloom delay, Ethrel did not delay harvest or reduce fruit weight. Thus, earlier hand thinning was not necessary. Ethrel did not affect blossom density and was not phytotoxic to vegetative or reproductive organs. These results indicate that even with the shorter fruit growth period of early maturing peach cultivars such as `Empress', there is sufficient time for fruit growth to recover on Ethrel treated trees so that fruit weight at harvest is not reduced.

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Eric Simonne, Bob Hochmuth, Jeff Simons, Edgar Vinson III and Arnold Caylor

Several okra (Abelmoschus esculentus) cultivars are now available as alternatives to the standards `Clemson Spineless' (open pollinated) and `Annie Oakley II' (hybrid). Based on the results of four trials involving 20 cultivars, `Mita', `Spike', `Green Best' and `North & South' should be added to the list of recommended cultivars for Alabama and Florida. The experimental `SOK 601' should also be included on that list, but on a for trial basis since it was evaluated only at one location. Other cultivars may perform well at specific locations. Differences among cultivars were also found for ease of harvest. `North & South' and `Baby Bubba' were the easiest and most difficult cultivars to harvest, respectively. The economic feasability of selecting a hybrid cultivar over an open-pollinated one and using plasticulture instead of bare ground was also examined in this study. Using hybrid seeds resulted in an average yield increase per harvest of 92 lb/acre (103 kg·ha-1), which exceeded the estimated 75 lb/acre yield (84 kg·ha-1) increase necessary to offset the additional cost of hybrid seeds. For reasons ranging from improved weed control, increased nutrient and water use efficiency, and double cropping, an increasing interest exists to produce okra with plasticulture, instead of bare ground as done traditionally. The average yield increase per harvest due to plasticulture over bare ground production was 196 lb/acre (220 kg·ha-1). Based on this number, it would take three harvests to produce the 540 lb/acre (605 kg·ha-1) yield increase necessary to offset the additional costs due to plasticulture.