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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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Monte L. Nesbitt, Robert C. Ebel, Douglas Findley, Bryan Wilkins, Floyd Woods, and David Himelrick

Containerized `Owari' satsuma mandarin (Citrus unshiu Marc.) on Poncirus trifoliata `Flying Dragon' rootstock were exposed to one of two acclimation regimes (cold acclimated and unacclimated) and frozen in a computer-controlled freezer to five different low temperatures. Whole plant survival was measured and compared to the results of four leaf and stem injury assays. Acclimating plants in growth chambers at 20 °C day and 10 °C night for 14 days, followed by 15 °C day and 4 °C night for 14 to 21 days resulted in an 81% and 80% increase in leaf and stem survival, respectively, when frozen to a low of -8 °C. Electrolyte leakage and phenolic leakage assays effectively detected changes in percent leaf survival, but the TTC stain assay, using leaf disks, did not. Stem survival was best predicted by the TTC assay, using the phloem as the indicator tissue for survival. Electrolyte leakage and phenolic leakage were also reliable assays for predicting stem survival, although survival percentages were different at the same electrolyte leakage values reported in other studies. The callus growth assay accurately predicted survival for cold acclimated satsuma mandarin stems only. Chemical name used: triphenyl tetrazolium chloride (TTC).

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Clint Wall, William Dozier, Robert C. Ebel, Bryan Wilkins, Floyd Woods, and Wheeler Foshee III

Kiwifruit (Actinidia deliciosa A. Chev. and Actinidia chinensis Planch) require winter chilling to complete rest and growing degree hours to grow. This study was conducted to compare the chilling requirement and growing degree hours for budbreak and floral development of two female cultivars of A. chinensis, ‘Golden Sunshine’ and ‘Golden Dragon', two female cultivars of A. deliciosa, ‘AU Fitzgerald’ and ‘Hayward', and two male cultivars of A. deliciosa, ‘AU Authur’ and ‘Matua'. In 2005 and 2006, shoot cuttings were made from dormant 1-year canes at nodes 6 to 20, starting from the basal end of canes and held in cold storage at 4 °C. Cuttings were removed from storage and flowering was forced in a greenhouse maintained at 25 °C. Maximum budbreak was determined to be 700 h for ‘Golden Sunshine’, 800 h for ‘Golden Dragon’ and ‘AU Fitzgerald’, and 900 h for ‘Hayward’, ‘Matua’, and ‘AU Authur’. Growing degree hour to first budbreak were 9,500 h for ‘Golden Dragon’ and 15,000 h for ‘Golden Sunshine’, with the correlation of determination too low for the other cultivars. The high heat requirement for ‘Gold Sunshine’ would reduce the risk of injury by late spring frosts. Bloom period of both male cultivars overlapped with bloom periods for all cultivars except ‘Golden Dragon’ for fully mature vines in the field.

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Robert C. Ebel, Bryan Wilkins, David Himelrick, Tom Beckman, Andy Nyczepir, and Jim Pitts

Twelve peach rootstocks including `Lovell', `Nemaguard', `Flordaguard', `14DR51', five `Guardian' (BY520-9) selections, and three BY520-8 selections, were evaluated under field conditions to determine their effect on performance of `Cresthaven' peach. The trees were planted in 1994. Trunk cross-sectional area of BY520-8 selections SL1923 and SL4028 was 28% larger than the rest of the rootstocks, which were similar. There was no crop in 1996 due to late spring frost. Yield in 1997 and 1998 was higher for SL1923 because of higher cropload than the rest of the rootstocks, which were similar. Yield efficiency varied across years and rootstocks. Fruit weight varied among rootstocks but all were commercially acceptable. Harvest date was advanced by two days for some rootstocks compared to Lovell and none were delayed. Percent red blush, soluble solids and firmness varied among rootstocks, but none demonstrated superior quality in all of these parameters as compared to Lovell. Ring nematode population densities were above the threshhold considered to be critical for onset of PTSL for all rootstocks in 1997 and 1998. Tree survival was at or above 86% for all rootstocks and death was not correlated with ring nematode density No trees developed symptoms characteristic of Peach Tree Short Life disease complex. Guardian selections performed adequately compared to the commonly used commercial rootstocks in this study, however, the yield date are from 2 years only.

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Floyd M. Woods, William A. Dozier, Robert C. Ebel, Raymond Thomas, Monte Nesbitt, Bryan S. Wilkins, and David G. Himelrick

Changes in fruit quality attributes and antioxidative properties from six cultivars of thornless blackberries (Rubus sp.) (`Apache', `Arapaho', `Chester', `Loch Ness', `Navaho', and `Triple Crown') during four different ripening stages (red, mottled, shiny-black, and dull-black) were determined under Alabama growing conditions. Berry fruit samples were evaluated for pH, titratable acidity, total soluble solids, TSS/TA ratio, soluble sugars, vitamin C (reduced, oxidized and total), and antioxidant capacity (measured as trolox equivalent antioxidant capacity, TEAC). Significant variation among cultivars were noted in fruit quality attributes and antioxidative properties, which were influenced by maturity at harvest. An increase in fruit pH concomitant with a decline in titratable acidity (TA) was observed during ripening for all cultivars. Total soluble solids (TSS) values increased from 5.7% to 11.6%, with associated TSS/TA ratio values ranging from 11.92 to 63.56 in ripening fruit. Highest reducing and total sugar content were contained in dull-black fruit. Vitamin C content either declined or remained unchanged with ripening, and the pattern was dependent on cultivar, maturity at harvest and form determined. In general, antioxidant activity declined between red and dull-black ripening stages. The results suggest that the TSS/TA ratio may provide the best maturity index in determining optimal eating quality and antioxidant capacity in terms of TEAC value the best indicator of optimal nutritional quality as influenced by maturity at harvest.

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Michael F. Polozola II, Daniel E. Wells, J. Raymond Kessler, Wheeler G. Foshee, Amy N. Wright, and Bryan S. Wilkins

An experiment was conducted to determine the effects of banded phosphorus (P) applications at differing rates in irrigated and nonirrigated pecan (Carya illinoinensis) plots on P movement within the soil, P uptake and movement within pecan trees, and the yield and quality of nuts. On 20 Mar. 2015, P applications of 0 kg·ha−1 (0×), 19.6 kg·ha−1 (1×), 39.2 kg·ha−1 (2×), and 78.5 kg·ha−1 (4×) were administered to bands of triple superphosphate to randomly selected trees in nonirrigated and irrigated plots of a ‘Desirable’ orchard bordered by ‘Elliot’ trees. When P was applied at the 2× and 4× rates, the total soil test P decreased linearly by 35% and 54%, respectively, in nonirrigated plots and by 41% and 59%, respectively, in irrigated plots over the course of the experiment. There was no change in soil test P over time at the 0× rate for either irrigation regimen; however, at the 1× rate, soil test P decreased 44% in the irrigated plot but did not change in the nonirrigated plot. The largest linear decrease of the soil test P from the start of the experiment to the end of the experiment occurred in the top 0 to 7.6 cm. In contrast, soil test P at a depth of 15.2 to 22.9 cm decreased linearly by 23% in the nonirrigated plot, but it did not decrease over time in the irrigated plot. Increasing the P application rate increased foliar P quadratically in the nonirrigated plot, but only the 4× application rate increased foliar P compared with the 0× control. In the irrigated plot, foliar P concentrations decreased linearly from 2015 to 2017, and foliar P concentrations were not influenced by the P application rate. No differences in pecan yield or quality were observed in either irrigated or nonirrigated plots. Overall, P banding may not be the most sustainable way to increase foliar concentrations of P quickly or to maintain concentrations of the nutrient in the long term.

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Esmaeil Fallahi, Bahar Fallahi, James R. McFerson, Ross E. Byers, Robert C. Ebel, Robert T. Boozer, Jim Pitts, and Bryan S. Wilkins

Effects of Tergitol-TMN-6 surfactant on blossom thinning (fruit set), fruit quality, and yield were studied in different cultivars of peach (Prunus persica [L.] Batsch) during 2003 to 2005, and in one cultivar of nectarine Prunus persica [L.] in one orchard and one cultivar of plum (Prunus domestica [L.]) in two orchards in 2004. In addition to Tergitol-TMN-6, effects of Crocker's fish oil (CFO) alone in three peach cultivars or in combination with lime sulfur in a nectarine cultivar were studied on fruit set, quality, and yield. Tergitol-TMN-6 at 5 mL·L–1 or higher rates, applied at about 75% to 85% bloom, reduced fruit set without russeting peach fruit. Peach fruit size was often increased by Tergitol-TMN-6 treatment. Applications of Tergitol at 20 mL·L–1 or 30 mL·L–1 excessively thinned peaches. Tergitol-TMN-6 at all rates burned foliage, but the symptoms disappeared after a few weeks without any adverse effects on tree productivity. Tergitol-TMN-6 at 7.5 mL·L–1 or 10 mL·L–1, applied either once at about 80% to 85% bloom or twice at 35% bloom and again at 80% to 85% bloom, reduced fruit set without any fruit russeting in nectarine. Tergitol-TMN-6 at 7.5 mL·L–1 to 12.5 mL·L–1 reduced fruit set in `Empress' plum. CFO at 30 mL·L–1 was effective in blossom thinning of some peach cultivars. A combination of lime sulfur and CFO was not effective in blossom thinning of nectarine. Considering results from several orchards in different locations in the Pacific Northwest over 3 years, Tergitol-TMN-6 is an excellent blossom thinner for peach, nectarine, and plum at rates of 7.5 to 12.5 mL·L–1, sprayed at a spray volume of 1870.8 L·ha–1 when about 75% to 85% blooms are open.

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Floyd M. Woods*, William A. Dozier Jr., Robert C. Ebel, David G. Himelrick, Cecilia Mosjidis, Raymond H. Thomas, Bryan S. Wilkins, and James A. Pitts

The relationship between fruit maturation and accumulation of hydrogen peroxide (H2 O2), lipid peroxidation, ethylene (C2 H4) production, antioxidant activity (hydrophilic, lipophilic and total) and the antioxidant enzyme ascorbate peroxidase (APX, EC 1.11.1.11) in fruit pericarp tissue of `Chandler' (Fragaria × ananassa Duch.) strawberry were measured. `Chandler' fruit pericarp maturation and ripening were accompanied by a decline in H2 O2 content early in fruit development followed by a rapid accumulation. An increase in membrane lipid peroxidation (thiobarbituric acid reactive substances, TBARS) coincided with accumulation of H2 O2, which preceded a rise in C2 H4 production. In general, antioxidant activity declined as fruit matured and ripened. APX enzyme activity increased by 2-fold and peaked at the pink stage of development and then gradually declined with ripening. H2 O2 may serve as a signal molecule to initiate the cascade of oxidative processes during maturation and ripening. APX enzyme activity during maturation and ripening was not substantial and thus, may not have a role in alleviating accumulation of H2 O2 and subsequent events related to oxidative senescence in fruit pericarp. To our knowledge, this is the first study to present fractionated antioxidant activities (HAA, LAA and TAA) from strawberry pericarp as assessed by the ABTS∼+ radical cation assay. A fundamental understanding of the mechanisms involved in the senescent related-oxidative changes during strawberry fruit ontogeny in relation to quality and nutrition is discussed.