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Alan R. Biggs and Gregory M. Peck

Three separate experiments were conducted to test standard calcium chloride salt (CaCl2) rates and several new formulations of calcium (Ca) for amelioration of bitter pit, a Ca-related physiological disorder that affects fruit of many apple (Malus ×domestica) cultivars, including the popular cultivar Honeycrisp. Even small amounts of bitter pit damage make apples unmarketable. We evaluated various formulations of Ca to compare their effectiveness in controlling bitter pit, including proprietary Ca products (InCa™, Sysstem-Cal™, Vigor-Cal™, XD10, and XD505) with and without antitranspirant. Calcium chloride is the most common Ca product used to reduce bitter pit incidence, but it has negative impacts, such as phytotoxicity and corrosiveness. Of the products that were tested in 2011, XD10 at the high rate and XD505 are candidates for future study. In 2012, both the CaCl2 and XD10 treatments had lower bitter pit severity than the nontreated control, but only the CaCl2 treatments had a lower total percentage of fruit with bitter pit compared with the control. The antitranspirant reduced bitter pit incidence in one of three treatments. Full season Ca treatments and higher rates (up to 23.5 lb/acre per season of elemental Ca) are needed to significantly reduce bitter pit incidence in ‘Honeycrisp’ apples in the mid-Atlantic United States.

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Ashley A. Thompson and Gregory M. Peck

In the Mid-Atlantic, mineral nitrogen (N) fertilizers are applied in high-density apple (Malus ×domestica Borkh.) orchards to increase tree vegetative growth and achieve earlier fruiting. However, when applied in excess of plant needs, N fertilizer applications are an unnecessary expense and may lead to N leaching and groundwater pollution. Therefore, it is necessary to develop orchard fertilization programs that simultaneously provide adequate crop nutrition and minimize N loss into the environment. Nitrogen was applied in each of 3 years to newly planted ‘Red Delicious cv Schlect’/‘M.26’ trees at 67 kg N/ha/year in six fertilizer treatments: 1) two equal applications of granular calcium nitrate [Ca(NO3)2]; 2) chicken litter compost; 3) yardwaste compost; 4) a combination of chicken litter compost and granular Ca(NO3)2 with equal amounts of N from each fertilizer; 5) a combination of yardwaste compost and granular Ca(NO3)2 with equal amounts of N from each fertilizer; and 6) fertigation which consisted of eight weekly applications of solubilized Ca(NO3)2. Nonfertilized trees served as the control. In the third year of this experiment, the two chicken litter compost treatments had the greatest soil extractable P, the yardwaste compost treatment had the greatest soil extractable K, both full-rate compost treatments had greater soil extractable Mg than the other treatments, and all four compost treatments had greater soil extractable Mn than the treatments without compost. The four compost treatments also had greater soil extractable Ca and B than treatments without compost. By the third year of the experiment, the four compost treatments also had greater soil organic matter (OM) and soil C (with the integrated chicken litter compost treatment having similar soil C to the other treatments). Potentially mineralizable nitrogen and soil microbial biomass were similar among the treatments over the course of this experiment. The full rate chicken litter compost treatment and both yardwaste compost treatments had greater soil microbial respiration in 2015. The fertigation treatment performed similarly to the treatment where Ca(NO3)2 was applied as a granular product to the soil. Treatment differences found for the soil properties did not translate to increased tree size or leaf N content, suggesting that the trees were able to acquire sufficient N from the soil under all of the treatments. Our results suggest that applying fertilizers to fine textured soil with relatively high OM may not increase apple tree growth or productivity within the first 3 years after planting. In addition, compost applications can improve many soil properties, but these differences may not result in improved orchard productivity within 3 years.

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Gregory Peck, Ian M. Merwin, Emily Vollmer, and Kristine Averill

Apple growers in New York lack the tools to produce high quality fruit for the organic or IFP marketplace. We are systematically evaluating OFP and IFP systems for pest control efficacy, fruit and soil quality, environmental impacts, and economic sustainability, in an orchard of disease-resistant `Liberty' on M.9 rootstock. The OFP system follows USDA-NOP standards and the IFP system follows newly developed NY IFP standards. In the first year of this study (2004), both systems were equally productive, but variable costs for OFP were twice that of IFP, due to 11 kaolin applications, while returns were comparable. In 2005, OFP yields were 25% greater than IFP yields, but 30% of OFP fruit was unmarketable largely due to insect damage. This loss, plus small fruit size, resulted in OFP returns of $5432 per hectare, about half the IFP returns. With only four kaolin applications in 2005, OFP costs were $2437 per hectare, marginally greater than the $2083 per hectare costs for IFP apples. Harvest maturity indices were similar and peak fruit quality was attained in both systems in early Oct. In 2004, consumer panelists could not detect differences between fruit from the two systems, but in 2005 panelists rated OFP apples as sweeter, more tart, better flavored, and more acceptable overall. Antioxidant activity, total phenolics concentrations, and mineral content of apples were similar between systems in both years. Values for all essential plant nutrients, organic matter content, pH, and CEC were also equivalent in each system both years. Cultivation was likely responsible for lowering the bulk density, soil strength, and aggregate stability of the OFP top soil in 2005. While OFP remains very challenging, IFP can be implemented successfully in New York orchards.

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Gregory M. Peck, Ian A. Merwin, Michael G. Brown, and Arthur M. Agnello

A systems-based approach was used to evaluate integrated (IFP) and organic fruit production (OFP) (during and after the transition period) in an established high-density commercial orchard of disease-resistant ‘Liberty’ apples (Malus ×domestica Borkh.). Agroecological and economic evaluations included: yields, tree growth, leaf nutrient levels, arthropod and cosmetic fruit damage, environmental impacts, variable costs of production, and potential crop value using both direct market and wholesale market prices. Cumulative yields (2004–2007) of both harvested and total (harvested + dropped) fruit were not different between the two systems. Tree size (trunk cross-sectional area) was not consistently different between the production systems. The IFP-grown apples had between 3% and 6% insect damage (within normal percentages for this region) and between 3% and 17% total damage (either internal or cosmetic). The OFP-grown apples had between 3% and 25% insect damage and 3% to 75% total damage, varying greatly from year to year. In 2006, superficial blemishes, caused by diseases and scarfskin, were extensive on OFP-grown fruit. Using the Environmental Impact Quotient, the potential negative environmental impacts were estimated to be six times greater in the OFP system, largely as a result of the use of lime sulfur and fish oil for thinning and the large quantity of kaolin clay used for pest control. Partial budgets of both systems estimated variable production expenses to be 9% greater for OFP. Sales value was estimated to be 6% greater for OFP than IFP using direct market prices (e.g., farm stand or farmers' market) and 11% greater for IFP than OFP using wholesale market prices. A 56% premium was used to calculate the OFP crop value in the third and fourth years (fruit could have been sold with an organic label after 36 months from the last organically prohibited material). Four years of evaluation suggested that IFP could be widely implemented in the northeastern United States, but the lack of market incentives might impede its adoption. Producing disease-resistant apples under an OFP system also showed potential for success, but a price premium would be needed to offset the reduced profitability incurred from arthropod pests, poor fruit finish, and small fruit size.

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Gregory M. Peck, Candace N. DeLong, Leon D. Combs, and Keith S. Yoder

Although demand for organic produce continues to increase in the mid-Atlantic, few apple (Malus ×domestica Borkh.) growers in the region have adopted organic management practices due to the considerable disease, insect, and weed pressure, as well as the lack of effective crop load management tools. In this study, lime sulfur (LS) and Regalia® (R) were applied in different sequences (i.e., LS/LS, LS/R, R/R, and R/LS), each in a mixture with JMS Stylet-Oil, to chemically thin apple flowers in an organically managed ‘Honeycrisp’/‘MM.111’ orchard. There was also a nontreated control, a “grower standard” control (LS at 11 mm fruitlet diameter), and a hand-thinned control. The treatments were evaluated for their ability to reduce crop load, as well as to control powdery mildew [Podosphaera leucotricha (Ellis & Everh.) E. S. Salmon], cedar apple rust (Gymnosporangium juniperi-virginiana Schwein.), and quince rust (Gymnosporangium clavipes Cooke & Peck). All treatments reduced crop load compared with the nontreated control, and after the first application of LS or R, the number of fertilized king blooms was reduced and fertilization was prevented in all side blooms. All bloom thinning treatments had more fruit peel russet than the control and russet was more severe when LS was one of the applications. Bloom thinning applications of LS and R did not reduce powdery mildew leaf infection compared with the nontreated control. Cedar apple rust incidence was reduced by all bloom thinning treatments, though some lesions were detected in all treatments. There were minimal quince rust infections in any of the treatments, including the nontreated control. These results suggest that when LS and/or Regalia® are mixed with JMS Stylet-Oil and applied as bloom thinners, they can reduce crop load, and, as a secondary benefit, they can also decrease cedar apple rust incidence from infections that occur during bloom.

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Gregory M. Peck, Preston K. Andrews, John P. Reganold, and John K. Fellman

Located on a 20-ha commercial apple (Malus domestica Borkh.) orchard in the Yakima Valley, Washington, a 1.7-ha study area was planted with apple trees in 1994 in a randomized complete block design with four replications of three treatments: organic (ORG), conventional (CON), and integrated (INT). Soil classification, rootstock, cultivar, plant age, and all other conditions except management were the same on all plots. In years 9 (2002) and 10 (2003) of this study, we compared the orchard productivity and fruit quality of `Galaxy Gala' apples. Measurements of crop yield, yield efficiency, crop load, average fruit weight, tree growth, color grades, and weight distributions of marketable fruit, percentages of unmarketable fruit, classifications of unmarketable fruit, as well as leaf, fruit, and soil mineral concentrations, were used to evaluate orchard productivity. Apple fruit quality was assessed at harvest and after refrigerated (0 to 1 °C) storage for three months in regular atmosphere (ambient oxygen levels) and for three and six months in controlled atmosphere (1.5% to 2% oxygen). Fruit internal ethylene concentrations and evolution, fruit respiration, flesh firmness, soluble solids concentration (SSC), titratable acidity (TA), purgeable volatile production, sensory panels, and total antioxidant activity (TAA) were used to evaluate fruit quality. ORG crop yields were two-thirds of the CON and about half of the INT yields in 2002, but about one-third greater than either system in 2003. High ORG yields in 2003 resulted in smaller ORG fruit. Inconsistent ORG yields were probably the result of several factors, including unsatisfactory crop load management, higher pest and weed pressures, lower leaf and fruit tissue nitrogen, and deficient leaf tissue zinc concentrations. Despite production difficulties, ORG apples had 6 to 10 N higher flesh firmness than CON, and 4 to 7 N higher than INT apples, for similar-sized fruit. Consumer panels tended to rate ORG and INT apples to have equal or better overall acceptability, firmness, and texture than CON apples. Neither laboratory measurements nor sensory evaluations detected differences in SSC, TA, or the SSC to TA ratio. Consumers were unable to discern the higher concentrations of flavor volatiles found in CON apples. For a 200 g fruit, ORG apples contained 10% to 15% more TAA than CON apples and 8% to 25% more TAA than INT apples. Across most parameters measured in this study, the CON and INT farm management systems were more similar to each other than either was to the ORG system. The production challenges associated with low-input organic apple farming systems are discussed. Despite limited technologies and products for organic apple production, the ORG apples in our study showed improvements in some fruit quality attributes that could aid their marketability.

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Gregory M. Peck, Ian A. Merwin, Christopher B. Watkins, Kathryn W. Chapman, and Olga I. Padilla-Zakour

Maturity and quality of fruit harvested from an orchard of disease-resistant ‘Liberty’ apple (Malus ×domestica Borkh.) trees was investigated during and after the transition from conventional to integrated (IFP) and organic fruit production (OFP) systems. Over 4 years, internal ethylene concentration, starch pattern index, flesh firmness, soluble solids concentration (SSC), titratable acidity (TA), and percent of surface blush of fruit at harvest were not consistently different between fruit from IFP and OFP systems. Total phenolic content and antioxidant capacity of the fruit were also similar between treatments. IFP-grown fruit contained more potassium during the first 2 years and more calcium in all years than OFP-grown fruit. After fruit were stored in air at 0.5 °C for 9 weeks in 2007, OFP-grown apples were firmer and had higher SSC, TA, and SSC:TA ratios. In double-blind triangle taste tests, consumer panelists were able to discriminate between the fruit from each treatment, but in double-blind hedonic and intensity tests, panelists did not consistently rate one treatment more highly than the other. Overall, consumer panelists favorably rated internal quality of fruit grown under both IFP and OFP systems. In 2006, when weather and disease caused a high percentage of OFP-grown fruit to have cosmetic defects, the panelists rated the appearance of OFP-grown apples as less acceptable than the cleaner-looking IFP-grown apples. Our study of ‘Liberty’ apple fruit maturity and quality during a 4-year transition period from conventional to IFP and OFP systems showed that differences were small if present, whereas internal fruit quality was rarely different between systems.

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Brianna L. Ewing, Gregory M. Peck, Sihui Ma, Andrew P. Neilson, and Amanda C. Stewart

Hard cider production in the United States has increased dramatically during the past decade, but there is little information on how harvest and postharvest practices affect the chemistry of the resulting cider, including concentrations of organoleptically important flavanols. For 2 years we assessed fruit, juice, and cider from a total of five apple (Malus ×domestica Borkh.) cultivars in two experiments: sequential harvests and postharvest storage. Different cultivars were used in 2015 and 2016 with the exception of ‘Dabinett’, which was assessed in both years. There were no differences in polyphenol concentrations in cider made from fruit that was harvested on three separate occasions over a 4-week period in either 2015 or 2016. Fruit storage durations and temperatures had little influence on the chemistry when the experiment was conducted in 2015, but polyphenol concentration was greater after storage in the 2016 experiment. In 2016, total polyphenols in ‘Dabinett’ ciders were 51% greater after short-term storage at 10 °C and 67% greater after long-term storage at 1 °C than the control, which was not subjected to a storage treatment. In 2016, total polyphenols in ‘Binet Rouge’ ciders were 67% greater after short-term storage at 10 °C and 94% greater after long-term storage at 1 °C than the control. Although results varied among cultivars and harvest years, storing apples for longer periods of time and at warmer temperatures may be a strategy to increase polyphenol, particularly flavanol, concentrations in hard cider.

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Candace N. DeLong, Keith S. Yoder, Leon Combs, Richard E. Veilleux, and Gregory M. Peck

A greater understanding of apple (Malus ×domestica) pollen tube growth rates can improve crop load management in commercial orchards. Specifically, applications of caustic bloom-thinning chemicals need to occur when enough, but not too many, flowers have been fertilized to achieve crop load densities that balance yields with marketable fruit sizes. In this study, the pollen tube growth rates of five crabapple (Malus sp.) cultivars were measured in the styles of three maternal cultivars at 12, 18, 24, and 30 °C after 24 hours in a growth chamber. Pollen tube growth rates were greatest for ‘Selkirk’ and ‘Thunderchild’ at 12 °C, and greatest for ‘Indian Summer’, ‘Selkirk’, and ‘Thunderchild’ at 24 °C. Pollen tube growth increased with increasing temperatures until 24 °C. There were minimal pollen tube growth rate increases between 24 and 30 °C. Overall, ‘Snowdrift’ had the slowest pollen tube growth rate of the five evaluated crabapple genotypes. At 24 and 30 °C, ‘Indian Summer’ and ‘Thunderchild’ pollen tubes reached the base of the style most frequently, and ‘Snowdrift’ pollen tubes the least frequently. Pollen tube growth rate was also influenced by the maternal cultivar, with Golden Delicious having relatively faster pollen tube growth than Fuji at 24 and 30 °C. Interactions among paternal and maternal genotypes as well as temperature after pollination reveal complex biological and environmental relationships that can be used to develop more precise crop load management strategies for apple orchards.

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Adam D. Karl, Michael G. Brown, Sihui Ma, Ann Sandbrook, Amanda C. Stewart, Lailiang Cheng, Anna Katharine Mansfield, and Gregory M. Peck

The recent growth in the U.S. hard-cider industry has increased the demand for cider apples (Malus ×domestica Borkh.), but little is known about how to manage orchard soil fertility best to optimize horticultural performance and juice characteristics for these cultivars. To assess whether nitrogen fertilizer applied to the soil can improve apple juice and cider quality, calcium nitrate (CaNO3) fertilizer was applied at different rates to the soil beneath ‘Golden Russet’ and ‘Medaille d’Or’ trees over the course of three growing seasons. The experiment started when the trees were in their second leaf. The trees were cropped in their third and fourth leaf. At the end of the first growing season of the experiment, the greatest fertilizer rate increased tree trunk cross-sectional area (TCSA) by 82% relative to the control, but this difference did not persist through to the end of the study. Yield and crop load were unaffected by the nitrogen fertilization treatments. Increasing the nitrogen fertilizer rate correlated positively with more advanced harvest maturity in ‘Golden Russet’ fruit, which resulted in greater soluble solid concentration (SSC). Fruit from the greatest fertilizer rate treatment had an average starch pattern index (SPI) that was 1 U greater than in the control, and an SSC that was 3% greater than the control. The fertilizer treatments did not affect juice pH, titratable acidity (TA), or total polyphenol concentrations. Yeast assimilable nitrogen (YAN) concentrations were increased by nitrogen fertilization for both cultivars in both harvest years. The greatest fertilizer treatment increased juice primary amino nitrogen by 103% relative to the control. Greater nitrogen fertilization rates correlated positively with less hydrogen sulfide production during the fermentation of ‘Golden Russet’ juice from the first, but not the second, harvest. During the first year, cumulative hydrogen sulfide production for the ‘Golden Russet’ control treatment was 29.6 μg·L–1 compared with the ‘Golden Russet’ high treatment, which cumulatively produced 0.1 μg·L–1. Greater maximum fermentation rates and shorter fermentation durations correlated positively with increased fertilization rate for both cultivars after the second harvest. High treatment fermentations had maximum fermentation rates 110% greater, and fermentation durations 30% shorter than the control. Other horticultural and juice-quality parameters were not affected negatively by the CaNO3 treatments. In orchards producing apples specifically for the hard-cider industry, nitrogen fertilizer could increase juice YAN, thus reducing the need for exogenous additions during cider production.