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James M. Wargo, Ian A. Merwin, and Christopher B. Watkins

`GoldRush' is a new scab (Venturia inaequalis) resistant apple (Malus ×domestica) with excellent flavor and storage qualities that tends to produce small and russeted fruit. We investigated the effects of rate, timing, and method of nitrogen (N) fertilizers on `GoldRush' fruit size and quality during 1998-99. Fertilizer treatments were 1) no N fertilizer (control); 2) a low N rate of 45 kg·ha-1 (40.1 lb/acre) applied in April (LN-Apr); 3) a low N rate of 45 kg·ha-1 applied half in April and half in June (LN-Apr+Jun); 4) a high N rate of 90 kg·ha-1 (80.3 lb/acre) split in April and June (HN-Apr+Jun); 5) a high N rate of 90 kg·ha-1 applied in April, May, June, and July at 22.5 kg·ha-1 (20 lb/acre) each month (HN-Apr+May+Jun+Jul); and 6) canopy sprays of 1% (wt/wt) urea-N, equivalent to 7 kg·ha-1 (6.2 lb/acre) applied monthly in May, June, July, and August (foliar urea). In 1998, an additional foliar urea spray at 5% (wt/wt) concentration was applied to trees after harvest. The first year's Ntreatments did not affect relative average fruit weights or total yields, but unfertilized trees produced more fruit in smaller size categories. Nitrogen fertilization resulted in greener and softer fruit both years. In the second year, all N additions increased yields compared with controls, but average fruit weight was inversely correlated with crop load. Foliar urea sprays and HN-Apr+May+Jun+Jul treatments increased yields the most. Fruit from LN-fertilized trees were normally distributed across a range of eight box-count size categories, peaking at size 100 both years. In the unfertilized control, fruit size was skewed into smaller size categories and yield was reduced. Total yields were greatest in foliar urea and HN-Apr+May+Jun+Jul treatments, but fruit-size distribution was skewed into smaller categories, peaking at size 138 in the second year. Foliar urea and HN-Apr+May+Jun+Jul treatments produced the highest crop value, but when estimated labor and fertilizer costs were considered, foliar urea and LN-Apr+Jun were the most efficient treatments. Nitrogen fertilizer improved fruit size and market value, but average fruit size in all treatments remained relatively small in both years, indicating that N fertilization alone may not increase fruit size in `GoldRush.'

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James M. Wargo, Ian A. Merwin, and Christopher B. Watkins

`Jonagold' apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] often fail to develop adequate red coloration at maturity and become soft and greasy in storage. During two growing seasons, we tested factorial combinations of three preharvest treatments affecting `Jonagold' quality at harvest and after storage: 1) three nitrogen (N) treatments [36 kg·ha-1 soil applied N, 6.9 kg·ha-1 of urea-N (1% w/v) in foliar sprays mid-May and June, or no N fertilizers]; 2) trunk girdling in early August each year; and 3) foliar applications of aminoethoxyvinylglycine (AVG, formulated as ReTain) 3 weeks before the first scheduled harvest. Fruit were sampled at four weekly intervals each year and evaluated for maturity and quality at harvest and after storage. Foliar urea and soil-applied N delayed red color development in 1998 but not 1999, increased fruit size in girdled and nonAVG treated trees in both years, and increased greasiness in 1999 only. AVG reduced fruit greasiness after storage both years. Nitrogen uptake was reduced in the dry Summer 1999, but N treatments still increased poststorage flesh breakdown. Mid-summer trunk girdling increased red coloration and intensity both years and improved market-grade packout. This effect was not caused by advanced maturity, although trunk girdling slightly increased skin greasiness. Girdling reduced fruit size only on trees of low N status. The AVG applications delayed maturity and red color development by 7 to 10 days in both years compared with untreated fruit. In 1998, the combination of AVG and N fertilization delayed red color development more than either treatment alone. Fruit softening and greasiness were reduced in AVG-treated fruit harvested at the same time as untreated fruit, but this effect was not observed when AVG treated fruit were harvested at comparable maturity 7 to 10 days later. Trunk girdling and withholding N fertilizer were the best treatments for enhancing red coloration, and foliar N concentrations of ≈2.0% (W/W) resulted in better packouts compared with higher leaf N levels. AVG was an effective tool for delaying fruit maturity and maintaining fruit quality awaiting harvest, but not for improving red coloration of `Jonagold' apples.

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Esmaeil Fallahi, Denise Neilsen, Gerry H. Neilsen, Bahar Fallahi, and Bahman Shafii

. Neilsen D. 1994 Fertigation of fruit trees. The B.C. experience 191 199 Peterson A.B. Stevens R.G. Tree fruit nutrition Good Fruit Growers Yakima, WA O'Connell, M.G. Goodwin, I. 2007 Responses of ‘Pink Lady’ apple to deficit irrigation and partial root

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Esmaeil Fallahi

of fruit trees: The B.C. experience, p. 191–199. In: A.B. Peterson and R.G. Stevens (eds.). Tree fruit nutrition. Good Fruit Grower, Yakima, WA O′Connell, M.G. Goodwin, I. 2007 Responses of ‘Pink Lady’ apple to deficit irrigation and partial root zone

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Esmaeil Fallahi, Bahar Fallahi, and Bahman Shafii

, British Columbia Can. J. Soil Sci. 86 909 924 Neilsen, G.H. Parchomchuck, P. Neilsen, D. 1994 Fertigation of fruit trees: The B.C. experience, p. 191–199. In: Peterson, A.B. and R.G. Stevens (eds.). Tree fruit nutrition. Good Fruit Grower, Yakima, WA O

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Esmaeil Fallahi, Bahar Fallahi, and Michael J. Kiester

Fertigation of fruit trees: The B.C. experience, p. 191–199. In: A.B. Peterson and R.G. Stevens (eds.). Tree fruit nutrition. Good Fruit Grower, Yakima, WA O’Connell, M.G. Goodwin, I. 2007 Responses of ‘Pink Lady’ apple to deficit irrigation and partial root

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Dan TerAvest, Jeffrey L. Smith, Lynne Carpenter-Boggs, Lori Hoagland, David Granatstein, and John P. Reganold

. Growth J. Amer. Soc. Hort. Sci. 111 525 528 Stiles, W. 1994 Nitrogen management in the orchard 41 50 Peterson A.B. Stevens R.G. Tree fruit nutrition shortcourse proceedings Good Fruit Grower

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Dan TerAvest, Jeffrey L. Smith, Lynne Carpenter-Boggs, David Granatstein, Lori Hoagland, and John P. Reganold

fruit nutrition shortcourse proceedings Good Fruit Grower Yakima, WA Tabatabai, M.A. 1994 Soil enzymes 775 834 Mickelson S.H. Bigham J.M. Methods of soil analysis, part 2, microbiological and biochemical properties Soil Sci. Soc. Am Madison, WI TerAvest