Fish Hydrolysate Fertilizer Should Not 

 Be Applied Foliarly to Apple 



J. R. Schupp, M^ Schupp, and M.M. Bates 

 Highmoor Farm, University of Maine 



The four- tx) six-week period following bloom is a 

 critical time for crop development in apples. During 

 this period, the mfgority of seasonal vegetative 

 growth takes place, and firuit set, return bloom, 

 potential yield, and potential fruit size are deter- 

 mined. Mineral nutrient reserves become depleted, 

 as utilization is greater than root uptake, and nutri- 

 ents, especially nitrogen, can become a Umiting 

 factor to growlii, even though soil reserves are ad- 

 equate. 



Foliar sprays of mineral nutrients during this 

 critical period can be beneficial in supplementing 

 ground-applied fertilizers. These applications do 

 not replace the regular ground-applied fertilizer 

 program, they simply fill the gap during the time 

 that demand outstrips supply. Foliar nitrogen appli- 

 cations in particular have been shown to increase 

 fruit set and fruit size when applied at 8 to 12 lbs per 

 acre during this time. Previous studies have shown 

 that foliar urea sprays are a safe and effective 

 method for fertilizing apple (Stiles and Reid, 1991). 



Fish hydrolysates, a byproduct of the fishing 

 industry have recently been recommended as an 

 organic nitrogen fertilizer for cranberry 

 (DeMoranville, 1990), apple, and blueberry (Weis 

 and Bramlage, 1992). The fishing industry is inter- 

 ested in developing new uses for this material and in 



cooperation with the Portland (ME) Fish Exchange, 

 we investigated the feasibility of using fish hydroly- 

 sates as a foliar nitrogen source for apple. 



Mature Delicious/MM.lll and Golden Deli- 

 cious/MM. 106 apple trees, growing at the University 

 of Maine Highmoor Farm in Monmouth were used 

 for this experiment. "Gulf of Maine" fertilizer, con- 

 taining 2% N, 4% P, and 2% K was supplied by the 

 Portland Fish Exchange. 



Treatments were as follows: 



1. Control, no foliar fertilizer. 



2. Fish hydrolysate, 3 gallons in 25 gallons of 

 water. 



3. Urea, 1.25 lb in 25 gallons of water. 



Both fertilizer treatments, calculated to provide 

 the equivalent amount of nitrogen as an application 

 of 12 lb urea/acre, were applied as a dilute spray with 

 a handgun. Three applications, at petal fall (PF), 

 PF+7 days, and PF+14 days, were made on four 

 repUcations of each cultivar. 



Fish hydrolysate fertilizer reduced fruit set of 

 both cultivars (Table 1). Foliar urea increased fruit 

 set and yield of Golden Delicious but had no effect on 

 Delicious. Fruit from fish hydrolysate-treated 

 Golden Delicious trees had higher soluble solids 

 than those from urea-treated trees, and this appears 



Table 1. The effects of foliar sprays offish hydrolysate fertilizer and urea on fruit set, yield, fruit 

 soluble solids, and russeting of Delicious and Golden Delicious apple. 



Fruit set (%) 



Treatment 



Del. 



Gold. 



Yield (kg) 

 Del Gold. 



Soluble 

 solids (%) 



Russeting* 



Del. 



Gold. 



Del. 



Gold. 



Control 73 a" 19 b 81 ab 54 b 10.2 a 13.5 ab 1.3 b 1.8 b 



Fish hydrolysate 38b 7c 64b 21 b 10.2 a 14.1 a 3.7 a 4.1 a 



Urea 64 a 34 a 92 a 128 a 9.8 a 12.8 b 1.0 b 2.0 b 



• Russeting was rated on a scale of l=none to 5=100% russeted. 



" Means within columns not followed by the same letter are significantly different at odds of 19:1. 



Fruit Notes, Spring, 1993 



17 



