Can We Approach Complete Dependence on Foliar-applied Urea Nitrogen in an Early-maturing Peach?

Abstract

The suspected contributory role of soil fertilization to nitrate pollution of groundwater has encouraged exploration of novel fertilizer management strategies. Foliar-applied urea has long been used to supplement soil N applications, but there have been no apparent attempts to replace soil N applications completely in deciduous orchard culture. Two experiments were conducted to study the effect of foliar-applied low biuret urea on productivity and fruit growth of the early maturing peach [Prunus persica L. Batsch (Peach Group)] cultivar, Early Maycrest. In a 3-year experiment, a total foliar urea regime was compared to an equivalent amount of N applied to the soil. The foliar treatment supplied adequate amounts of N to the various organs of the tree including the roots, shoots, and fruit buds, but mean fruit weights were lower than in the soil-fertilized treatment. In a 2-year experiment, a 50%-50% combination treatment of soil-applied N in late summer with foliar-applied N in October, maintained yields and fruit weight equal to the soil-fertilized control. Some soil-applied N appears necessary for optimum fruit growth. Soil N application may be needed to support root proliferation and associated processes, but we did not determine a threshold amount of soil-applied N needed. The combination treatment also reduced excessive vegetative growth which is characteristic of early maturing peach cultivars. Therefore, this combination treatment offers promise as a viable commercial practice for maintaining tree productivity and controlling excessive vegetative growth in peach trees.