Foliar Urea Can Supplement Soil-applied Fertilizer in an Early Maturing Peach

Abstract

Despite early studies that suggested foliar urea was ineffective in supplying nitrogen to peach trees, recent studies have shown rapid uptake of low biuret urea by peach leaves and subsequent mobilization to perennial tree parts. Labeled nitrogen experiments have demonstrated the distribution of N among organs to be very similar whether the N is supplied from foliar urea or from soil-applied fertilizer. However, questions still remain concerning the long-term productivity of trees treated repeatedly with foliar urea. Our first experiment was conducted on an early ripening peach, which generally requires about 100 kg N/ha applied to the soil. The treatment to replace all soil applied N with two or three foliar applications of urea in the fall resulted in similar N distribution throughout the tree and equal vegetative growth. However, fruit size was consistently smaller than the soil-fertilized control over a 3-year period. Our second experiment, conducted on the same variety, imposed a treatment to supplement about half the soil applied fertilizer with fall foliar urea applications. This treatment was able to maintain fruit size and yield over a 2-year period. Furthermore, vegetative growth was reduced compared to the soil-fertilized control, suggesting foliar urea may be a useful tool to help manipulate the distribution of growth between reproductive and vegetative processes.