Abstract

In sweet cherries, accumulated nitrogen (N) stores from the previous fall support early spring growth. To complement the N supply in the soil, Chilean growers use foliar urea applications after harvest. Information on the effectiveness of foliar N applications in sweet cherry is lacking. To study the canopy distribution of N applied as urea foliar sprays, an experiment using a Bing/Gisela (R) 6 (GI (R) 6) sweet cherry orchard was carried out in 2009/2010 in Chile (35 degrees 09' 53 '' S, 71 degrees 20' 43 '' W). The objective was to investigate N distribution and recycling in 3-year-old fruiting branches. A total of 120 branches (one per tree) were labeled using N-15-urea. N-15-urea was applied to the whole branch on four separate dates or treatments (TR) after fruit harvest: TR1=Jan, TR2=Feb, TR3=Mar and TR4=Apr. For each TR, a group of N-15-labeled branches (10 replications) was destructively harvested at 3 times/stages: 15 days after the urea foliar application (DAA), dormancy and stage I of fruit development. Branches were divided into the various organs, dried (70 degrees C), ground and processed for GC-MS analysis. In all TR, labeled urea was taken up by the leaves and translocated to various organs. The highest N levels were observed in the fruiting section. TR1 exhibited the highest N use efficiency (NUE%). Buds and bark showed the highest N derived from fertilizer (NDDF%) values. In all TR, stored N was recovered in the flowers, immature fruits and young leaves during the following spring. According to the results, urea sprays after fruit harvest constitute an alternative to complementing the N supply in the soil in sweet cherry trees using GI (R) 6.