Information about nutrient absorption of citrus orchards is important to establish guidelines for best soil fertility management. However, studies on the fate of applied N fertilizers and validation of nitrogen (N) dose recommendations are scarce in the literature. The present work evaluated (i) the accumulation of nutrients and the distribution of N (15N) applied to citrus orchard and (ii) validated the N fertilization rate applied to young bearing orange trees. Three- to four-year-old Pêra sweet orange trees Pera grafted on Rangpur lime were fertilized with 150, 300, 450, and 600 g of N per tree, as ammonium sulfate, split in three applications from spring to summer. A control treatment without N was included. In the same orchard, three plants were fertilized with 300 g per tree of N-[(15NH4)2SO 4)] labeled with 15N to study the fate of N in the soil-orange tree system. Fruit yield and recovery of 15N by tree biomass were evaluated. The efficiency of fertilization, estimate by tree N absorption, varied from 20 to 27% of the total applied N. Fruits exported 35% of the N taken up from fertilizer. Furthermore, the highest fruit yield was attained with N rate of 400 g/tree.
Citrus; isotope stable; mineral nutrition; nutrient distribution; ammonium sulfate
