The Leaching Potential and Recovery of 15-N-Fertilizer by Sugarcane Cultivated in Sandy Soil

Abstract

Leaching is an important loss pathway that limits N-fertilizer recovery by sugarcane. Our study evaluated the potential for leaching and recovery of ¹⁵N-fertilizer by sugarcane cultivated in sandy soil. Three nitrogen fertilization management strategies were tested: single dose (80 kg ha⁻¹), split (40 kg ha⁻¹ + 40 kg ha⁻¹) and supplementation (80 kg ha⁻¹ + 40 kg ha⁻¹), one more control; without nitrogen (N). Ammonium nitrate (AN) and ammonium sulphate (AS) were the sources N used. Leaching was determined by the N-mineral concentration (NH₄⁺, NO₂⁻ and NO₃⁻) and ¹⁵N-fertilizer in the soil solution at a depth of 0.7 m. Nitrogen recovery was quantified using ¹⁵N-fertilizer in the sugarcane shoots. Significant leaching occurred in the first 60 days after fertilization (DAF), but splitting the fertilization reduced N-mineral leaching by 50%. During this period, 78% of the nitrogen in the leachate originated from the fertilizer (NDFF_(L)). The contribution of nitrogen fertilization was highest in the first 30 DAF, where the fertilizer accounted for 39% of the nitrogen absorbed by sugarcane. But the plant’s nitrogen recovery (R) was limited to only 4% of the applied nitrogen. At harvest, the R of ¹⁵N-fertilizer by sugarcane was less than 20%. Splitting or applying a single dose of fertilizer did not improve nitrogen recovery at the end of the cycle. Our study showed that the leaching and recovery of ¹⁵N-fertilizer were found to be proportional to the applied doses according to the management strategies and nitrogen sources compensated for nitrogen leaching throughout the cycle.