Nitrogen derived from fertilization and straw for plant cane nutrition

Abstract

The objective of this work was to evaluate the recovery, by plant cane, of the nitrogen (¹⁵N) from urea and from sugarcane (Saccharum spp.) crop residues – straw and root system – incorporated into the soil. The experiment was settled in 2005/2006 with the sugarcane cultivar SP81 3250. At planting, microplots of 2 m length and 1.5 m width were installed, and N applications were done with 80 kg ha^-1 N (urea with 5.05% in ¹⁵N atoms) and 14 Mg ha^-1 crop residues – 9 Mg ha^-1 of sugarcane straw (SS) and 5 Mg ha^-1 of root system (RS), labeled with ¹⁵N (1.07 and 0.81% in ¹⁵N atoms, respectively). The total N accumulation by plants was determined during the crop cycle. Although the N use by shoot from crop residue mineralization (PA and SR) increased significantly over time, this source hardly contributed to crop nutrition. The recovery of the ¹⁵N-urea, ¹⁵N-SS and ¹⁵N-RS by plant cane was 30.3±3.7%, 13.9±4.5% and 6.4±0.9%, respectively, representing 15.9, 4.7 and 1.4% of total nitrogen uptake by shoot.