Soil organic matter fractions affected by N-fertilizer in a green cane management in Brazilian Coastal Tableland

ABSTRACT The recent approach of eliminating the use of fire for sugarcane harvesting (green cane) resulted in managing the crop on a trash-blanketed soil, which changed the content and dynamic of carbon and the nitrogen requirement. These alterations are relevant due to economic and environmental aspects of sugarcane production systems. This study aimed to evaluate changes in total organic carbon (TOC), total nitrogen (TN) and soil organic matter fractions with the application of N-fertilizer on the residues of green cane. The experiment was with sugarcane at the fourth ratoon in Linhares, Espírito Santo State, Brazil. The soil is a Xanthic Dystrudults, originated from Barreiras Group sediments in the coastal tableland region. The treatments were set in a completely randomized blocks experimental design and consisted of N (as ammonium sulphate) dosages varying from 80 to 160 kg N.ha–1 and the control. The application of increasing N doses resulted in accumulation of TOC and carbon in the humic, granulometric and oxidizable fractions of soil organic matter (SOM). It was obtained a model adjustment for quadratic regression for TOC, NT and SOM fractions. The doses between 80 and 100 kg N.ha–1 were the most favorable to accumulate carbon and the SOM fractions. N doses higher than 100 kg N.ha–1 favored SOM mineralization. The SOM fractions were responsive to application of N-fertilizer on harvesting residues of the green cane management area