Changing the Sugarcane N Credit and C Fluxes in Soil by the Application of N-Enhanced Efficiency Fertilizers

Abstract

The accumulation of sugarcane residues (ASR) on the soil surface in areas with mechanized harvest increases the soil quality with a direct effect on crop production. However, the ASR presents a high C:N (carbon: nitrogen) which promotes N immobilization. The application of N enhanced efficiency fertilizers (EFF) could be an alternative to increase the sugarcane N credit and C in the soil due to inputs in soil. Our goal here was to monitor the additions of EFF in soil and the influence in routes of C stabilization and N credit. A laboratory study was run with the association of urea/U, urea + sulfur/U + S, urea + copper + boron/U + CuB, or urea-kimcoat/U + Kc with sugarcane residue in the soil. Soil C (total organic carbon/TOC, humin/HU, humic acid/HA, and fulvic acid/FA), N (soil and residues) and CO2 emissions were monitored. Results showed that the application of U and U + CuB presented a higher CO2 emission, which created a negative balance in TOC and FA. The routes of C were increased in HA, while there was a decrease in FA. The credit N of fertilizers and sugarcane residue were positive, with an average of 90% and 86%, respectively. Using machine learning, the U + S and U + Kc presented a lower CO2 emission, if compared with the performance of U and U + CuB. Based on these results we conclude that the U and U + CuB presents a lower performance with higher C losses with reduction of carbon in soil.