Disponibilidade e mineralização do nitrogênio após aplicações sucessivas de lodo de esgoto no solo, estimadas por meio de incubação anaeróbica

Abstract

The objective of this work was to evaluate, through anaerobic incubation, N mineralization and availability in soils treated with successive applications of sewage sludge, and to determine the residual effect of previous applications on nitrogen mineralization rate (NMR). Two long-term experiments were conducted with annual sewage sludge doses for corn cultivation: one with the recommended dose of sewage sludge, correspondent to 120kg ha -1 N, and 2, 4, and 8 times the dose in area at Embrapa Meio Ambiente, in Jaguariúna, in the state of São Paulo, Brazil; and the other with 80kg ha -1 mineral N fertilization, and 1 and 2 times the recommended dose of sewage sludge in area at Instituto Agronômico, in Campinas, in the state of São Paulo, Brazil; besides a control, without sewage sludge application. N availability and NMR were determined in field conditions and through anaerobic incubations in laboratory. Total nitrogen absorbed by plants was also estimated. Sewage sludge is more effective in supplying nitrogen to corn in the long term than mineral fertilization. The residual effect of sewage sludge does not influence the NMR from newly-added sludge. The method of anaerobic incubation is efficient in estimating the mineralization of N from newly-added sewage sludge.