Taxa de mineralização do nitrogênio de resíduos orgânicos

Abstract

The use of organic sources of N is an alternative in agricultural production systems. The knowledge of the mineralization rate of organic residues is a tool aiding the management of such fertilizers and in the prevention of possible environmental impacts. The objective of this study was to quantify the net mineralization rate of N in soil fertilized with different organic residues (ORs). Soil samples from the A horizon of a very clayey typical dystroferric Red Latosol collected at the 0-0.15 m depth were utilized. The treatments were: poultry litter (18 t ha-1 ); cattle manure (32 t ha-1 ); organic compost (35 t ha1 ); worm humus (47 t ha-1 ); residue from the manufacture of industrial gelatin (18 t ha-1 ), and the control (without organic residue addition). The applied rate of each residue was based on maize N requirement. The experiment was set up in plastic containers with perforated lids containing 200 g of soil and maintained in a dark ambient at room temperature. The experimental design was completely randomized with five replicates. The contents of N as nitrate and ammonium in the soil were measured at 7, 14, 28, 63, 113, 146, 181, and 209 days of incubation. Chicken manure presented the highest rate of mineralized N. Bovine manure and industrial gelatin residue presented N immobilization in the first 49 days of incubation. Therefore, the high variability in N mineralization rates of organic residues suggests great difficulty in synchronizing the periods of higher N from ORs release in soil to meet phases in which N is highly required by plants.