Estabilidade de agregados em solo cultivado com capim-Tifton 85 sob irrigação e formas de suprimento de nitrogênio

Abstract

Among the different strategies for recovering soil structural quality, we highlight the use of Tifton 85 grass (Cynodon sp.), which has a dense root system associated with organic fertilization. The aim of this work was to evaluate the stability of the soil structure in rotational grazing area of Tifton 85, as a function of the application of organic fertilizer and irrigation, in order to investigate if there is an increase in the soil physical quality. The treatments consisted in different forms of N supply, tested in irrigated and dry environment in Prudente de Morais (MG): 400 Kg/ha of urea (T1); 400 Kg/ha of bovine manure (T2); 400 Kg/ha of urea and manure, in the proportion 1:1 (T3) and the control, without nitrogen fertilization (T4). The following soil aggregation attributes were determined in layers 0-5 and 5-10 cm: mean weightdiameter (MWD), geometric mean diameter (GMD), stability index of aggregates of class <0,25 mm (SIA) and flocculation index (IF). Granulometric and organic carbon analysis were performed on the same layers. MWD, GMD and SIA did not differ among treatments, but were higher with irrigation use. For IF there was no statistical difference. The N form for fertilization of Tifton 85 grass was little determinant to soil structure stability in the evaluated time, but irrigation use favors aggregation attributes.