IMPACT OF CONVENTIONAL MANAGEMENT UPON BOTH PHYSICAL PROPERTIES AND HUMIC SUBSTANCES OF SOILS UNDER CERRADO

摘要

The utilization of intensive conventional management system on soils under cerrado biome has caused modification in their properties, as well as, in the behavior and quality of the organic matter. The objective of this research was to evaluate the impact of conventional soil management practices upon physical properties, contents and qualities of humic substances of a Red-Yellow Oxisol, formerly, under cerrado (savana-like) natural vegetation. The study was accomplished on an private agricultural property in the municipal district of São Desidério-BA. They were appraised four areas under different length of times of agricultural use and one area under native cerrado (savana-like). The length of time under agriculture use was one, two, three and six years, and after six years the studied area was left uncultivated for a period of three years. The soil has been prepared under traditional systems which consists of plowing the land twice with heavy disks followed by twice grading. It was also applied, during the seedling time, N-P-K fertilizer plus micronutrients and lime according to soil analysis. The areas have been cultivated with corn and soybeans in a rotation system. It was observed that the adopted management system was not sustainable, because, at the first three years under cultivation occurred a great deterioration of physical properties such as soil density, porosity and available water contents. The humification process and the quality of the organic matter were influenced by both utilization of lime and by the rotation system (corn/soybeans). The used system was more benefic for the process of stabilization of the humic substances than for the physical properties of the studied soils.