CHEMICAL PROPERTIES OF AN OXISOL UNDER NO-TILLAGE SYSTEM AS AFFECTED BY SOIL MANAGEMENT AND CROP ROTATION

The aim of this study was to determine the effects of soil management systems in no-tillage system (NTS) and crop rotations and on soil chemical properties. The experiment was conducted for six consecutive years, during which were made 12 crops (summer and winter). The experimental design was completely randomized in a split plot scheme. Treatments included four soil management (plots): P-1 = NTS followed annually for a plowing in the winter; P2 = NTS followed biennially for a plowing in the winter; P3 = NTS followed every three years for a plowing and P4 = continuous NTS. Subplots were crop rotation with crops in the summer and winter: R-1 = millet-common bean-millet-common bean-rice-common bean-milletcommon bean-millet-common bean-rice-common bean; R-2 = Soybean-common bean-soybean-wheat-rice-soybean-common bean-soybean-wheat-rice-common bean; R-3 = corn-common bean-corn-tomato-rice-common bean-corn-common bean-corn-tomato-rice-common bean; R-4 = millet-soybean-common bean-rice-common bean-millet-soybean-common bean-rice-common bean; R-5 = millet-common bean-corn-common bean-rice-common bean-millet-common bean-corn-common bean-rice-common bean; R-6 = Soybean-common bean-corn -common bean-rice-soybean-corn-common bean-rice-common bean. Each rotation cycle of three years crop season was repeated twice. Systems of soil management and crop rotations significantly affected soil chemical properties. The chemical attributes Ca, Mg, organic matter, P, K, Mn and Zn concentrated in the topsoil regardless of the crop rotation used in the managements of less soil disturbance. The pH values were similar during the 12 seasons in six years. The crop rotations used in different soil managements under NTS provided the improvement of soil fertility with values of organic matter, P, K, Cu, Mn and Zn contents equal to or higher than the initial values.