Base Saturation in Function Cover Crops and Residual Doses of Limestone and Nitrogen Fertilization in No-Tillage System.

In Brazil the no-tillage system is widely adopted throughout the territory, occupying 32 million hectares. The untilled soil in the system and the consequent accumulation of crop residues, correctives and fertilizers on surface, promote changes in the chemical characteristics of the soil. The objective of this experiment was to evaluate the behavior of base saturation in the soil due to cover crops (millet and Crotalaria juncea), residual doses of lime and nitrogen, eight years after  implantation no-tillage system. The experiment is being conducted in Selvíria, MS, Brazil (20º22'S, 51°22'W and 335 m of altitude) where the crop year 2000/01 was implemented tillage with soybean cultivation. In crop year 2001/02, it was installed modes of lime application (total dose or split in 2 or 3 times, with applications in surface) and annual cultivation of cover crops (Pennisetum americanum and Crotalaria juncea). In crop year 2003/04, it were subdivided plots for the installation of the treatments with annual doses of nitrogen (0, 90 and 180 kg/ha) and was replaced soybean by corn, evaluating the residual in 2004/05 and 2005/06. In 2006/07 agriculture it was evaluated the residual treatments in soybean crop and in 2007/08, it was held a reapplication of lime in surface at doses of 0, 812 and 1624 kg/ha. Thus the present work refers to the agricultural year 2008/09, which after soybean harvest, soil samples were collected at layers of 0.00-0.05, 0.05-0.10, 0.10 -0.20 and 0.20-0.40 m depth, to evaluate the values ​​of base saturation. After two years of liming, only the layer from 0.0 to 0.05 m, obtained a linear increase in the values ​​of V% according to doses lime used and the highest values ​​were obtained with millet crop.