Corretivos e correção do solo para pastagens no norte de Minas Gerais

Abstract

It was evaluated acidity correction practices on the soil chemical attributes of the 0-10 and 0-20 cm depth layers and about the nutrition and production of Urochloa brizantha cv. Marandu cultivated in irrigated and rainfed systems. The study was carried out in areas of Dystrophic Red Latosol in the North of Minas Gerais implanted under three different systems of management of soil acidity correction. System 1 consisted of the addition of 350 and 700 kg ha-1 of calcium and magnesium oxide estimated by the method of aluminum neutralization and elevation of magnesium calcium contents and by the method of saturation by bases, respectively. System 2 consisted of the addition of 1200 kg ha-1 of limestone and 750 kg ha-1 of calcium and magnesium oxide estimated by the method of aluminum neutralization and elevation of calcium and magnesium contents. System 3 was implanted in a non-irrigated area and irrigated by central pivot with application of 400 kg ha-1 of calcium and magnesium oxide estimated by the methods of aluminum neutralization and elevation of calcium and magnesium contents and of the saturation by bases. It was randomly collected soil, fodder and diagnostic leaf samples for analysis of chemical attributes, aerial dry mass production (MSPA) and nutrient content in the plant, respectively. The System 1 was evaluated after 1 year of correction of soil acidity. For systems 2 and 3 the evaluations occurred in the second year after the correction. For each variable, it was calculated the mean and the confidence interval estimated by Student's t test at 5% of probability. The MSPA production of the different systems were correlated with the nutrient contents in the reference leaf, and in the aerial part of the plants, as well as the MSPA and nutrient contents in the reference leaf, and in the aerial part of the plants were correlated with the soil chemical attributes, in the 0 to 10 layer and 0 to 20 cm in depth, by Pearson correlation at 5%. The contents of calcium and magnesium of the soil were higher in the areas where the dose of the corrective, calcium and magnesium oxide, was estimated by the method of saturation by bases when compared to the contents of the areas where the dose of the corrective was estimated by the aluminum neutralization method and elevation of Ca and Mg contents. During two years of cultivation, limestone kept the pH of the soil closer to neutrality, but the Mg contents were lower than those where Ca and Mg oxide were applied. In the irrigated pasture there was a higher production of forage dry mass and the values of pH, Ca and Mg were higher than in the rainfed area. The best correlations were obtained between the production of dry mass of forage with the nutrient contents in the soil layer of 0 to 20 cm depth and with the nutrient contents in the diagnostic leaf.