Absorção de N, P, K, Ca, Mg e S pelo arroz irrigado influenciada pela adubação nitrogenada

Abstract

Taking in account that, there is no available method to adequately evaluate the soil nitrogen availability for plants, there is no way to trace calibration curve for this element, therefore, there is a research needs to establish answer curves in relation to nitrogen rates, as well as, to evaluate different cultivar responses. One experiment in greenhouse conditions was conducted at Soil Science Department of the Federal University of Lavras to evaluate the nitrogen rate effects on grain yield and to estimate the macronutrients (N, P, K, Ca, Mg and S) absorption and exportation by three irrigated rice cultivars. A completely randomized design with four replicates in factorial arrangement (5 by 3) using 3 irrigated rice cultivars, (Capivari, Inca e Sapucaí) and 5 nitrogen rates (O, 1OO, 2OO, 4OO e 8OO mg of N. kg-1 of soil) as factors were used. Nitrogen rates, in urea form, were applied in three times at 10, 30 and 50 days after emerging using 30%, 30% and 40% of the total rate, respectively. Capivari presented greater nitrogen absorption than Inca and Sapucaí rice cultivars. Differential grain yield rate responses were presented by cultivars, and 800 mg of N. kg-1 of soil was not enough for Capivari to reach its maximum yield. Capivari rice cultivar had the greatest yield among all cultivars, suggesting it is more efficient in nitrogen utilization, while the Sapucaí was the lesser efficient in nitrogen use.