Consórcio milho com Brachiaria brizantha cv. Marandu e fontes de nitrogênio nas frações da matéria orgânica do solo em sistema plantio direto

Abstract

Organic matter has been used as an indicator of soil quality, considering its influence in other important soil attributes to perform its duties. In order to investigate the potential of this indicator in evaluating management systems, we used a long-term experiment in an Oxisol in the Midwest region of Brazil. Because of this, the objective was to determine the effect of the combination corn intercropping / Brachiaria brizantha cv Marandu under no-tillage system and different sources of N in soil organic matter in the soil. The treatments were arranged in a factorial 2 x 4, two factors studied, the type of cultivation (with or without Brachiaria brizantha cv. Marandu.); and sources of nitrogen (without nitrogen, urea, urea + ammonium sulfate and ammonium sulfate) in a randomized block design with four replications. The work was carried out from 2005 to 2013, totaling eight years of second-crop corn and soybean in spring/summer season in the experimental area of the MS Foundation, located in the city of Maracaju - MS, but the collection of soil was carried out only in the last year after the corn harvest in autumn / winter 2013. Soil Samples were collected by means of trench, collecting soil at four depths (0-5 cm, 5-10 cm, 10-20 cm and 20-40 cm) and were determined the levels of total and labile organic carbon, total and labile nitrogen, content of particulate organic carbon and mineral fraction and light organic matter in water. Corn in intecropping with B. brizantha cv. Marandu increased the availability of total organic carbon, labile carbon and total nitrogen. The ammonium sulfate + urea increased the availability of total organic carbon in 0-5 cm depth, but this levels decreased in 20-40 cm dept. The ammonium sulfate increased the availability of mineral organic carbon at all depths. The urea increased the availability of total nitrogen in 0-5 cm depth, but this levels decreased in the labile nitrogen. The highest levels of total organic carbon, labile carbon, particulate organic carbon, total nitrogen and labile were observed in the 0-5 and 5-10 cm depths.