C and N stocks and maize yield under tillage systems and nitrogen fertilization at Red Yellow Latosol in the savanna of the Piaui State/Estoques de C e de N e produtividade do milho sob sistemas de preparo e adubacao nitrogenada em um Latossolo Vermelho-Amarelo do cerrado piauiense

Total soil organic carbon (C) and nitrogen (N) stocks and crop yield are influenced by tillage, biomass input from crop and nitrogen fertilization. This research aimed to evaluate the effect of different tillage systems associated to nitrogen doses on corn yield and C and N stocks in the Red Yellow Latosol in savanna of Piaui state, Brazil. The experiment was carried out in Baixa Grande do Ribeiro, south of Piaui state. The treatments were distributed in a randomized complete blocks and factor arrange 2x5, two tillage systems (no-tillage (NT) and conventional (CT)) and five nitrogen doses (0, 60, 120,180 and 240kg [ha.sup.-1] N), respectively, with six replications. The corn grain yield (GY) and C and N inputs were measured and C and N soil stocks were evaluated in the 0-5, 5-10, 10-20 and 20-40cm. N doses caused a quadratic response in the grain yield, C and N inputs from maize crop and soil C stocks in both tillage systems. Higher GY were obtained by 138 and 134kg N [ha.sup.-1] to CT and NT, respectively. Higher C and N inputs were obtained by 140 and 175kg N [ha.sup.-1], in the CT and by 139 and 100kg N [ha.sup.-1] in the NT system, respectively. Nitrogen fertilization increased soil C stocks in the NT comparing to CT in the 0-5 and 5-10 depths. No tillage adoption combined with balanced nitrogen fertilization can be important to soil organic matter production in soils under cerrado of Piaui state.