mineralização e desnitrificação do nitrogênio no solo sob sistema plantio direto

Abstract

The knowledge of N dynamics in soil can facilitate the decision about crop rotation and the fertilizer application to the crops. The objective of this study was to quantify the soil N-stocks, inorganic-N and changes in the net mineralization and denitrification in a soil under no-tillage (NT). The experiment was set up at Santa Branca Farm in Tibagi (Paraná State, Brazil), on a clayey Oxisoil (Typic Hapludox) and was carried out from September 2000 to October 2001. The treatments were applied in non-random strips with split plots: no-tillage during 12 and 22 years with corn/wheat and soybean/wheat succession. Quantity of inorganic-N and the net mineralization and nitrification were higher under 22-years of adoption in relation to the 12-year-old NT. The crop succession used did not affect the average net mineralization and net nitrification. The N2O emissions were 25% higher in corn/wheat crop succession in relation to the soybean/wheat. Increasing time of no-tillage adoption increased the soil N stock, inorganic-N and net mineralization in the soil but the different years of adoption of NT did not lead to changes in N2O emissions.