N balance as an indicator of N leaching in an oilseed rape – winter wheat – winter barley rotation

Abstract

Abstract The nitrogen (N) balance (N input − N export by the grain) is often used to estimate the risk of N leaching from arable land. In a nine year study during the leaching seasons 1991/1992 to 1999/2000, the relationships between N fertilization, N balance and N leaching in the subsequent percolation period were investigated in a multifactorial field experiment near Kiel in NW Germany at the Hohenschulen Experimental Station. The crop rotation was oilseed rape (OSR) – winter wheat – winter barley, while soil tillage (minimum tillage without ploughing, conventional tillage), application of pig slurry (none, application in autumn, application in spring, application in autumn plus in spring), mineral N fertilization (none, 120 or 240 kg N ha−1 to cereals), and application of fungicides (none, intensive) were all varied. In each year the rotation and the treatments were located on the same plots. N leaching was calculated by multiplying the drainage volume with the respective N concentration obtained using ceramic suction cups. In all crops, N fertilization significantly increased the N balance in the order mineral N