Nitrate leaching following cultivation of contrasting temporary grassland.

The N-surplus in grazed grassland is much higher than in cut grassland. Therefore, the residual effects of three years of temporary grassland on nitrate leaching in the following cereal crop were determined. Grassland managements were either cut leys or grazing with dairy cows in both pure grass and grass-clover mixtures. The cows were fed two levels of N in the supplements. Grassland management had little effect on the subsequent nitrate leaching, which ranged from 6 to 36 kg N ha-1, even though the surplus after three years of grassland ranged from 36 to 984 kg N ha-1. This indicates that substantial losses occurred during the grassland period. Application of fertiliser-N to the cereals had a much larger effect on nitrate leaching. It is concluded that management in the first years following grassland cultivation is of considerable importance in reducing nitrate leaching losses.