Effects of ageing and cultivation of grassland on soil nitrogen

Nitrogen losses from agriculture in the Netherlands have to be strongly decreased because of national and international policy (e.g. Nitrate Directive). The cultivation of grassland when grassland is renewed or converted into arable land may enhance net nitrogen mineralization and, thereby, nitrogen losses via leaching and denitrification. These nitrogen losses can be decreased by adjustment of management, but a good insight into the soil processes during ageing and after cultivation of grassland is required. A literature study was carried out to quantify the effects of ageing and cultivation of grassland on nitrogen losses from the soil. The study shows that the risk on losses increases when grassland age increases, the period between cultivation and reseeding increases and the nitrogen uptake capacity of the next crop decreases. In the Netherlands, only a few studies have been carried out and, especially, a quantification of the effects of cultivation on nitrogen losses under Dutch conditions is lacking. It is recommended to set up integral field studies in which both the agricultural and environmental effects of grassland cultivation are quantified. The results must be used to develop measures and tools to achieve environmentally and agriculturally sound systems of permanent and temporal grasslands