Nitrogen (N) management in the 'De Marke' dairy farming system

In the sandy regions of The Netherlands, high losses of N from intensified dairy farms are threatening the environment. Therefore, government defined decreasing maximum levy-free N surplusses for the period 1998-2008. On most dairy farms, the current N surplus has to be reduced by half at least. Far mers fear that realizing these surplusses will be expensive, because it lim its application of animal manure, which then has to be exported or addition al land has to be bought. Moreover, farmers are worried about the impact on soil fertility. To explore the possibilities for reducing surplusses of av erage intensive farms by improved nutrient management, farming systems rese arch is carried out at prototype farm 'De Marke'. Results are compared with results of a commercial farm in the mid-1980s, the moment that systems res earch started and introduction of the milk quota system put a halt to furth er intensification. Results indicate that average intensive farms can reali se a reduction in N surplus to a level below the defined final maximum, wit hout the need to buy land or to export slurry. Inputs of N in purchased fee ds and fertilisers decreased by 56 and 78%, respectively. Important factors are reduced feed intake per unit milk, as a result of a higher milk yield per cow, less young stock and judicious feeding, an improved utilization of 'home-made' manure and a considered balance between the grassland and maiz e area. Changed soil fertility status did not constrain crop production. Ni trate concentration in the upper groundwater decreased from 200 to 50 mg l( -1), within a few years.