In the Netherlands there is a remarkable difference in environmental performance between the average commercial dairy farm and some experimental dairy farms. Despite 15 years of policies and measures to decrease nutrient losses, experimental dairy farms based on careful nutrient management, like 'De Marke', realize much higher resource use efficiencies and much lower nutrient surpluses than the average commercial dairy farm.This paper discusses the transitions that are needed to bridge the gap between experimental dairy farms and commercial pilot farms. In the project 'Cows & Opportunities', 17 farms were selected representing the full range of conditions for dairy farming, with emphasis on dry sandy soils because of their environmental constraints. There are intensive discussions and communications between farmers, extension services, advisers from the industry, researchers and policy makers. Firstly, all farms were thoroughly analysed in terms of agronomic and environmental performance in the original situation. Secondly, opportunities for improving their performance were analysed using sustainability criteria like nutrient losses, energy and water use, emission of greenhouse gases, crop protection, accumulation of heavy metals, and nature development. Thirdly, an outline for a farm development plan was formulated to meet the nitrogen and phosphorus surplus targets set by the Dutch government. These first outlines (designs) were thoroughly discussed between farmers and researchers. After modelling the farm design to calculate the environmental and economic effects, the farm development plan was adjusted wherever needed, approved and implemented. The performance of the farm will be monitored and evaluated over the next few years. In the original situation, the MINAS nitrogen surplus on the farms ranged from 47 to 349 kg ha-1 , with an average of 207 kg. The modelling results indicated an average N surplus of 131 kg ha-I after implementation of the farm development plans, Le., 19 kg ha-1 less than the target surplus. The project 'Cows & Opportunities' demonstrates that it is-po&sible to meet the nitrogen and phosphorus surplus targets by taking simple measures. The project yields useful information on the relations between management measures, constraints, nutrient balances and environmental performance.

Sandy soils in the Netherlands are mainly used for dairy farming. As a result of intensification of dairy farming in the recent past, valued functions of sandy regions now are threatened by high emissions of nitrogen (N) and phosphorus (P) and by increased water consumption by forage crops. Improved utilization efficiency of resources is proposed as a strategy to realise environmental targets in an economically viable way. Experimental results of the prototype system 'De Marke' indicate that an average intensive commercial farm can halve inputs of fertilizers and feeds at least, without the need to reduce milk yield/ha or to export slurry. Water consumption can be reduced by 13%, increasing groundwater 'production' by 570 msuperscript 3/ha. Nitrate concentration in the upper groundwater decreased from 200 to 50 mg/litre. Changes in soil fertility did not lead to serious agricultural problems but costs of milk production increased by 5%. However, additional costs may be compensated for if the extra groundwater is 'harvested' by water companies, because of high cost of purification of surface water and consumer preference for drinking groundwater instead of river-water. In 1999, the examined strategy of improved resource management was implemented on 12 commercial farms, representing the full range of conditions for dairy farming in the Netherlands.