THE NITROGEN-BALANCE ON INTENSIVE DUTCH DAIRY FARMS - A REVIEW

Recently the governments in the Netherlands and some other Western European countries have set a number of targets to reduce nitrogen losses from agriculture to the environment in near future. The nitrogen balance of a farm shows the difference between N-input and N-output. The N-surplus is a potential source for loss to the environment. At present only about 14% of the N-input is recovered in milk and meat on intensive dairy farms in the Netherlands. High losses of nutrients occur during the conversion of grass, roughage and concentrates to dairy products, with animal manure as a by-product. Only a low percentage of the nitrogen from the animal manure is utilized. Different techniques, such as slurry handling and application and adaptation of nutrition, are available to reduce the N-losses. By optimizing these different techniques into an integrated system it is possible to reduce substantially the N-losses by better management of feeding and manuring. Farm scale studies describe reductions of N-surplus by 25 to 50% within a couple of years. Estimations indicate that with an optimized package of measures a further reduction of the N-surplus might be possible.