Reducing nutrient losses on dairy farms in The Netherlands

In the European Union, nutrient management is a topic of major political in terest. The goal for nitrogen (N) is that groundwater should contain less t han 50 mg nitrate/l. The general approach might result in a maximum amount of N or in a maximum number of cattle allowed per ha. However, individual c ountries develop alternative routes and take additional measures to deal wi th nutrient losses. In The Netherlands, ammonia volatilization (emission) s hould be reduced by 50-70% in the year 2000 compared with 1980, in addition to the European guideline for nitrate. Emphasis is placed both on phosphor us (P) and on nitrogen. Regulations limit the amount of manure (expressed i n P) applied per ha. A manure (P) quotum has been allocated to each farm. A more balanced P-supply to the land has been achieved by transport of manur e from surplus to deficit areas. Also lower P-contents of the concentrate f eeds are stimulated. N-losses can mainly be reduced by adapting the farm op eration. In this context several management practices were studied with a d airy-farm-simulation-model. A combination of a more efficient use of fertil izer N and restricted grazing in combination with a more balanced ration, r esulted in considerable reductions in nitrate leaching. Application of slur ry by injection techniques diminishes the ammonia volatilization at farm-le vel by almost 50%. Other low emission techniques, such as low emission hous ing and covering of slurry storages, have relatively high costs. In practic e, slurry application by injection and covering of slurry storages have bec ome obligatory. As a side effect, the odour of manure is largely eliminated from the environment as well. Application of manure to the land is only al lowed in the growing season. From 1998 on, dairy farmers have to keep recor ds of the nutrients on a nutrient balance sheet. On the basis of the nutrie nt balance a tax will be imposed on surplusses of N and P (C) 1999 Publishe d by Elsevier Science B.V. All rights reserved.