Farm gate nitrogen surpluses and nitrogen use efficiency of specialized dairy farms in Flanders: Evolution and future goals

Data from the Farm Accountancy Data Network revealed that from 1989 to 2001 the average farm-gate N surplus of Flemish specialized dairy farms decreased from 378 to 238 kg N ha−1, the corresponding whole-farm N efficiency increased from 15% to 22%. Study of European literature on dairy farming, of experimental farms or farm groups and of progressive Flemish farms showed that there is scope for further improvement of the N use efficiency in Flemish dairy farming. The improvement can mainly be realized by changes in the operational management, resulting in an ever decreasing use of fertilizer N and concentrate N. Reasonable targets for sustainable dairy farming in Flanders are 150 kg N ha−1 year−1 for the farm-gate N surplus and about 85 kg milk kg−1 N surplus for eco-efficiency. These targets can be reached at production levels of up to 10,000 à 12,000 l ha−1 and at a satisfying income per unit of labour.