Nitrogen balances as a tool to decrease nitrogen surpluses on dairy farms

Abstract

138 nitrogen (N) balances from dairy farms in southern Sweden were analysed. The balances were calculated using the farm gate method. N balances of the whole farm are a comparison of the farm's inputs and outputs. Amounts of purchased mineral fertilizer, purchased fodder and purchased concentrate are recorded in the accounts as well as data on milk sold, live animals sold or animals slaughtered and vegetable products sold. The investigation included N balances from three consecutive years, 1997,1998 and 1999.The N efficiency was improved and the N surplus per hectare was decreased in the second and third years of the study relative to the first year. The main reason for this was a lower fertiliser rate of N. However, there was a tendency on farms with a low N surplus in the first year to increase the fertiliser rate of N in subsequent years. The input of N from purchased feed did not change during the study period.