Nitrogen-mass flows and balances of dairy farms in the context of the German fertilizer ordinance

Abstract

The present study is based on extensive farm records regarding the annual N-turnover of 36 dairy farms. The following statements can be derived from the N-mass flows and balances calculated: Dairy farm N-mass flows and balances show a high variability. A farm-gate balance is to the detriment of a large proportion of dairy farms respectively forage-growing farms. Where fertilization of arable land is concerned, dairy farms respectively forage-growing farms operate just as well or as badly as cash crop farms. Apart from improving the farm N-efficiency, the level of the farm N-surplus needs to be continuously monitored. The level of the farm N-surplus is predominantly determined by the farm’s harvest yields and fertilization management. Given the current calculation methods, many of the farm N-surpluses and their inherent risks for the environment tend to be considerably underestimated.