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

Andrea Machmüller, Albert Sundrum


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.