Indoor breeding or full-grazing dairy management? A farm system analysis of Nitrogen Use Efficiency

This paper investigates nitrogen (N) balance and nitrogen use efficiency (NUE) as a function of grazing intensity on dairy farms in Northwest Germany. 30 farms were analyzed in four groups according to their pasture management systems. Based on the farm data, a substance flow analysis was carried out. Results show that the average annual N surplus tends to increase while NUE decreases from zero-grazing towards full grazing. Considerable differences were highlighted between the mandatory nutrient balances reported by farmers and the N balances calculated in this study.

Oversupply of nitrogen (N) fertilizers has led to various environmental problems, e.g. nitrate pollution in ground water (FAO, 2018). Political targets for improving water quality and reducing ammonia emissions have not been adequately accomplished in Germany as defined by the Nitrates and the National Emission Ceilings Directive and, thus, national legislation has been further tightened. The present study compares specialised dairy farms in Northwest Germany with different grazing intensities related to the N use efficiency (NUE) and identifies N mitigation potentials in livestock management.