INTENSIFICATION OF GRASSLAND-BASED DAIRY PRODUCTION AND ITS IMPACTS ON LAND,NITROGEN AND PHOSPHORUS USE EFFICIENCIES

? Monitoring data of>5000 dairy farms collected and examined in uniform manner. ? Environmental performances of farms influenced by government regulations. ? N and P surpluses at farm level remained about constant with intensity level. ? N and P use efficiencies at farm, herd and soil increased with intensity level. ? Accounting for externalization of off-farm feed production affects NUE and PUE. ? Ammonia emissions per kg milk decreased with the level of intensification. Many grassland-based dairy farms are intensifying production, i.e., produce more milk per ha of land in response to the increasing demand for milk (by about 2% per year) in a globalized market. However, intensive dairy farming has been implicated for its resources use, ammonia and greenhouse gas emissions, and eutrophication impacts. This paper addresses the question of how the intensity of dairy production relates to N and P surpluses and use efficiencies on farms subjected to agri-environmental regulations. Detailed monitoring data were analyzed from 2858 grassland-based dairy farms in The Netherlands for the year 2015. The farms produced on average 925 Mg·yr^?1 milk. Milk production per ha ranged from<10 to>30 Mg·ha^?1·yr^?1. Purchased feed and manure export strongly increased with the level of intensification. Surpluses of N and P at farm level remained constant and ammonia emissions per kg milk decreased with the level of intensification. In conclusion, N and P surpluses did not differ much among dairy farms greatly differing in intensity due to legal N and P application limits and obligatory export of manure surpluses to other farms. Further, N and P use efficiencies also did not differ among dairy farms differing in intensity provided the externalization of feed production was accounted for. This paper provides lessons for proper monitoring and control of N and P cycling in dairy farming.