Farm gate level nitrogen balance and use efficiency changes post implementation of the EU Nitrates Directive

Farm gate nitrogen (N) balance and use efficiency was estimated across 150 specialist Irish dairy farms over a 7 year period between 2006 and 2012 using nationally representative data. The study period coincided with the introduction of EU Nitrates Directive regulations aimed at minimising losses of N to the aquatic environment and results indicated that N balance declined by 25.1 kg ha(-1) from 180.4 to 155.3 kg ha(-1) over the study period. This decline can almost entirely be attributed to reduced chemical N fertiliser inputs of 23.1 kg ha(-1) over the period, equivalent to 1247 kg N, or a cost saving of a,not sign1347 per annum across the average dairy farm. Nitrogen use efficiency also increased by 2.1 % points over the period from 20.8 to 22.9 %. This was achieved while increasing milk solids output from 405.3 to 449.6 kg ha(-1) in the context of a declining stocking rate (1.86-1.84 livestock units ha(-1)). These results suggest some positive impact of the regulations on N management on Irish dairy farms at the nutrient source end of the nutrient transfer continuum. This increased N management efficiency has a potential double dividend effect of increased returns to agricultural production while reducing the risk of N transfer to the aquatic environment. In addition to the introduction of the regulations, results of a random effects panel data model indicated that N balance and use efficiency are significantly influenced by factors such as fertiliser prices, stocking rates, land use potential, contact with extension services and climatic variables.