Establishing national benchmarks of N and P balances and use efficiencies on Irish grassland farms

Improving grassland agriculture sustainability requires minimising nutrient balance (NB) surpluses and increasing nutrient use efficiencies (NUE). To set targets for improved farm nutrient management, benchmarks were established by farm sector and production intensity using 1,379 nationally representative farms from the Irish National Farm Survey. Annual farm-gate NBs (kg ha-1) and NUEs (%) for nitrogen (N) and phosphorus (P) were calculated from import/export data from 2008 to 2015, inclusive. Quantile regression analysis and percentile rankings were used to identify benchmark farms with the lowest surpluses per production intensity (kg N or P exported ha-1), highest NUEs and highest gross margins (Euro ha-1). Large differences in NBs between farms of the same sector and production intensity indicate considerable potential for improvements. For example, benchmark dairy farms maximised productivity (median export 55 kg N ha-1), NUE (median 31%) and gross margins (median Euro 2,593 ha-1) whilst keeping surpluses low (median 124 kg N ha-1) via lower fertiliser and concentrate feed imports and higher stocking densities (median 2.1 livestock units ha-1). Using benchmarks as targets to encourage improvements in nutrient management could help farms achieve this potential and assist in achieving national objectives for sustainable agricultural production.