Nitrogen inputs and outputs for New Zealand in 2001 at national and regional scales

The Nanjing Declaration on Nitrogen Management, signed in Nanjing in October 2004, calls for national governments to optimize N management by several strategies including assessment of N cycles. Here we develop a first N budget for New Zealand ( 267,000 km 2), at both national and regional scales. The national inputs are estimated to be 36.5 kg/ ha, mainly from biological N.xation, but also increasingly from fertilizer application and atmospheric deposition. The outputs are estimated at 40.5 kg/ ha. Biological N.xation from legumes in pasture was the most important input in most regions. Exceptions were Auckland, with a large urban population, and the West Coast of the South Island, with large tracts of rain forest. Outputs were distributed in the order leaching > ammonia volatilisation > erosion = produce = denitrification. These outputs are very different from global averages because of the large numbers of grazing animals on pasture. A large loss occurs between the subsoil and the oceans, and further research is needed to identify these pathways. Riverine export of N was generally well correlated with inputs.