Aarhus University Seal / Aarhus Universitets segl

Moderate reductions in agricultural nutrient surpluses

The surpluses of nitrogen, phosphorus and potassium in agriculture continue their downward trend.

The nutrient surpluses in agriculture have seen steady decreases over the last 25 years. In the production 2010/2011 year, the surplus is, however, larger than in the previous year, but as an average of the last two-three years, it results in a moderate fall in the nitrogen and potassium surpluses, whereas the phosphorus surplus remains static in relation to 2009/2010.

 

The quantities of nitrogen, phosphorus and potassium that can potentially be discharged to the environment are steadily falling. This is the result of a report from DCA – Danish Centre for Food and Agriculture at Aarhus University.

 

- For nutrients where a loss has an adverse impact on the environment, the surplus is a good indicator of the development in the potential impact of agriculture on the environment when seen over a number of years, says the report.

 

Each year Aarhus University provides an update of the nutrient balances for the last 20 years at national level for the agricultural use of nitrogen (N), phosphorus (P) and potassium (K), including a calculation of the surplus and the nutrient use efficiency of the three nutrients. The results from 2010/2011 are now available in the report published by DCA.

 

Input minus output equals surplus

The nutrient surplus corresponds to what remains in the agricultural system when the nutrient import in feedstuffs and mineral fertiliser has been subtracted from nutrient export via sales of plant and animal products.

 

The surplus corresponds to what can potentially be lost via ammonia volatilisation from buildings and stores and via application, denitrification, leaching, surface runoff, and incorporation into the soil organic matter pool.

 

Seen over a number of years, the principal explanation for a reduction in nutrient surpluses in agriculture is a falling demand for mineral fertiliser for crops.

 

The calculation for 2009/10 shows a considerable reduction in the surplus of both N, P and K compared with previous years – primarily because of the high yields in both 2008 and 2009, which meant a large export in cash crops. In 2010 the yields were more moderate, and the surplus in 2010/11 is therefore somewhat higher than in 2009/10, but as an average of the last three years there is still a moderate fall in the surpluses.

 

The report (in Danish) ”Næringsstofbalancer og næringsstofoverskud i landbruget 1990/91-2010/11, DCA report no. 8, June 2012” can be downloaded from here.

 

Further information: Senior scientist Finn Pilgaard Vinther, Department of Agroecology, e-mail: finn.vinther@agrsci.dk, telephone: +45 8715 7675