Ways to reduce nitrogen pollution from Swedish pork production

The aim of this paper is to examine measures in Swedish pork production to improve N-use efficiency and to reduce N-pollution of water and air. The entire chain of feed production, animal feed conversion and the use of animal manure is included, as well as the spatial allocation of pork production. A calculation model is developed using experimental data. It is simple and possible to use in practical environmental control. Using catch crops and halving N-input in feed grain production reduces N-leaching up to 25% per hectare. These measures have considerably less effect on leaching per kilo of produced animal growth and NH3-losses than on leaching per hectare. Reduced protein level in feed and Specific Pathogen Free pig production reduce both leaching and volatilisation, especially per kilo of animal growth. These animal-centred measures can also be profitable for many producers. Spreading all manure in spring and rapid incorporation is an effective way to reduce N-losses. However, as with catch crops and reduced fertilization, it is associated with considerable costs for the producers. A combination of best manure handling, catch crops and low protein feeding can reduce N-leaching and volatilisation up to 50%. Leaching from pig production on clay soil in Central Sweden is only one third of that on sandy soil in southwest Sweden. Spatial allocation of pork production also influences the environmental effects of N losses. These effects can be more negative in coastal zones with high N-deposition and low N-retention before the water reaches the sea, than in interior regions of Sweden with low original deposition. The results indicate that improved animal protein conversion, and especially suitable spatial allocation of pig production, are more cost-effective than additional measures in feed production and manure handling.