CAN ORGANIC FARMING HELP TO REDUCE N-LOSSES - EXPERIENCES FROM DENMARK

This study is in two parts. In the first part, nitrogen (N) losses per unit of milk and meat in Danish conventional and organic pig and dair y farming were compared on the basis of farm data. In the second part, organic and conventional dairy farming were compared in detail, using modelling. N-surpluses at different livestock densities, fodder inten sities, and soil types were simulated. Finally, simulated N-surpluses were used in national scenarios for conversion to organic dairy farmin g in Denmark. In Part one, pig farming was found to have a higher N-ef ficiency than dairy farming. Organic pig production had a lower N-effi ciency and a higher N-surplus per kg meat than conventional pig produc tion. The possibilities to reduce N-loss by conversion to organic pig production therefore appear to be poor. Organic dairy farming had a hi gher N-efficiency and a lower N-surplus per kg milk than conventional dairy farming. Conversion from conventional to organic dairy farming m ay therefore reduce N-losses. In Part two, a positive correlation betw een livestock density and N-surplus ha(-1) was found for dairy farming . For all simulated livestock densities, fodder feeding intensities an d soil types, organic systems showed a lower N-surplus per unit of mil k produced than conventional systems. National scenarios for dairy far ming showed that the present Danish milk production could be achieved with a 24% lower total N-surplus if converted from intensive conventio nal farming to extensive organic farming. At the same time, N-surplus ha(-1) and N-surplus (t milk)(-1) would be lowered by 50% and 25% resp ectively. Changing from intensive to extensive conventional dairy farm ing with a livestock density equal to that in the organic scenario res ulted in a reduction in N-surplus ha-l of 15%. It was concluded that a reduction in total N-loss from agriculture is possible by converting from conventional to organic dairy fanning but at the cost of either l ower production on the present dairy farm area, or the current product ion on a substantially larger area.