Consequences of new scientific findings for future abatement of ammonia emissions

Several studies have shown that the estimated decreases in emissions of ammonia in the Netherlands are overestimated. Results obtained from recent research on the so-called compensation point of ammonia in intensive farming areas, research in areas affected with swine fever, and research on emissions following application, all show that the decrease in emissions of ammonia expected to be achieved by injection of manure into the soil is not obtained when the amount of nitrogen greatly exceeds the crop need. The amount of nitrogen applied to Dutch soils has exceeded crop and grass needs for some years. When this condition continues for a long time it appears that ammonia available in the manure or soil will be emitted from the crop/soil system as the result of changes in the air-soil/vegetation equilibrium. If this hypothesis is true we have to reconsider the current strategies for management of ammonia emissions in intensive farming areas. The emphasis should be on limitations of the total amount of nitrogen applied to soils rather than on increasing the effectiveness of injection of manure. Furthermore, the N-cycle should be considered as a whole and nitrogen management approached should be adjusted so they are optimal for both nitrogen management and crop production efficiency. The technological measures that should be explored include chemical binding of nitrogen in manure or in soil, manure processing on farm level with the emphasis on fixation of ammonium or extraction of ammonia from the manure, combined with further processing into specific fertiliser products, and for de-nitrification to N-2.