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Strategies to mitigate nitrous oxide emissions from herbivore production systems

Schils, R. L. M., Eriksen, J., Ledgard, S. F., Vellinga, Th. V., Kuikman, P. J., Luo, J., Petersen, S. O., Velthof, G. L.
Animal 2013 v.7 no.s1 pp. 29-40
adverse effects, ammonia, animal housing, breeding, carbon, carbon dioxide, diet, farmers, fertilizers, forage production, grazing, grazing lands, greenhouse gas emissions, greenhouse gases, herbivores, issues and policy, livestock, methane, nitrification inhibitors, nitrogen, nitrous oxide, nutrient use efficiency, pastures, proanthocyanidins, production technology, soil
Herbivores are a significant source of nitrous oxide (N₂O) emissions. They account for a large share of manure-related N₂O emissions, as well as soil-related N₂O emissions through the use of grazing land, and land for feed and forage production. It is widely acknowledged that mitigation measures are necessary to avoid an increase in N₂O emissions while meeting the growing global food demand. The production and emissions of N₂O are closely linked to the efficiency of nitrogen (N) transfer between the major components of a livestock system, that is, animal, manure, soil and crop. Therefore, mitigation options in this paper have been structured along these N pathways. Mitigation technologies involving diet-based intervention include lowering the CP content or increasing the condensed tannin content of the diet. Animal-related mitigation options also include breeding for improved N conversion and high animal productivity. The main soil-based mitigation measures include efficient use of fertilizer and manure, including the use of nitrification inhibitors. In pasture-based systems with animal housing facilities, reducing grazing time is an effective option to reduce N₂O losses. Crop-based options comprise breeding efforts for increased N-use efficiency and the use of pastures with N₂-fixing clover. It is important to recognize that all N₂O mitigation options affect the N and carbon cycles of livestock systems. Therefore, care should be taken that reductions in N₂O emissions are not offset by unwanted increases in ammonia, methane or carbon dioxide emissions. Despite the abundant availability of mitigation options, implementation in practice is still lagging. Actual implementation will only follow after increased awareness among farmers and greenhouse gases targeted policies. So far, reductions in N₂O emissions that have been achieved are mostly a positive side effect of other N-targeted policies.