Global estimates of gaseous emissions of NH3 , NO and N2O from agricultural land

Abstract

This report describes global estimates of N2O and NO emissions and NH3 volatilization losses from fertilizer and manure application to fields used for crop production. Their quantification is important for assessing N fertilizer efficiency and their impact on atmospheric pollution and ecosystem acidification and eutrophication. The report reviews the literature and examines the regulating factors (e.g. N application rate) and measurement techniques for N2O and NOx emissions and NH3 volatilization. Using models, it generates global annual estimates: 3.5 million t of N2O-N emission and 2.0 million t of NO-N emission from crop and grassland. Estimated by fertilizer type, the emissions induced by fertilizers amount to 0.9 and 0.5 Mt respectively or approximately 0.8 and 0.5 percent respectively of current nitrogen fertilizer input. An NH3 loss of 14 percent of mineral fertilizer N use (higher in developing countries), while that from animal manure is 22 percent (60 percent from developed countries). The results for NH3 volatilization agree with other inventories, though NH3 volatilization from some fertilizers appears higher than previously thought. The outcome of the model shows that the potential impact of fertilizer use regulations would be modest from a global emission perspective. The quantities involved, however, constitute a valuable plant nutrient source. Farmers' ability to curtail such losses will primarily relate to economic incentives, in particular in South and South East Asia