NITROGENOUS FERTILIZERS - GLOBAL DISTRIBUTION OF CONSUMPTION AND ASSOCIATED EMISSIONS OF NITROUS-OXIDE AND AMMONIA

The global distribution of nitrogen input via application of chemical nitrogenous fertilizers to agricultural ecosystems is presented. The s uite of 1 degrees (latitude/longitude) resolution data bases includes primary data on fertilizer consumption, as well as supporting data set s defining the distribution and intensity of agriculture associated wi th fertilizer use. The data were developed from a variety of sources a nd reflect conditions for the mid-1980s. East Asia, where fertilizer u se is increasing at similar to 10%/year, accounted for similar to 37% of the total, while North America and western Europe, where fertilizer use is leveling off, accounted for 17% and 14% of global use, respect ively. Former centrally planned economies of Europe consumed one fifth of the 1984 total, but rapid increases in the 1980s are slowing, and consumption trends are variable. The most widely used chemical nitroge nous fertilizer is urea which accounted for 40% of the world's total i n the mid-1980s. While almost every country consumes urea, similar to 75% of the large East Asian fertilizer use is supplied by this one fer tilizer. Ammonium nitrate, used primarily in the former centrally plan ned economies of Europe, in West Asia, and in Africa, accounted for ab out one quarter of global consumption. These data were used to estimat e distributions of the annual emission of nitrous oxide (N2O) and of a mmonia (NH3) associated with the use of fertilizers. Applying publishe d ranges of emission coefficients for fertilizer types in the data bas e yields a median emission of 0.1 Tg N2O-N, with lower and upper value s of 0.03 and 2.0 Tg N2O-N in 1984. This equals <1% to similar to 3% o f the total nitrogen applied via commercial fertilizers and represents <1% to 15% of the annual emission of N2O from terrestrial sources. As suming that the similar to 4% annual increase in consumption of nitrog enous fertilizers during the 1980s corresponds to a similar to 4% rise in the release of N2O-N, yearly increases in emissions from fertilize r use are <0.01 to 0.08 Tg N2O-N equal to <1% to 3% of the current gro wth of atmospheric nitrous oxide. However, since no measurements of fe rtilizer-derived nitrous oxide emissions are available for agricultura l environments in the tropics/subtropics, where similar to 40% of fert ilizer N is consumed and where consumption is increasing rapidly, rela tive contributions of climatic regions to current and future emissions remain uncertain. Ammonia emission coefficients for simple groups of fertilizer types were applied to derive the global distribution of amm onia volatilization associated with nitrogenous fertilizer consumption . The 1984 total of similar to 5-7 Tg NH3-N, about 10-15% of the annua l ammonia source, is concentrated overwhelmingly in subtropical Asia o wing to the dominant use of urea with high rates of volatilization. Ho wever, the paucity of measurements in representative ecological and ma nagement environments suggests that the magnitude and distribution of current and future ammonia emission from fertilizers is still poorly k nown.