Evaluation of historical global gaseous nitrogen emissions from croplands considering NH4+ and NO3- forming fertilizer species in global fertilizer dataset

Kazuya NISHINA, Akihiko ITO, Seiji HAYASHI

1 National Institute for Environmental Studies 16-2, Onogawa, Tsukuba, 305-8506, JAPAN, https://www.nies.go.jp/chiiki/en/index_en.html, nishina.kazuya@nies.go.jp


We developed a new historical global N fertilizer map (half degree resolution) during 1961-2010 based on FAOSTAT and various global dataset. This new map incorporated the fraction of NH4+ (and NO3) into N fertilizer inputs by utilizing fertilizer species information in FAOSTAT. In the data processing, we applied a statistical data imputation method for the missing data in FAOSTAT. The multiple imputation method enabled to fill gaps of the time-series data by the plausible values. In this study, we evaluated NH3, NO, and N2O emissions from agricultural soils with biogeochemical model “VISIT” using the developed map. During 1961-2010, synthetic fertilizer consumption increased from 15 Tg-N to 110 Tg-N at global. In this period, the global average fraction of NH4+ was about 80% to synthetic N fertilizer consumption. The most countries showed NH4+ based fertilizer are dominant, however, the ratio NH4+:NO3 in N fertilizer inputs shows clear differences among countries and periods. Considering the ratio NH4+:NO3 in N fertilizer inputs, the simulated NH3 volatilization were generally reduced, compared to N fertilizer input dealt as only NH4+input assumption. On the other hand, NO and N2O emissions shows both positive and negative impacts using the NH4+:NO3 fertilizer map. Our new map can be utilized and bring new insights in the global model studies for the assessment of historical terrestrial N cycling changes.