, Volume 37, Issue 3, pp 191-200

Nitrous oxide emissions from agricultural soils

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Abstract

This paper addresses three topics related to N2O emissions from agricultural soils. First, an assessment of the current knowledge of N2O emissions from agricultural soils and the role of agricultural systems in the global N2O are discussed. Secondly, a critique on the methodology presented in the OECD/OCDE (1991) program on national inventories of N2O is presented. Finally, technical options for controlling N2O emissions from agricultural fields are discussed.

The amount of N2O derived from nitrogen applied to agricultural soils from atmospheric deposition, mineral N fertilizer, animal wastes or biologically fixed N, is not accurately known. It is estimated that the world-wide N2O emitteddirectly from agricultural fields as a result of the deposition of all the above nitrogen sources is 2–3 Tg N annually. This amounts to 20–30% of the total N2O emitted annually from the earth's surface. An unknown, but probably significant, amount of N2O is generated indirectly in on and off farm activities associated with food production and consumption.

Management options to limitdirect N2O emissions from N-fertilized soils should emphasize improving N-use efficiency. Such management options include managing irrigation frequency, timing and quantity; applying N only to meet crop demand through multiple applications during the growing season or by using controlled release fertilizers; applying sufficient N only to meet crop needs; or using nitrification inhibitors. Most of these options have not been field tested. Agricultural management practices may not appreciably affect indirect N2O emissions.