Journal Article

Nitrous oxide emissions from agricultural fields: assessment, measurement and mitigation

Freney, J.R, Minami, K, Mosier, A.R. (USDA-ARS, Fort Collins, CO (USA)), Duxbury, J.M, Heinemeyer, O

1996

Overview

In this paper we discuss three topics concerning N₂O emissions from agricultural systems. First, we present an appraisal of N₂O emissions from agricultural soils (Assessment). Secondly, we discuss some recent efforts to improve N₂O flux estimates in agricultural fields (Measurement), and finally, we relate recent studies which use nitrification inhibitors to decrease N₂O emissions from N-fertilized fields (Mitigation). To assess the global emission of N₂O from agricultural soils, the total flux should represent N₂O from all possible sources; native soil N, N from recent atmospheric deposition, past years fertilization, N from crop residues, N₂O from subsurface aquifers below the study area, and current N fertilization. Of these N sources only synthetic fertilizer and animal manures and the area of fields cropped with legumes have sufficient global data to estimate their input for N₂O production. The assessment of direct and indirect N₂O emissions we present was made by multiplying the amount of fertilizer N applied to agricultural lands by 2% and the area of land cropped to legumes by 4 kg N₂O-N ha⁻¹. No regard to method of N application, type of N, crop, climate or soil was given in these calculations, because the data are not available to include these variables in large scale assessments. Improved assessments should include these variables and should be used to drive process models for field, area, region and global scales. Several N₂O flux measurement techniques have been used in recent field studies which utilize small and ultralarge chambers and micrometeorological along with new analytical techniques to measure N₂O fluxes. These studies reveal that it is not the measurement technique that is providing much of the uncertainty in N₂O flux values found in the literature but rather the diverse combinations of physical and biological factors which control gas fluxes. A careful comparison of published literature narrows the range of observed fluxes as noted in the section on assessment. An array of careful field studies which compare a series of crops, fertilizer sources, and management techniques in controlled parallel experiments throughout the calendar year are needed to improve flux estimates and decrease uncertainty in prediction capability. There are a variety of management techniques which should conserve N and decrease the amount of N application needed to grow crops and to limit N₂O emissions. Using nitrification inhibitors is an option for decreasing fertilizer N use and additionally directly mitigating N₂O emissions. Case studies are presented which demonstrate the potential for using nitrification inhibitors to limit N₂O emissions from agricultural soils. Inhibitors may be selected for climatic conditions and type of cropping system as well as the type of nitrogen (solid mineral N, mineral N in solution, or organic waste materials) and applied with the fertilizers.

• Publisher: Kluwer Academic Publishers,Springer
• Subject: AGRICULTURAL SOILS / Agrology / Agronomy. Soil science and plant productions / Biological and medical sciences / Chemical, physicochemical, biochemical and biological properties / Clay soils / Fertilizers / Fundamental and applied biological sciences. Psychology / Grassland soils / INHIBIDORES DE LA NITRIFICACION / INHIBITEUR DE NITRIFICATION / NITRIFICACION / NITRIFICATION / NITRIFICATION INHIBITORS / Nitrogen / NITROUS OXIDE / Organic matter / OXIDO NITROSO / OXYDE NITREUX / Physics, chemistry, biochemistry and biology of agricultural and forest soils / Pollutant emissions / Soil air / Soil science / SOL AGRICOLE / SUELOS AGRICOLAS