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

Abstract

A.R. M o s i e r I , J.M. D u x b u r y 2, J.R. F r e n e y 3, O. H e i n e m e y e r 4 and K. M i n a m i 5 I USDA/ARS, AbstractIn this paper we discuss three topics concerning N20 emissions from agricultural systems. First, we present an appraisal of N20 emissions from agricultural soils (Assessment). Secondly, we discuss some recent efforts to improve N20 flux estimates in agricultural fields (Measurement), and finally, we relate recent studies which use nitrification inhibitors to decrease N20 emissions from N-fertilized fields (Mitigation).To assess the global emission of N20 from agricultural soils, the total flux should represent NzO from all possible sources; native soil N, N from recent atmospheric deposition, past years fertilization, N from crop residues, N20 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 N20 production. The assessment of direct and indirect N20 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 N20-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 N20 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 N20 fluxes. These studies reveal that it is not the measurement technique that is providing much of the uncertainty in N20 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 N20 emissions. Using nitrification inhibitors is an option for decreasing fertilizer N use and additionally directly mitigating N20 emissions. Case studies are presented which demonstrate the potential for using nitrification inhibitors to limit N20 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.

N2O and NO emission from agricultural fields and soils under natural vegetation: summarizing available measurement data and modeling of global annual emissions

“…The controlling factors of N 2 O and NO emissions have been reviewed elsewhere (for example, Firestone and Davidson 1989;Robertson 1989;Bouwman et al 1993;Mosier et al 1996;Bremner 1997;Freney 1997;Bouwman et al 2002a).…”

Nitric and nitrous oxide emissions following fertilizer application to agricultural soil: Biotic and abiotic mechanisms and kinetics

“…The oxidation of N20 to NO in the stratosphere promotes 03 destruction [Crutzen, 1981]. There is a recognized need for improved understanding of the factors responsible for high variabilities observed in measurements of NO and N20 emissions from soils [Matson, 1997;Mosier et al, 1996] in order to reduce uncertainties in global budgeting efforts [Davidson and Kingerlee, 1997] and to aid in the development of strategies for mitigating N losses from intensively fertilized agricultural systems [Matson et al, 1998]. …”

Potential for biological nitrification inhibition to reduce nitrification and N2O emissions in pasture crop–livestock systems

“…In contrast, NO 3 2 , with negative charge, does not readily bond to the soil, and is more labile to be leached out of the root zone. In addition, several heterotrophic soil bacteria denitrify NO 3 2 under anaerobic or partially anaerobic conditions (which can often coincide with temporary water-logging of a soil after a heavy rainfall or irrigation in fields that have improper drainage; Bremner and Blackmer, 1978;Mosier et al, 1996). The loss of nitrogen (N) during and following nitrification reduces the effectiveness of N fertilization, causing environmental degradation, loss of biodiversity, loss of ecosystem services, emergence of pathogens and threatening the long-term sustainability of agricultural production systems (Clark, 1962;Jarvis, 1996;Vitousek et al, 1997a and1997b;Dalgaard et al, 2012).…”