Denitrification in cropping systems at sub-zero soil temperatures. A reviewRebecca L. Phillips
USDA-ARS, Box 459, Mandan, ND 58554, USA
(Accepted 26 September 2007; published online 18 December 2007)
Abstract - Nitrogen (N) in agricultural fertilizers is denitrified by soil bacteria when oxygen is limited, which effectively removes plant-available N from the soil to the atmosphere. Reported denitrification rates range from 0 to 239 kg N ha-1 yr-1, and, depending upon environmental conditions and management, may reduce the amount of N available for crop growth by 27%. Denitrification in soils also results in emissions of nitrous oxide (N2O), which is a recognized pollutant that contributes to stratospheric ozone destruction and radiative forcing in the troposphere. Practitioners of sustainable agronomy aim to improve plant N-use efficiency and reduce emissions of the greenhouse gases by synchronizing N application and plant nutritional requirements. However, it is difficult to predict denitrification rates during and after the growing season based on current knowledge. High rates are consistently reported in irrigated cropping systems following heavy applications of fertilizer-N, but few studies report denitrification during the dormant season. Denitrification in winter may represent a significant sink for fertilizer-N in cropping systems, but further research at sub-zero soil temperatures is needed. Here, the three factors required for microbial denitrification: limited O2 availability, electron donors and electron acceptors, are reviewed based on soil research performed both above and below 0 °C. Gaps in the knowledge of denitrification rates in cropping systems, particularly when soils are frozen, are identified. Sustainable management of N in cropping systems such as greater N-use efficiency and lower greenhouse gas emissions could be advanced by greater understanding of denitrification in winter.
Key words: nitrous oxide / sub-zero temperatures / nitrogen / fertilizer
Corresponding author: Rebecca.email@example.com
© INRA, EDP Sciences 2007