Identification of overlooked controls on soil nitrous oxide production.
Nitrous oxide (N2O) is a potent greenhouse gas and ozone depleting chemical that is emitted to the atmosphere following application of nitrogen fertilizers or deposition of animal wastes to soil. Improved understanding of the processes regulating N2O production in soil is critical to better estimation and mitigation of N2O emissions. This study was the first to find that differences in the capacity of soils to adsorb N fertilizer in the form of ammonium onto their surfaces is a key factor controlling differences in rates of N2O production. We also found that decreased surface ammonium sorption inhibited a certain class of soil bacteria which can act to reduce N2O production. These results will be useful to scientists and land managers interested in developing improved N2O emissions models, and in developing management practices to reduce N2O emissions.
Publication: Venterea R.T., T.J. Clough, J.A. Coulter and F. Breuillin-Sessoms. 2015. Ammonium sorption and ammonia inhibition of nitrite-oxidizing bacteria explain contrasting soil N2O production. Scientific Reports, 5, Article number: 12153, doi:10.1038/srep12153.
Delayed timing of fertilizer application may increase nitrous oxide emissions.
Modification of fertilizer management practices to reduce emissions of N2O has been identified as a key strategy for reducing the greenhouse gas footprint of agricultural cropping systems. Altering the timing of N fertilizer application is frequently mentioned as a potentially effective practice for reducing all forms of N loss from fertilized soil. However, in this two year field study, we found that application of N fertilizer later in the growing season did not necessarily reduce, but actually increased, N2O emissions. This resulted from variation in rainfall and soil moisture which are not easily predicted or managed in rainfed systems. These results provide important information for developing effective practices to reduce soil N2O emissions.
Publication: Venterea, R.T. and J.A. Coulter. 2015. Split application of urea does not decrease and may increase N2O emissions in rainfed corn. Agronomy Journal, 107. doi:10.2134/agronj14.041.
Soil nitrite dynamics explain fertilizer management effects on nitrous oxide emissions.
It is typically assumed that the dependence of nitrous oxide emissions on soil nitrogen availability is best quantified in terms of ammonium and/or nitrate concentrations. In contrast, nitrite (NO2-) is seldom measured separately from nitrate despite its role as a central substrate in nitrous oxide production. We examined the effects of three fertilizer sources and two placement methods on nitrous oxide in corn over two growing seasons. Cumulative nitrous oxide emissions were well-correlated with nitrite intensity but not with nitrate or ammonium intensity. By itself, nitrite intensity explained more than 44% of the overall variance in cumulative nitrous oxide emissions. These results show that practices which reduce nitrite accumulation have the potential to also reduce nitrous oxide emissions, and that separate consideration of nitrite and nitrate dynamics can provide more insight than their combined dynamics as typically quantified.
Publication: Maharjan, B. and R.T. Venterea. 2013. Nitrite intensity explains N management effects on N2O emissions in maize. Soil Biology and Biochemistry. 66:229-238.
International guidelines for improved nitrous oxide emissions measurements.
Soil nitrous oxide emissions are in many cases the largest component of the greenhouse gas impact of agricultural systems. However, measurements of nitrous oxide fluxes are highly sensitive to the methods deployed and there is currently wide variation in methodologies. Working as part of an international team of experts from 10 countries, we developed a set of peer-reviewed methods guidelines that are being distributed internationally via the website of the Global Research Alliance. These guidelines will be useful to scientists and technicians from around the world engaged in research related to agricultural nitrous oxide emissions and will result in more accurate and precise measurement of nitrous oxide emissions from croplands and grazing lands. Publications: Venterea, R.T., Parkin, T.B., Cardebas, L., Petersen, S.O., Petersen, A.R. 2012. Data analysis considerations (Chapter 6). In: Deklein, C., Harvey, M., editors. Nitrous Oxide Chamber Methodology Guidelines. Global Research Alliance on Agricultural Greenhouse Gas Emissions.