|TURNER, PETER - University Of Minnesota|
|GRIFFIS, TIMOTHY - University Of Minnesota|
|MULLA, D - University Of Minnesota|
|Venterea, Rodney - Rod|
Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2016
Publication Date: 9/1/2016
Citation: Turner, P., Griffis, T.J., Mulla, D.J., Baker, J.M., Venterea, R.T. 2016. A geostatistical approach to identify and mitigate agricultural nitrous oxide emission hotspots. Science of the Total Environment. 572:442-449. doi:10.1016/j.scitotenv.2016.08.094.
Interpretive Summary: Nitrous oxide (N2O) is a greenhouse gas, nearly 300 times as potent per molecule as CO2. Agricultural production is the primary source of N2O, and there is thus much interest in measuring the amount of N2O emission from different management systems in order to determine mitigation strategies. The primary method of choice has been static chambers. These small chambers (typically 10-20 cm in diameter) are pushed into the soil at selected locations within a field. Emission measurements are made by taking syringe samples of the gas inside the chamber at regular intervals (e.g once every 10 minutes for an hour) in order to calculate the rate of change of N2O concentration within the chamber, from which the emission rate can be calculated. Unfortunately, N2O emissions have high spatial variability, and it is difficult to know where to place multiple chambers to get a repreentative result for a whole field. We used terrain attributes and geospatial statistics to identify "hotspots" and "coldspots" in a field, where emission rates would be higher and lower, respectively than other positions in the field. Emission rates from the hotspots were twice as high as those from other parts of the field, and though they represented only 21% of the field they accounted for 36% of the N2O emission from the field. This technique could be valuable in predicting where mitigation practices could be most effective in reducing N2O losses.
Technical Abstract: Anthropogenic emissions of nitrous oxide (N2O), a trace gas with severe environmental costs, are greatest from agricultural soils amended with nitrogen (N) fertilizer. However, accurate N2O emission estimates at fine spatial scales are made difficult by their high variability, which represents a critical challenge for the management of N2O emissions. Here, static chamber measurements (n = 60) and soil samples (n = 129) were collected for 42-d immediately following the application of N in a southern Minnesota cornfield (15.6-ha), typical of the systems prevalent throughout the U.S. Corn Belt. These data were integrated into a geostatistical model that resolved N2O emissions at high spatial resolution (1-m). Field-scale N2O emissions exhibited a high degree of spatial variability, and were partitioned into three classes of emission strength: hotspots, intermediate, and coldspots. Rates of emission from hotspots were 2-fold greater than non-hotspot locations. Consequently, 36% of the field-scale emissions could be attributed to hotspots, despite representing only 21% of the total field area. Our data and analyses indicate that targeted management of hotspots could efficiently reduce field-scale emissions by nearly 20%, a significant benefit considering the deleterious effects of atmospheric N2O.