MODELING NITROUS OXIDE

EMISSIONS IN AGRICULTURE

 

 

Developing and utilizing accurate computer Decision Support Systems (DSS) for nitrous oxide (N2O) emissions from soils could help predict how various land use management practices would affect emissions of this greenhouse gas. William Salas, president of Applied Geosolutions, LLC is developing a geospatial DSS for N2O emissions, utilizing an assortment of digital data, research data, and a biogeochemical model. The DSS is being used estimate and map nitrous oxide emissions at various site levels, and the potential effect of land management practices on these emissions. Salas is also working on methods for scaling up the results to extrapolate from site scale to watershed scale and beyond.

 

The biogeochemical model being used by Salas is the process-oriented DNDC (DeNitrification-DeComposition), developed by Changseng Li, of the University of New Hampshire’s Institute for the Study of Earth, Oceans, and Space. The core of DNDC is a soil biogeochemical model, which can be linked to various other models or GIS and climate databases for purposes of mapping or estimating the fate of carbon and nitrogen in a terrestrial system.

 

The core DNDC model is based on biogeochemical concepts for predicting soil carbon and nitrogen fluxes. The model links the impact of specified ecological drivers (climate, topography, soil, vegetation, and anthropogenic activity) on carbon, nitrogen, and water cycles. All three elemental cycles (C, N, and water) are linked through a biogeochemical field that includes radiation, temperature, moisture, pH, Eh, and substrate gradients.   

 

Salas is using the DNDC Biogeochemical Process model in combination with GIS-based spatial information to produce the NUGGET-DNDC data mapping tool -- a web-based, GIS-based Decision Support System for predicting the fate of C and N in a given site.

 

Salas first incorporates data on climate, soils, land use cropland management practices, and hydrology. He uses a variety of climate data in developing the NUGGET-DNDC mapping tool, including DAYMET, NEXRAD, and NCDC station data for the U.S. For soils data, Salas uses STATSGO and SSURGO. The land use and crop management data come from a combination of aerial photos, satellite data (Landsat, MODIS, and SAR), and USDA Census reports.

 

Once this basic data have been compiled for a given site, the next step is to take into account the effect of different agricultural management practices (using field research data). This information is then processed through the DNDC model, which simulates the carbon and nitrogen cycles and incorporates the biological and physical factors that affect those cycles. The final analysis is subject to whatever sensitivity analysis is desired, and a product is generated.

 

The final product is a map of the site (such as a watershed) showing a predicted range of possible nitrous oxide emissions at each point in the site as a result of changes in management practices. The NUGGET-DNDC Decision Support System is being used to assess the impact of agricultural management practices on the release of carbon and nitrogen to air and water. The goal is to be able to develop site-specific best management practices for increasing soil carbon and reducing nitrogen emissions and losses in a given site.

 

NUGGET-DNDC was developed with support from the USDA Small Business Innovative Research program.

 

Background on the NUGGET-DNDC mapping tool can be found at http://www.appliedgeosolutions.com. For information on the DNDC models, check out the “Resources” section of that web site. Li’s DNDC model web page is at: http://dndc.sr.unh.edu

 

For more information on the NUGGET-DNDC mapping tool, contact William Salas at wsalas@agsemail.com.

 

-- Steve Watson, Editor

swatson@ksu.edu