Early research on denitrification along a managementintensity gradient

Parr, S. and G.P. Robertson

Presented at the All Scientist Meeting (2004-10-08 )

Denitrification is the microbial reduction of soil nitrate, a crucial and often limiting plant nutrient, to nitrogen oxide gases, of which N2O and NOx are important air pollutants (Robertson 2000, Houghton et al., 2001) By monitoring denitrification, this process is useful in examining the impact of humans on a major biogeochemical cycle. Known controls of denitrification, including nitrate, water content of soil, and carbon sources, are known to vary along a management gradient, it is feasible that denitrification will also vary along a management gradient. I will compare the denitrification rates among the different management regimes, starting with conventional tillage, successional field, and deciduous forest sites. This experiment was performed at the Long Term Ecological Research Site at Kellogg Biological Research Station in Hickory Corners, Michigan. Since denitrification causes the production of the greenhouse gas nitrous oxide, my objective is to find out if some management systems reduce or enhance nitrogen losses through denitrification. This has implications for greenhouse gas mitigation, global climate change, and increased primary production due to greater nitrogen availability in the soils. This research aims to contribute to the regional nitrogen budget, for which denitrification currently stands as large gap in understanding and nitrogen accounting. All treatments were found to be significantly different in their production of N2O-N per gram of soil per hour (P<0.0001). This could partially be explained by the differences in bulk density of the soil and resultant water holding capacities and/or nutrient compositions.Though numerous studies have shown that water content of the soil is a major predictor of denitrification (Groffman et al 1988, Tiedje 1987, Linn and Doran 1984), this study did not support that hypothesis. The range of soil moisture was from about 10-20 percent by weight, which may be part of the reason for the lack of significance (P=0.3828). Future research includes further analyzing the nutrient composition of the soil, and investigating correlations between denitrification and N content of the soils. This will further the development of a predictive model of denitrification.

Back to meeting | Show |
Sign In