Location: Soil, Water & Air Resources ResearchTitle: Rye cover crop effects on direct and indirect nitrous oxide emissions Author
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2016
Publication Date: 12/15/2016
Citation: Parkin, T.B., Kaspar, T.C., Jaynes, D.B., Moorman, T.B. 2016. Rye cover crop effects on direct and indirect nitrous oxide emissions. Soil Science Society of America Journal. 80(6):1551-1559. doi: 10.2136/sssaj2016.04.0120.
Interpretive Summary: Corn and soybean agriculture are a significant source of the greenhouse gas, nitrous oxide (N2O). Nitrous oxide is formed in soil when excess fertilizer or soil nitrogen is used by soil microorganisms. Cover crops can be used together with corn and soybean production to take up excess nitrogen in soil. This study was conducted to examine whether a rye cover crop, by taking up excess nitrogen, would reduce emissions of N2O. Over a 10 year period we observed that direct emissions of N2O from soil tended to be lower from the rye cover crop treatment, however, this observation was not statistically significant. The cover crop was found to significantly decrease nitrate nitrogen leaching losses, thus, any off-site production of N2O should also be reduced. This information should be of use to policy makers and other scientists.
Technical Abstract: Winter cover crops can have a pronounced effect on N cycling in agricultural ecosystems. By reducing available soil mineral N during active growth and by providing a substrate for denitrifying bacteria after they are killed, cover crops can potentially influence soil N2O emissions. However, there have been conflicting reports regarding cover crop effects on increasing or decreasing N2O emissions. In this study direct soil emissions of N2O were measured over a 10 y period in a corn (Zea mays L.)/soybean (Glycine max (L.) Merr.) rotation with and without a winter rye (Secale cereale L.) cover crop. Additionally, NO3 leaching losses over the period were measured and used to estimate indirect N2O emissions. Direct N2O emissions measurements were measured using vented static chambers from March 2004 through December 2012. Cumulative N2O emissions were calculated each year by numerical integration. A tile drainage line in the center of each plot allowed for determination of NO3–N losses in tile drainage water. Indirect N2O emissions were estimated by applying the IPCC EF5 emission factor of 0.0075 kg N2O-N kg NO3-N leached-1. There was no significant effect of the rye cover crop on direct N2O emissions, however, emissions were different between corn and soybeans (P=0.013). Under corn N2O emissions ranged from 2.3 to 12.5 kg N2O-N ha-1 y-1, and under soybeans emissions ranged from 1.02 to 6.94 kg N2O-N ha-1 y-1. The rye cover crop did effect indirect emissions (P= 0.046), which were 1.25 kg N2O-N ha-1 y-1 in the rye treatment and 2.69 kg N2O-N ha-1 y-1 in the no-rye treatment. While total N2O emissions (direct + indirect) over 10 years tended to be lower in the rye cover crop treatment (56.2 kg N2O-N ha-1 y-1) compared to the no-rye treatment (64.4 kg N2O-N ha-1 y-1), this difference was not significant (P = 0.155). Large year-to-year variations in precipitation appeared to be a major determinant of annual N2O losses.