|TURNER, P - University Of Minnesota|
|GRIFFIS, TIMOTHY - University Of Minnesota|
|Venterea, Rodney - Rod|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2016
Publication Date: 9/8/2016
Citation: Turner, P.A., Baker, J.M., Griffis, T.J., Venterea, R.T. 2016. The impact of kura clover living mulch on nitrous oxide emissions in a corn/soybean system. Journal of Environmental Quality. 45:1782-1787. doi:10.2134/jeq2016.01.0036.
Interpretive Summary: Nitrous oxide (N2O) is a major greenhouse gas, and also contributes to depletion of stratospheric ozone. The largest source of N2O is agriculture, so it is important to develop better understanding of the impact of various management practices on N2O emissions.Since emission rates are strongly correlated with the amount of inorganic N fertilizer that is applied, there have been suggestions that practices that reduce fertilizer needs might reduce emissions. One of those practices is the inclusion of legumes in crop rotations, since they provide biologically fixed N, reducing the need for N fertilizer. We examined the impact of growing corn in a perennial legume (kura clover) living mulch by continuosly measuring N2O emissions over two growing seasons in two adjacent systems: a conventional corn/soybean rotation and a sytem in which corn and soybeans were grown in a kura clover living mulch.In each system there were 4 automated chambers that measured emission rates once per hour. Emissions from the living mulch system were lower during the spring, but were higherin late summer and fall, probably due to senescence of the clover. Overall annual total emissions were actually higher from the clover living mulch system, casting doubt on the efficacy of using a legume living mulch to reduce N2O emissions.
Technical Abstract: Nitrous oxide (N2O) is a potent greenhouse gas and the dominant ozone depleting substance. Produced primarily in agricultural soils, efforts to reduce N2O emissions are underway, but mitigation results thus far have been inconsistent. The leguminous perennial kura clover (Trifolium ambiguum M. Bieb.) successfully grows side-by-side with cash crops in rotational corn (Zea mays L.) – soybean (Glycine max L.) systems. With biological nitrogen fixation, kura clover provides land managers an opportunity to reduce external fertilizer inputs that may reduce problematic N2O losses. To investigate the effect of a living mulch on N2O emission, automated soil chambers coupled to a N2O analyzer were used to measure hourly fluxes from March through November in a 2-yr corn-soybean rotation. Growing season emissions from the kura treatments were significantly greater than emissions from the conventional (no kura clover) treatment. A seasonal tradeoff was observed in the kura treatment wherein spring season emissions were reduced but were surpassed by high losses following periods of soil disturbance and post-harvest. These results represent the first-reported measurements of N2O emissions from a kura-based living mulch. The findings cast doubt on the efficacy of kura clover for mitigating N2O in corn-soybean systems. However, if kura clover reduces nitrate leaching losses, as has been reported elsewhere, it may result in lower indirect (offsite) N2O emissions.