Impact of kura clover living mulch on nitrous oxide emissions in a corn-soybean system

Nitrous oxide (N₂O), produced primarily in agricultural soils, is a potent greenhouse gas and is the dominant ozone-depleting substance. Efforts to reduce N₂O emissions are underway, but mitigation results have been inconsistent. The leguminous perennial kura clover (Trifolium ambiguum M. Bieb.) (KC) can grow side-by-side with cash crops in rotational corn (Zea mays L.)- soybean (Glycine max L.) systems. With biological nitrogen fixation, KC provides land managers an opportunity to reduce external fertilizer inputs, which may diminish problematic N₂O emissions. To investigate the effect of a KC living mulch on N₂O emissions, automated soil chambers coupled to a N₂O analyzer were used to measure hourly fluxes from April through October in a 2-yr corn-soybean (CS) rotation. Emissions from the KC treatment were significantly greater than those from the conventional CS treatment despite the fact that the KC treatment received substantially less inorganic nitrogen fertilizer. A seasonal tradeoffwas observed with the KC treatment wherein emissions before strip-tillage were reduced but were surpassed by high losses after strip-tillage and postanthesis. These results represent the first reported measurements of N₂O emissions from a KCbased living mulch. The findings cast doubt on the efficacy of KC for mitigating N₂O loss in CS systems. However, if KC reduces nitrate leaching losses, as has been reported elsewhere, it may result in lower indirect (offsite) N₂O emissions.