Search for: All records

Abstract. Nitrogen (N) fertilizer inputs to agricultural soils area leading cause of nitrous oxide (N2O) emissions. Legume cover cropsare an alternative N source that can reduce agricultural N2O emissionscompared to fertilizer N. However, our understanding of episodic N2Oflux following cover crop incorporation by tillage is limited and hasfocused on single-species cover crops. Our study explores whether increasingcover crop functional diversity with a legume–grass mixture can reduce pulseemissions of N2O following tillage. In a field experiment, we plantedcrimson clover (Trifolium incarnatum L.), cereal rye (Secale cereal L.), a clover–rye mixture, and a no-covercontrol at two field sites with contrasting soil fertility properties inMichigan. We hypothesized that N2O flux following tillage of the covercrops would be lower in the mixture and rye compared to the clovertreatment because rye litter can decrease N mineralization rates. Wemeasured N2O for approximately 2 weeks following tillage to capturethe first peak in N2O emissions in each site. Across cover croptreatments, the higher-fertility site, CF, had greater cover crop biomass,2-fold-higher aboveground biomass N, and higher cumulative N2Oemissions than the lower-fertility site, KBS (413.4±67.5 vs. 230.8±42.5 g N2O-N ha−1; P=0.004). Therewas a significant treatment effect on daily emissions at both sites. AtCF, N2O fluxes were higher following clover than the control 6 d aftertillage. At KBS, fluxes from the mixture were higher than rye 8 and 11 dafter tillage. When controlling for soil fertility differences betweensites, clover and mixture led to approximately 2-fold-higher N2Oemissions compared to rye and fallow treatments. We found partial supportfor our hypothesis that N2O would be lower following incorporation ofthe mixture than clover. However, treatment patterns differed by site,suggesting that interactions between cover crop functional types andbackground soil fertility influence N2O emissions during cover cropdecomposition.