Alfalfa-grass mixtures reduce greenhouse gas emissions and net global warming potential while maintaining yield advantages over monocultures

Improving forage productivity with lower greenhouse gas (GHG) emissions from limited grassland has been a hotspot of interest in global agricultural production. In this study, we analyzed the effects of grasses (tall fescue, smooth bromegrass), legume (alfalfa), and alfalfa-grass (alfalfa + smooth bromegrass and alfalfa + tall fescue) mixtures on GHG emissions, net global warming potential (Net GWP), yield-based greenhouse gas intensity (GHGI), soil chemical properties and forage productivity in cultivated grassland in northwest China during 2020–2021. Our results demonstrated that alfalfa-grass mixtures significantly improved forage productivity. The highest total dry matter yield (DMY) during 2020 and 2021 was obtained from alfalfa-tall fescue (11,311 and 13,338 kg ha−1) and alfalfa-smooth bromegrass mixtures (10,781 and 12,467 kg ha−1). The annual cumulative GHG emissions from mixtures were lower than alfalfa monoculture. Alfalfa-grass mixtures significantly reduced GHGI compared with the grass or alfalfa monocultures. Furthermore, results indicated that grass, alfalfa and alfalfa-grass mixtures differentially affected soil chemical properties. Lower soil pH and C/N ratio were recorded in alfalfa monoculture. Alfalfa and mixtures increased soil organic carbon (SOC) and soil total nitrogen (STN) contents. Importantly, alfalfa-grass mixtures are necessary for improving forage productivity and mitigating the GHG emissions in this region. In conclusion, the alfalfa-tall fescue mixture lowered net GWP and GHGI in cultivated grassland while maintaining high forage productivity. These advanced agricultural practices could contribute to the development of climate-sustainable grassland production in China. The potential mechanisms that regulate the GHG (N2O, CH4, and CO2) production and consumption. Percentage of increase (+) and decrease (−) in GHG production and consumption, GWP, DMY, GHGI, and soil chemical properties in alfalfa-grass mixtures over grass monocultures. [Display omitted] •Yield of perennial grasses with alfalfa mixture were greater than monocultures.•Alfalfa and tall fescue mixture obtained greater yield than alfalfa and smooth bromegrass mixture.•The soil organic carbon and total nitrogen contents were improved by the alfalfa and mixtures.•Alfalfa monoculture emitted more greenhouse gas emissions compared with the mixtures.•Alfalfa and tall fescue mixture resulted in lower global warming potential and greenhouse gas intensity.