Using Diverse Cover Crop Mixtures to Provide Ecosystem Services.

Increasing plant diversity in agroecosystems with cover crops has been a successful strategy to augment ecosystem services from agriculture, and increasing diversity within cover cropping systems may provide even greater benefits. Biomass production and ecosystem services from multi-species cover crop mixtures were measured in a two year field study of eighteen cover crop treatments preceding corn in central Pennsylvania. While increasing the number of species in a stand generally increased cover crop biomass (P<0.05, R²=0.15), mixing cover crop species that were complementary in phenology or nitrogen (N) acquisition strategy did not result in mixtures that produced more biomass than high-yielding monocultures. Increasing cover crop biomass was positively correlated with several ecosystem services, namely weed suppression, prevention of nitrate leaching, and biomass N content, but negatively impacted inorganic N availability and corn yield in the subsequent cropping season. The carbon to nitrogen ratio of cover crop biomass was another determinant of ecosystem services that was positively related to leaching prevention, but negatively related to inorganic N availability and corn yield. This study confirms the long-held assumption that increasing biomass production can enhance certain ecosystem services from cover crops; however, unless a mixture provides more biomass than a high yielding monoculture, planting a mixture will not be an efficient strategy to increase biomass-driven services. This study also demonstrates that species functional traits (as opposed to biomass alone) will be important for predicting ecosystem service provision from multi-species cover crop mixtures.