Land Equivalent Ratio and Crop Biomass Evenness in Three Cover Crop Bicultures in the Northeastern USA
Date:
Nguyen, H. T. X., Smith, R. G., Boniface, H., Bybee-Finley, K. A., Darby, H. M., Duiker, S. W., Hashemi, M., Hirsh, S. M., Krezinski, I., Mallory, E. B., Mazzone, T. R., Mirsky, S. B., Molloy, T., Siller, A., Thapa, R., Tully, K., VanGessel, M. J., Wallace, J. M., Warren, N. D., Wayman, S., & Ryan, M. R.
Cover crop mixtures are popular with farmers seeking to broaden ecosystem services over single species. Understanding the performance of individual species in mixtures is important for optimizing resource partitioning and biomass production. A completely randomized field experiment was conducted across six sites in the northeastern USA in 2020-2021 that compared three cover crop species grown in monocultures and in bicultures: 1) cereal rye, 2) hairy vetch, and 3) forage rape. Land equivalent ratios (LER) and partial LERs were calculated to assess complementarity and Pielou’s evenness to assess the relative abundance of component species in mixtures. Results show that species varied in their competitive interactions, with hairy vetch and forage rape sometimes producing higher biomass when grown in mixtures compared to when they were grown separately, whereas cereal rye producing higher biomass and tended to suppress the growth of the other species when grown in mixtures. Results also show a positive correlation of biomass evenness index and total LER. Environmental conditions across sites also influenced cover crop performance and competitive interactions, indicating the optimal mixtures may vary by site.