Quantifying the roles of intra- and interspecific diversification strategies in forage cropping systems

Authors: Bybee-Finley, Kristine; MENALLED, URIEL - Cornell University; PELZER, CHRISTOPHER - Cornell University; RYAN, MATTHEW - Cornell University; DARBY, HEATHER - University Of Vermont; RUHL, LINDSEY - University Of Vermont; WARREN, NICK - University Of New Hampshire; LOUNSBURY, NATALIE - University Of New Hampshire; SMITH, RICH - University Of New Hampshire

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2023
Publication Date: 10/15/2023
Citation: Bybee-Finley, K.A., Menalled, U., Pelzer, C., Ryan, M.R., Darby, H., Ruhl, L., Warren, N., Lounsbury, N., Smith, R. 2023. Quantifying the roles of intra- and interspecific diversification strategies in forage cropping systems. Agricultural Systems. https://doi.org/10.1016/j.fcr.2023.109036.
DOI: https://doi.org/10.1016/j.fcr.2023.109036

Interpretive Summary: Planting mixtures of crops or varieties of crops together is a strategy for improving productivity and resilience of cropping systems in the face of climate change. We compared multiple strategies of making mixtures for annual and perennial forage cropping systems for 3 years in NY, NH, and VT. We examined yield, yield per seed cost, weed biomass, forage quality, and yield stability for the different strategies. Effects of the diversity strategies depended on crop type, site, and year. On average, yield of winter annuals was 12% greater in the mixture of different species versus the control. Weed biomass in the summer annuals was 36% lower in the mixture of crops and varieties compared to the control. In perennial systems, yield was 25% greater and weed biomass was an order of magnitude lower in the mixture of crops and varieties compared to the control. Stability analysis of yields across growing conditions showed that perennial crops yields were consistently greater in the mixture of crops and varieties compared to the control. However, yield stability analysis of summer annuals showed that yields of the mixture of crops and varieties were greater than yields of the control in low-yielding environments (20th percentile), illustrating a benefit of diversity in poor growing conditions. Strategically selecting species and varieties could further enhance the benefits of cropping system diversification. This information will be useful for scientists and extension specialists developing species and trait compatibility in mixtures and appropriate seeding rates to optimize production.

Technical Abstract: Cropping system diversification via intercropping is a strategy for improving productivity and enhancing the resilience of forage production systems in the face of climate change. We compared three strategies to increasing cropping system diversity via intercropping in both double-cropped three-year annual forage crop rotations and perennial forages in experiments conducted in New York, New Hampshire, and Vermont, USA. Three diversification strategies, (1) increase crop cultivar diversity (hereafter “Conspecific”), (2) increase crop species diversity (hereafter “Heterospecific”), and (3) increase both cultivar and species diversities (hereafter “High”), were compared against a control in which a single cultivar of a single species was grown (“Low”). Measured responses to diversification strategies included yield, yield per seed cost, weed biomass, forage quality, and yield stability. Effects of the diversity strategies depended on crop type, site, and year. When pooled over sites and years, yield of winter annuals was 12% greater in the Heterospecific treatment compared to the Low treatment. Weed biomass in the summer annuals was 36% lower in the High compared to the Low treatment. In perennial systems, yield was 25% greater and weed biomass was an order of magnitude lower in the High treatment compared to the Low treatment. Stability analysis of yields across growing conditions showed that perennial crops yields were consistently greater in the High treatment compared to the Low treatment. However, yield stability analysis of summer annuals showed that yields of the High treatment were greater than yields of the Low treatment in low-yielding environments (20th percentile), illustrating a benefit of diversity in poor growing conditions. Strategically selecting species and varieties for specific traits that maximize both functional and response diversity could further enhance the benefits of cropping system diversification. Future research should aim to develop guidelines for species and trait compatibility in mixtures and appropriate seeding rates to optimize production.