Diversification of perennial crop plantings may provide an array of ecosystem services, including increased yields due to decreased pathogen presence, facilitation, or niche-partitioning. However, understanding compatibility of perennial crop species in the presence of beneficial and potentially pathogenic soil biota in variable abiotic conditions is necessary to determine the sustainability of plantings. Here we performed a greenhouse experiment to assess monoculture and bi-culture performance of three perennial crop species: Thinopyrum intermedium (which produces the perennial grain Kernza®), alfalfa, and Silphium integrifolium. Seedlings were planted into sterile soil inoculated with whole soil conditioned by a long term monoculture of Kernza®, arbuscular mycorrhizal fungi (AMF) from a Kansas remnant prairie, or sterile soil. Pots were watered daily (wet) or every three days (dry). Aboveground biomass was harvested, separated to species, dried, and weighed after eight weeks of growth.
Results/Conclusions
Mixtures with Kernza® had positive overyielding, but the alfalfa and Silphium mixture did not. Yield per individual of Kernza® was greater with increased water availability, in mixture compared to monoculture, and in sterile compared to live whole soil. The identity (alfalfa or Silphium) of the other species in mixture did not impact Kernza® performance. Kernza® growth was greatest in mixtures with sterile whole soil in the absence of Kansas AMF. This occurred because alfalfa and Silphium produced very little biomass due to strong AMF dependency. Results suggest that the perennial grain Kernza® benefits from being planted in mixture due to strong intraspecific competition, and show the negative and positive impacts of soil biota on perennial crop species. This study reinforces the positive effects of increasing spatial crop diversity within perennial agriculture systems.