In effort to regain valuable ecosystem services, agricultural practices that incorporate perennial crops are being developed. Many plant candidates for perennial agroecosystems are derived from or closely related to indigenous perennial prairie species. Because many prairie species are highly dependent on arbuscular mycorrhizal (AM) fungi, it is likely that many perennial crops also rely on this relationship. Prairie reconstructions and perennial agricultural plantings typically follow massive disturbances, such as tillage, which have more disturbed and ineffective fungal communities. Therefore, the reintroduction of AM fungal communities may benefit both practices. We tested the benefits of AM fungi at different inoculation rates in a prairie reconstruction and perennial crop polyculture planting at the Land Institute Perennial Agricultural Project field station in Lawrence, Kansas. Plots were seeded with a diverse prairie mixture or planted in rows of perennial crops, including two varieties of Kernza®, Silphium integrifolium, Alfalfa, Lupine, Kura Clover, and a perennial hybrid of Sorghum. Cultured AM fungi from an unploughed, remnant prairie in Kansas were applied at eight mycorrhizal inoculation rates ranging from 0-3.7 cubic meters (0-1,000 gallons) per 4000 square meters. We collected data on prairie species seeded richness and abundance and crop species productivity, survival and seed set.
Results/Conclusions
Generally, we found that more mycorrhizal inocula was better; prairie richness and seeded abundance increased linearly with inoculation rate. We found that lower inoculation rates (those recommended by commercial mycorrhizal products) tended not to be significantly different from the controls whereas with the higher inoculation rates (those reported in the scientific literature as being effective), we found significantly greater richness and abundance of seeded prairie species. We found similar patterns for perennial crop species, as Silphium and alfalfa growth and Sorghum seed set increased linearly with mycorrhizal inocula input and these plants were most productive with the highest inoculation rates. These data demonstrate the value to using a holistic approach to restoration and the initiation of perennial polycultures that includes providing plants with beneficial microbiome components that they may be dependent on. Additionally, these data suggest that the inoculation rates recommended by commercial growers of mycorrhizal fungi may not be great enough to elicit beneficial effects in prairie reconstruction or in perennial plantings and that greater inocula application rates or alternative methods of introducing the mycorrhizal inocula may be needed.