Aboveground and belowground responses to cyanobacterial biofertilizer supplement in a semi-arid, perennial bioenergy cropping system

The need for sustainable agricultural practices to meet the food, feed, and fuel demands of a growing global population while reducing detrimental environmental impacts has driven research in multi-faceted approaches to agricultural sustainability. Perennial cropping systems and microbial biofertilizer supplements are two emerging strategies to increase agricultural sustainability that are studied in tandem for the first time in this study. During the establishment phase of a perennial switchgrass stand in SW Montana, USA, we supplemented synthetic fertilization with a nitrogen-fixing cyanobacterial biofertilizer (CBF) and were able to maintain aboveground crop productivity in comparison to a synthetic only (urea) fertilizer treatment. Soil chemical analysis conducted at the end of the growing season revealed that late-season nitrogen availability in CBF-supplemented field plots increased relative to urea-only plots. High-throughput sequencing of bacterial/archaeal and fungal communities suggested fine-scale responses of the microbial community and sensitivity to fertilization among arbuscular mycorrhizal fungi, Planctomycetes, Proteobacteria, and Actinobacteria. Given their critical role in plant productivity and soil nutrient cycling, soil microbiome monitoring is vital to understand the impacts of implementation of alternative agricultural practices on soil health.

Automated summary

This study investigates the simultaneous use of perennial cropping systems and microbial biofertilizer supplements as emerging strategies to increase agricultural sustainability. Results show that supplementing synthetic fertilization with a nitrogen-fixing cyanobacterial biofertilizer during the establishment phase of a perennial switchgrass stand in SW Montana, USA, can maintain aboveground crop productivity and increase late-season nitrogen availability in the soil. High-throughput sequencing of microbial communities revealed fine-scale responses and sensitivities to fertilization among different bacterial/archaeal and fungal groups. Monitoring soil microbiome is crucial to understand the impacts of alternative agricultural practices on soil health.