Utilization of spent microbial biomass as an alternative crop nitrogen source

Abstract

Spent microbial biomass (SMB), a nutrient-rich co-product of industrial white biotechnology processes, is produced in substantial quantities alongside high-value products and most often disposed of in landfills or incinerated. Alternatively, SMB could be reused as a land-applied N source in agricultural crop production, reducing the environmental and economic footprint of synthetic fertilizers. This research compares SMB applied at different rates to current farmer practice (FP) fertilizer use in tall fescue (Festuca arundinacea Schreb.) and corn (Zea mays L.) production on a Dewey silty clay in Lenoir City, TN. The effect of SMB on tall fescue was measured over three harvests through plant biomass production, crop N status using the normalized difference vegetation index (NDVI), and forage quality by near-infrared reflectance spectroscopy (NIRS). Corn productivity was measured by crop height, leaf chlorophyll content using a handheld meter, and grain yield. Tall fescue data showed the mineralization and release of SMB N over time compared with the rapidly available fertilizer N, and the highest SMB application rate in tall fescue was not statistically different from the FP in plant biomass, leaf NDVI, or any measured forage quality parameters. Despite differences in corn leaf chlorophyll contents between SMB and fertilizer treatments during the growing season, no differences in final grain yields were found. This research substantiates the potential of SMB as a soil N amendment from a nutrient source and yield perspective. Additional studies are needed to understand SMB mineralization rates and to confirm the material’s nutrient contribution to crop production.