Nutrient Source and Tillage Effects on Maize: II. Yield, Soil Carbon, and Carbon Dioxide Emissions

Core Ideas Industrial biotechnology waste as a soil amendment approximates farmer practice yields. Applying waste amendments significantly increased soil organic C compared with farmer practice. Using waste nutrients for agriculture and soil organic matter improves sustainability. Reuse of industrial biotechnology by‐products has become an important component of circular bio‐economies whereby nutrient‐rich wastes are returned to agricultural land to improve soil fertility and crop productivity. Heat‐inactivated spent microbial biomass (SMB) from the production of 1,3‐propanediol is an industrial fermentation by‐product with nutrients that could replace or supplement conventional fertilizers. Our objectives were to determine if SMB utilization as a soil amendment in agriculture could generate environmental benefits while meeting farmer yield expectations and assess the impact of SMB application on CO2 emissions. This study examined the replacement of typical farmer fertilizer practices with the application of SMB. In addition to yellow dent maize (Zea mays L. var. indentata) grain yield and aboveground biomass, soil organic carbon (SOC) was measured. The eddy covariance (EC) micrometeorological method was used to measure CO2 flux. Overall maize yields were positively correlated with increasing application rates of SMB. After two SMB applications, SOC increased by 45% on the SMB plot as compared with an increase of 11% on the farmer practice plot. The SMB‐treated plot also emitted more CO2 (794 g CO2 m−2 yr−1) compared with the farmer practice treatment (274 g CO2 m−2 yr−1). Results from this study provide information on the efficacy of waste product nutrient cycling in the soil–plant ecosystem that could improve productivity and sustainability.