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

Abstract

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.

Nutrient Source and Tillage Effects on Maize: I. Micrometeorological Methods for Measuring Carbon Dioxide Emissions

“…The field site was split into two areas, both seeded with maize ( Zea mays L. var. indentata ), but with one treated with an application of spent microbial biomass (SMB) as explained in Part 2 of this series (O'Dell et al, 2019). This treatment was applied to the northern 8.4‐ha area.…”

“…The accompanying reference field to the south (10.3 ha) received mineral fertilizer consistent with a typical farmer practice (FP) in place of the SMB. (The reader is referred to O'Dell et al, 2019 for a detailed description of the treatment applications, including application timing and nutrient contents of both SMB and FP applications. )…”

“…The study site was a 19.1 ha farm in Loudon, TN (35.708° N, -84.373° W, 274 m asl) with a slope of 2 to 12%, as described in Part 2 of this series (O'Dell et al, 2019). The climate is classified as humid subtropical (Cfa) according to Köppen's climate classification with mean annual rainfall of 1245 mm (NOAA, 2019).…”