Journal Article

The impacts of four potential bioenergy crops on soil carbon dynamics as shown by biomarker analyses and DRIFT spectroscopy

Masters, Michael D., Liang, Chao, DeLucia, Evan H., Kantola, Ilsa B., Zhu, Xuefeng

2018

Overview

Perennial bioenergy crops accumulate carbon (C) in soils through minimally disturbing management practices and large root inputs, but the mechanisms of microbial control over C dynamics under bioenergy crops have not been clarified. Root‐derived C inputs affect both soil microbial contribution to and degradation of soil organic matter resulting in differing soil organic carbon (SOC) concentrations, storage, and stabilities under different vegetation regimes. Here, we measured biomarker amino sugars and neutral sugars and used diffuse reflectance mid‐infrared Fourier transform spectroscopy (DRIFTS) to explore microbial C contributions, degradation ability, and SOC stability, respectively, under four potential bioenergy crops, M.×giganteus (Miscanthus × giganteus), switchgrass (Panicum virgatum L.), a mixed prairie, and a maize (Zea mays L.)–maize–soybean (Glycine max(L.) Merr.) (MMS) rotation over six growing seasons. Our results showed that SOC concentration (g/kg) increased by 10.6% in mixed prairie over the duration of this experiment and SOC storage (Mg/ha) increased by 17.0% and 15.6% in switchgrass and mixed prairie, respectively. Conversion of row crops to perennial grasses maintained SOC stability and increased bacterial residue contribution to SOC in M.×giganteus and switchgrass by 20.0% and 15.0%, respectively, after 6 years. Degradation of microbe‐derived labile SOC was increased in M.×giganteus, and degradation of both labile and stable SOC increased in MMS rotation. These results demonstrate that microbial communities under perennial grasses maintained SOC quality, while SOC quantity increased under switchgrass and mixed prairie. Annual MMS rotation displayed decreases in aspects of SOC quality without changes in SOC quantity. These findings have implications for understanding microbial control over soil C quantity and quality under land‐use shift from annual to perennial bioenergy cropping systems. Microbial substrate preference is speculated to be driven by labile carbon inputs and available nitrogen. The results from this study demonstrate optimal conditions for increasing soil organic carbon quantity and quality beyond a cessation of tillage include a diverse aboveground ecosystem, high belowground labile carbon inputs, and available nitrogen.

• Publisher: John Wiley & Sons, Inc
• Subject: amino sugars / Biodegradation / biomarker / Biomarkers / Carbon / Corn / Cropping systems / Crops / diffuse reflectance mid‐infrared Fourier transform spectroscopy / Energy crops / Fourier transforms / Glycine max / Grasses / Growing season / Land use / maize–maize–soybean rotation / Microbial activity / Microbial degradation / microbial residue / Microorganisms / Miscanthus giganteus / neutral sugars / Organic carbon / Organic matter / Organic soils / Panicum virgatum / perennial bioenergy crops / Perennial crops / Reflectance / Renewable energy / Rotation / Soil degradation / Soil dynamics / soil organic carbon decomposition / soil organic carbon stability / Soil organic matter / Soybeans / Spectroscopy / Spectrum analysis / Stability / Sugar / Zea mays