Biochemical stabilization of soil organic matter in straw-amended, anaerobic and aerobic soils

Xi Chen; Yujun Xu; Hong-Jian Gao; Jingdong Mao; Wenying Chu; Michael L Thompson

doi:10.1016/j.scitotenv.2017.12.293

Biochemical stabilization of soil organic matter in straw-amended, anaerobic and aerobic soils

Sci Total Environ. 2018 Jun 1:625:1065-1073. doi: 10.1016/j.scitotenv.2017.12.293. Epub 2018 Jan 12.

Authors

Xi Chen¹, Yujun Xu¹, Hong-Jian Gao², Jingdong Mao³, Wenying Chu³, Michael L Thompson⁴

Affiliations

¹ Anhui Province Key Laboratory of Farmland Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China.
² Anhui Province Key Laboratory of Farmland Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China; State Key Lab of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei 230036, China. Electronic address: hjgao@ahau.edu.cn.
³ Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529, USA.
⁴ Agronomy Department, Iowa State University, Ames, IA 50011, USA.

PMID: 29996403
DOI: 10.1016/j.scitotenv.2017.12.293

Abstract

Crop straw incorporation is a useful approach for increasing the quantity and changing the chemical composition of soil organic matter (SOM). This process is influenced by soil aeration. The present study investigated the stability of whole SOM, particulate organic matter (POM) and mineral-associated organic matter (MinOM) fractions with wheat straw amendment under aerobic and anaerobic conditions over a 12-month incubation period. Solid-state nuclear magnetic resonance and Fourier transform infrared spectroscopy were used to analyze the chemical composition of whole SOM, POM and MinOM fractions. The decomposition rate of wheat straw was lower under anaerobic than under aerobic conditions (0.014 vs. 0.020day^-1). Wheat straw incorporation increased the original soil organic carbon content (7.4g kg^-1) under both aerobic (up to 10.2g·kg^-1) and anaerobic (up to 10.3g·kg^-1) conditions, but the content of mineral-associated organic carbon (MinOC) under aerobic condition (7.0g·kg^-1) was significantly larger than that under anaerobic condition (4.9g·kg^-1). The proportion of alkyl carbon (C) in SOM, POM and MinOM fractions was greater under anaerobic than under aerobic conditions, while the opposite was true for the proportion of O-alkyl C of SOM and POM and MinOM fractions. A/O-A indices (i.e., the ratio of alkyl C to O-alkyl C) of whole SOM, POM and MinOM were higher under anaerobic than under aerobic conditions. We conclude that wheat straw incorporation resulted in the enrichment of alkyl C in the POM and MinOM fractions under anaerobic conditions, and thus improved the stability of SOM. In this way, the decomposition of crop residue influenced SOM structural chemistry at the molecular level.

Keywords: Alkyl C/O-alkyl C ratio; FTIR spectroscopy; Mineral-associated organic matter; NMR spectroscopy; Particulate organic matter; Soil organic matter.