Decomposition Dynamics and Changes in Chemical Composition of Wheat Straw Residue under Anaerobic and Aerobic Conditions

Abstract

Soil aeration is a crucial factor that regulates crop residue decomposition, and the chemical composition of decomposing crop residues may change the forms and availability of soil nutrients, such as N and P. However, to date, differences in the chemical composition of crop straw residues after incorporation into soil and during its decomposition under anaerobic vs. aerobic conditions have not been well documented. The objective of the present study was to assess changes in the C-containing functional groups of wheat straw residue during its decomposition in anaerobic and aerobic environments. A 12-month incubation experiment was carried out to investigate the temporal variations of mass, carbon, and nitrogen loss, as well as changes in the chemical composition of wheat (Triticum aestivum L) straw residues under anaerobic and aerobic conditions by measuring C-containing functional groups using solid state nuclear magnetic resonance (NMR) spectroscopy. The residual mass, carbon content, and nitrogen content of the straw residue sharply declined during the initial 3 months, and then slowly decreased during the last incubation period from 3 to 12 months. The decomposition rate constant (k) for mass loss under aerobic conditions (0.022 d-1) was higher than that under anaerobic conditions (0.014 d-1). The residual mass percentage of cellulose and hemicellulose in the wheat straw gradually declined, whereas that of lignin gradually increased during the entire 12-month incubation period. The NMR spectra of C-containing functional groups in the decomposing straw under both aerobic and anaerobic conditions were similar at the beginning of the incubation as well as at 1 month, 6 months, and 12 months. The main alterations in C-containing functional groups during the decomposition of wheat straw were a decrease in the relative abundances of O-alkyl C and an increase in the relative abundances of alkyl C, aromatic C and COO/N-C = O functional groups. The NMR signals of alkyl C and aromatic C in decomposing wheat straw residues under anaerobic condition were higher than those under aerobic conditions. The higher mass percentages of lignin and the higher signals of aromatic C and alkyl C functional groups in decomposing wheat residues under anaerobic conditions than under aerobic conditions were due to the slower decomposition rates of aryl C and alkyl C in wheat straw residues under anaerobic conditions.

Genetic and environmental control of lignin biosynthesis and C emission from crop stover

“…In a population consisting of 495 genotypes measured over two years, we found that genotype could explain 23% of variation in C emission and broad-sense heritability was 0.25. The substantial variation observed in this study for C emission across environments agrees with observations from studies of other species Yanni et al, 2011, Gao et al, 2016.…”

Methane emissions from paddy grown on mineral soil over peat in central Hokkaido, Japan

“…Eh changes occur more rapidly in flooded rice paddy fields in the presence of readily decomposable rice straw [32]. The lignin level in soybean stover (11.9%) is higher than in rice straw (7.3%) [33], and high lignin content slows the decomposition of organic matter [34]. Moreover, growing an upland crop in rotation with flooded rice can cause sufficient aeration of the soil to increase Eh periodically [30], which, in turn, may reduce CH4 emissions.…”

Decomposition and nutrients cycling of residual biomass from integrated crop-livestock system

“…Teixeira et al (2011) evaluated the decomposition and release of nutrients from the aerial part of millet and sorghum plants, found half-life (t½), 98 days for millet, and 96 days for sorghum. However, Gao et al (2016) evaluated the decomposition of wheat straw in anaerobic and aerobic conditions, found a longer half-life (t ½), 122 days, under anaerobic conditions, when compared to aerobic conditions, 73 days. In 2015, the remaining biomass was lower, which also had a shorter half-life (t ½).…”