Main content area

Response of soil organic carbon fractions to increasing rates of crop residue return in a wheat–maize cropping system in north-central China

Zhao, S. C., Huang, S. W., Qiu, S. J., He, P.
Soil research 2018 v.56 no.8 pp. 856-864
carbon sequestration, corn, crop residues, cropping systems, fertilizer application, field experimentation, labile carbon, microbial biomass, mineral fertilizers, soil, soil microorganisms, water solubility, China
Labile organic carbon (C) in soil can act as a sensitive indicator of its quality, and understanding its response to crop residue incorporation rates is critical to increase soil C storage by residue return in conjunction with chemical fertilisation. A 30-year field experiment was carried out to study the effects of various rates of maize residue return on soil organic C fractions in the presence of chemical fertilisers in a wheat–maize cropping system in north-central China. Studies included a no-fertiliser and no-residues control (CK) and maize residue return at rates of 0 (S0), 2250 (S1), 4500 (S2), and 9000kg ha−1 (S3) using chemical fertilisers. Soil total organic C (TOC) and labile organic C fractions were determined. The S0 treatment increased soil microbial biomass C (MBC), KMnO4-oxidisable C (KMnO4-C), and TOC, but did not change water-soluble organic C (WSOC), light fraction organic C (LFOC), and particulate organic C (POC), relative to CK. All organic C fractions did not differ between S0 and S1; however, S2–S3 increased MBC, WSOC, LFOC, POC, KMnO4-C, and TOC by 31.8–41.0%, 17.7–28.6%, 33.9–81.3%, 35.3–82.4%, 19.3–42.8%, and 9.7–20.4% compared with S0 respectively. The KMnO4-C had the highest correlation with TOC, with LFOC and POC showing higher sensitivity to different residue-return rates. Redundancy analysis showed that LFOC, POC, and KMnO4-C were mainly affected by residue-C and root-C, while MBC was closely correlated with rhizodeposition-C levels. Overall, low rates of residue return did not affect soil labile organic C and TOC, with they only started to increase significantly when annual residue return exceeded 4500kg ha−1 under chemical fertilisation; and the rate of increase for labile organic C was found to be higher than for non-labile C as residue inputs were increased.