Potential effects of laccase on the formation and accumulation of Fe-OM complexes in coastal saline paddy soil under straw and nitrogen fertilization

ABSTRACT

The bindings of organic matter (OM) with iron (Fe-OM complexes) are important for soil carbon (C) sequestration. Our objective was to evaluate the role of laccase in the formation of Fe-OM complexes in a coastal saline paddy soil. The experiment included two factors: (1) two nitrogen (N) levels, 255 (N1) and 400 (N2) kg N ha⁻¹; (2) three straw levels: 0 (S0), 4500 (S1) and 9000 (S2) kg C ha⁻¹. The results showed that the combined application of straw and N fertilizer increased the content of Fe-bound OC and laccase activity, both of which were the highest in N1S1 treatment, which was 7.48% and 0.58 μmol g⁻¹ h⁻¹, respectively. The content of Fe-bound OC was positively correlated with laccase activity, Fe_am content and soil moisture content, but negatively correlated with pH. Both Fe-bound OC and laccase activity were positively correlated with aliphatic functional groups and hydroxyl or amidogen, while both were negatively correlated with aromatic functional groups. Therefore, laccase might promote the formation of Fe-bound OC by changing the chemical structure of OC. In addition, the combined application of straw and N fertilizer could change laccase activity by changing microbial community structure (e.g. Chloroflexi, Ascomycetes and Zygomycota).

KEYWORDS:

• Coastal saline paddy soil
• carbon sequestration
• laccase
• soil organic carbon
• Fe-bound OC

Acknowledgements

The work was financially supported by the National Key R&D Program of China (2021YFD1900901-06), the Modern Agricultural Technology System Innovation Team of Paddy of Shandong (SDAIT-17-05), the Natural Science Foundation of Shandong (ZR2020MC154) and Postgraduate Innovation Program of Qingdao Agricultural University (QNYCX20039). We thank Professor Timothy George for his critical reading and revision on the manuscript and Dr. Zhang Lin for his suggestions on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).