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Vertical distribution of soil organic carbon and dissolved organic carbon in reddish paddy soil under long-term green manure utilization
XIA Wenjian, QIN Wenjing, LIU Jia, CHEN Xiaofen, ZHANG Lifang, CAO Weidong, XU Changxu, CHEN Jingrui
2020, 32(5):
878-885.
DOI: 10.3969/j.issn.1004-1524.2020.05.16
The objective of this study was to evaluate the effects of long-term application of green manure on the distribution of soil organic carbon (SOC) and dissolved organic carbon (DOC) in reddish paddy soil. Soil samples were collected from the 8 years' long-term experiments located in Fengcheng City, Jiangxi Province. Four treatments were carried out in the experiment: CK (no fertilizer), F (only chemical fertilizers), M (only green manure), F+M (green manure plus chemical fertilizers). The green manure was Chinese milk vetch (Astragalus sinicus L.). The vertical distribution of SOC and DOC in soil layers and the quantitative relationship of SOC and DOC were investigated. The results showed that, the variation of SOC and DOC contents with soil depths could be described by S-function in early rice and late rice season. The determination coefficients of function equations were 0.928-0.966 and 0.876-0.975, which reached significant level at P<0.01. The application of chemical fertilizers or green manure (treatment F, M, and F+M) affected SOC and DOC contents in the topsoil (0-20 cm). There was no significant difference in SOC and DOC in deep soil (>20 cm) within different treatments. Green manure treatments (F+M and M) significantly (P<0.05) increased SOC and DOC in topsoil, while chemical fertilizers treatment (F) only significantly (P<0.05) increased the SOC content in topsoil. Compared with CK, the contents of SOC in topsoil treated with M, F and F+M in early rice season were significantly (P<0.05) increased by 51.1%, 80.9%, 92.8%, respectively, and the contents of DOC in topsoil treated with M and F+M in early rice season were significantly (P<0.05) increased by 12.9% and 46.2%, respectively; while the contents of SOC and DOC in topsoil treated with M, F and F+M in late rice season were significantly (P<0.05) increased by 66.6%, 81.3%, 81.2% and 37.1%, 10.8%, 45.2%, respectively. The DOC content of topsoil increased linearly with SOC, and the increase ratio of DOC with SOC in late rice season was higher than that in early rice season. The long-term application of chemical fertilizers reduced DOC/SOC, yet green manure could mitigate DOC/SOC decrease. Green manure could not only increase soil organic carbon, but also benefit the stability of soil organic carbon ecological function.
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