Effect of Decomposition Agent Dosage, Moisture Content, and Initial C/N Ratio on Decomposition of Rice Straw

Yaqi Zhu, Shan Wang, Yong Liu, Yinglong Chen, Khalil Kariman, Jinming Liang, Yuanming Wen, Dingzhi Zhou, Zhaohao Chen, Mu Zhang, Xiu Yi

Research output: Contribution to journalArticle

Abstract

In the present study, the effect of different Jinkuizi decomposition agent dosages (Factor A: A0, A0.5, and A1.0; %), moisture contents (Factor B: B50, B60, and B70; %), and initial C/N ratios (Factor C: C20, C22, and C25) on rice straw decomposition was investigated using an orthogonal test design, in order to find out the best initial conditions for decomposing straw and provide a scientific basis for decomposed straw returning to the fields. Decomposition indicators such as pH, germination index (GI), C/N
ratio, decomposing ratio (DR), dissolved organic carbon (DOC), and ultraviolet spectral parameters (SUVA280, E2/E3, and A226‒400) were analyzed. Results showed that during the decomposition period, the GI and DR values for all treatments gradually increased as the decomposition progressed. The C/N ratios for the A0B70C25 and A0.5B70C22 treatments continuously decreased, while those for the other treatments first increased and then decreased. The DOC contents for the A0B50C20 and A1.0B70C20 treatments first increased and
then decreased, while there was an increasing trend for the other treatments. The variation of aromatic structure and humification
degree of dissolved organic matter was well linked to the variations of ultraviolet spectral parameters obtained from the rice straw compost. At the end of the decomposition period, the pH, GI, and DR values (7.05, 34.9%, and 30.7%, respectively) declined dramatically, whereas the C/N ratio (25.7) was very high in the incompletely decomposed A0B50C20 treatment. For all the employed treatments (except A0B50C20), the pH values were found in accordance with the required standard of compost maturity (8.00‒9.00), while the higher GI values indicated low toxicity (≥50%) or fully decomposed state (≥80%). The C/N ratios for the A0B70C25, A0.5B70C22, and A1.0B60C25 (13.1, 14.4, and 16.4, respectively) treatments were consistent with the best-fit value (15.0), and the highest DR value (47.1%) was found in the A0.5B70C22 treatment. The GI value could be inferred from ultraviolet spectral parameter detection, which provided an alternative evaluation method for determining whether the rice straw compost was fully decomposed.
Under such controlled experimental conditions, the optimal initial requirements for rice straw decomposition were determined to be a decomposition agent dosage of 0.5%, moisture content of 70%, and initial C/N ratio of 25. Further analysis showed that the
decomposition agent dosage had the greatest influence on the DOC content; the moisture content had the greatest influences on the C/N ratio, DR, SUVA280, E2/E3, and A226‒400 values; and the initial C/N ratio had the greatest influences on the pH and GI values.
Original languageEnglish
Pages (from-to)601−611
JournalEcology and Environmental Sciences
Volume28
Issue number3
DOIs
Publication statusPublished - 1 Mar 2019

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