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|a Municipal sewage sludge (MSS) disposal through land application was a cost-effective option for improving soil quality. It is inconsistent about the effects of MSS addition on the variations of soil enzyme activities and stoichiometries, which have been frequently used as indicators of soil quality. A laboratory incubation experiment was conducted for 60 days with six treatments: non-amended soil (CK), soil amended with synthetic fertilizer (N or P addition), and different doses (5%, 10%, and 15%) of MSS. Soil samples were collected after 1, 2, 3, 5, 7, 10, 15, 30, 45, and 60 days of incubation, and C-, N-, and P-acquiring enzyme activities (β-glucosidase [BG], N-acetyl-glucosaminidase [NAG], L-leucine aminopoptidase [LAP], and phosphatase [AP]) were determined and enzyme stoichiometries were calculated. BG, NAG+LAP, and AP activities logarithmically increased with incubation time. The daily variation of BG, NAG+LAP, and AP activities first increased and then decreased with incubation time, with the highest value on the 7th day incubation. Compared with CK, the cumulative enzyme activities increased by 323.8-389.8% in the 15% MSS addition treatment, whereas those under the N and P treatments significantly decreased by 18.0%-51.4% and 31.8%-53.0%, respectively. Enzyme C:N decreased but C:P and N:P increased during incubation with MSS addition. However, synthetic N and P addition increased the enzyme C:N and C:P but decreased enzyme N:P. These results indicated that N and P addition decreased the enzyme activities, and MSS addition significantly increased the secreting of enzymes and would be better for alleviating soil C and N limitations. © 2022, HARD Publishing Company. All rights reserved.
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