The impact of Arsenic induced stress on soil enzyme activity in different rice agroecosystems

Arsenic (As) contamination was used to stress ecosystem functioning and the activity of five soil enzymes were used to measure the level of stress: beta-glucosidase, urease, acid phosphatase, alkaline phosphatase, and arylsulfatase. Two consecutive field experiments were conducted based on differences in rice agroecosystems during the monsoon (wet) and the post-monsoon (dry) seasons: one measured the impact of As stress on anaerobic rice agroecosystem and the other under aerobic; each receiving soil amendments (including organic manure, vermicompost, NPK, silicon, iron). Aerobic treatment significantly reduced soil As (P <0.05) as compared to anaerobic conditions. The activity of beta-glucosidase increased the highest under aerobic conditions (30%-34%), ranging from 52.64-194.15 mu g rho-nitrophenol g(-1) of dry soil h(-1) relative to anaerobic conditions. Enzyme activities also increased under aerobic conditions, ranging from 24%-29%, 21%-22%, 12%-18%, and 14%-16% for alkaline phosphatase, arylsulfatase, acid phosphatase and urease, respectively. The incorporation of organic manure under aerobic conditions resulted in significant increases in enzyme activities relative to control and NPK. Differences in As concentrations between each of the agroecosystem caused significant inhibitory effects on most soil enzyme activities; however, urease activity was not impacted. Principal Component Analysis (PCA) of enzyme activities indicated that urease activity had the lowest factor loading on PCA in wet and dry seasons. Overall, the aerobic system was better to strengthen soil ecosystem health by increasing enzyme activities, while the activity of beta-glucosidase, acid phosphatase, alkaline phosphatase and arylsulfatase can serve as potential indicators of soil biochemical functionality in As contaminated soils under study conditions. (C) 2022 Published by Elsevier B.V.

Automated summary

This study examined the impact of arsenic contamination on ecosystem functioning and soil enzyme activity. The results showed that aerobic conditions significantly reduced soil arsenic levels and increased enzyme activities. Organic manure amendment further enhanced enzyme activities under aerobic conditions. Differences in arsenic concentrations had inhibitory effects on most soil enzyme activities, except for urease activity.