Abstract
Arsenic (As) contamination was used to stress ecosystem functioning and the activity of five soil enzymes were used to measure the level of stress: β-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 β-glucosidase increased the highest under aerobic conditions (30%–34%), ranging from 52.64–194.15 μg ρ-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 β-glucosidase, acid phosphatase, alkaline phosphatase and arylsulfatase can serve as potential indicators of soil biochemical functionality in As contaminated soils under study conditions.
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•Enzyme activities along with paddy soil As were affected by rice agroecosystems.•Aerobic system significantly enhanced the enzyme activities compared to anaerobic.•Amendments application improved all the enzyme activities.•Enzyme activities were inhibited with increasing paddy soil As concentrations.