Effect of waterlogged and aerobic incubation on enzyme activities in paddy soil

An incubation experiment with soil water content treatments of 0.15 (W1), 0.20 (W2), and 0.40 (W3) g g(-1) soil was carried out for two months to investigate the activities of important enzymes involved in C, N, P, and S cycling in a paddy soil from the Taihu Lake region, China, under waterlogged and aerobic conditions. Compared with air-dried soil, waterlogging resulted in a significant decrease (P <= 0.05) of fluorescein diacetate (FDA) and beta-D-glucosidase activities, and this effect was enhanced with increasing waterlogging time. Waterlogging also significantly inhibited (P <= 0.05) arylsulfatase as well as alkaline and acid phosphatase activities, but did not decrease the activities with the increase in waterlogging time. Short-term waterlogging did not affect urease activity, but prolonged waterlogging decreased it markedly. In contrast, the aerobic incubation (W1 and W2 treatments) significantly increased (P <= 0.05) FDA, alkaline phosphatase, and beta-D-glucosidase activities. With aerobic treatments the activities of FDA and alkaline phosphatase increased with incubation time, whereas beta-D-glucosidase activity decreased. A significant difference (P <= 0.05) was usually observed between the W1 and W2 treatments for the activities of FDA as well as alkaline and acid phosphatase; however, beta-D-glucosidase and urease were usually not significant (P <= 0.05). No activity differences were observed between waterlogging and aerobic incubation for arylsulfatase and urease.