This study aimed to discern the effect of different levels of irrigation with reclaimed Water on soil enzyme activities and on the distribution of thermotolerant coliforms. The effects of two irrigation Water qualities (reclaimed Water and tap Water) and two irrigation levels (full irrigation and insufficient irrigation) on soil enzyme activity and distribution of thermotolerant coliforms were studied through indoor soil column irrigation. Results indicated that:① Reclaimed Water irrigation increased soil urease and invertase activity compared with tap Water under the same irrigation conditions. Compared with insufficient irrigation with reclaimed Water, full irrigation with reclaimed Water significantly increased soil invertase activity and deep soil catalase activity. ② At the same irrigation level, the number of thermotolerant coliforms in soil significantly increased with reclaimed Water irrigation. The number of thermotolerant coliforms in soil under full irrigation with reclaimed Water was significantly higher than with insufficient irrigation using reclaimed Water. The number of thermotolerant coliforms in surface soil of the four irrigated treatments was significantly higher than in the deep soil layer, and with progression of irrigation, the number of thermotolerant coliforms in the 0-60 cm soil layer decreased. ③ There was a significant positive correlation between the quantity of thermotolerant coliforms and the activity of soil urease and invertase, and between the quantity of thermotolerant coliforms and the activity of soil catalase. Reclaimed Water therefore promoted enzyme activity that can promote transformation of C and N in soil. Reasonable irrigation with reclaimed Water can therefore effectively control the number of thermotolerant coliforms in soil.
