Abstract:Three ten-year fertilization experiments indicate the increment of protease, urease,invertase, phosphatase and hydrogen peroxidase activities in soil by organic-inorganic fertilization. Similarly, the contents of organic matter and nitrogen as well as phosphorus were increased by the fertilization of organic manure mixed with chemical fertilizers together. Positive correlation were found between the activities of protease. ureas and invertase and the contents of NH4+-N and organic matter, also phosphatase and the concentrations of available P and organic matter in soil as well. Thus, it seems reasonable to suggest that a suitable soil environment for crop growth could be produced by long-term fertilization of organic manure supplied with chemical fertilizers. Moreover, the activities of protease, urease and invertase in soil were decreased as rice growing in. contrast to phosphatase which was observed to be highest in the periods of jointing and heading as compared to those in tillering and mature. There also existed positive correlation between the activities of enzymes and the mobilizations of nitrogen and phosphorus in soil in rice growing period.