Studies on Urease-producing Microorganisms, Urease Activity and Urea Efficiency in Paddy Soil

The investigation showed that the numbers of urease-producing microorganisms were identical with the urease activities in responding paddy soils whatever different seasons,soil type and the distribution of soil profile.The proportions of urease-producing populations among bacteria,actinomyces and fungi account for 32.5-85.5%,50-83% and 65-95% respectively.However,few of them showed high urease activity,and mostly were below 2.0 NH3-N mg/g· Protein·24hr · 37℃ To compare with the treatments of urea topdreasing and urea topdressing with azolla application,the urease activities in paddy soils of the treatments of deepplacement of urea ball fertilizer,and deepplacement of urea ball fertilizer with azolla were decreased.As a result,the urea efficiency was increased.