The experiments conducted in fifteen small compartments with five different urae levels to dry soil in rice tiller for five days. The experiment results showed that urease activity had no obvious variance and the trend increased slowly. Nitrate reductase activity decrease quickly

and hydroxyamine reductase activity fluctuated

in addition we almost couldn't get the nitrate reductase activty in soil drying. The concentrate of ammonium-N fluctuated in soil surfaceand decrease as the delay of soil drying. The concentration of nitrate-N increased continuously in soil surface

which resulted in nitrate leaching to groundwater after rewetting. If soil was fertilized more urea mass

then the mineralizable N content was higher in soil surface. The aims of soil drying were that reduce the soil water content

advanced soil redox potention(Eh) and improved the conditions of soil aerating.