Urease activity and urea hydrolysis in tropical flooded soil unplanted or planted to rice

Hydrolysis of urea associated with different component parts (surface and s ubsurface soil from unplanted and planted fields and standing water) of tro pical flooded rice soil was investigated. Urea hydrolysis followed a first- order kinetics with surface soil having the highest urease activity followe d by subsurface soil and flood water. Urea hydrolysis varied with the crop growth stage and was more pronounced at tillering and panicle stages under greenhouse conditions and at maturity stage under field conditions. A certa in degree of cultivar variation on urease activity at both surface and subs urface soil was also noticed. Urea hydrolysis was considerably higher in so ils from green manure amended field plots than that of control and urea ame nded plots. Results indicate that addition of green manure to a flooded soi l, while increasing microbial activity, could also enhance urea hydrolysis. (C) 1999 Society of Chemical Industry.