THE EFFECT OF PHENYL PHOSPHORODIAMIDATE ON UREASE ACTIVITY AND AMMONIA VOLATILIZATION IN FLOODED RICE

The behaviour of urease activity, ammoniacal N concentrations and pH in flood water and that of ammonia flux was investigated in a waterlogged soil either in the presence or in the absence of rice and with three different treatment (control, urea and urea+phenyl phosphorodiamidate). In the presence of the phenyl phosphorodiamidate (PPD), that is a urease inhibitor, increases in ammoniacal N concentrations and in ammonia evolution were delayed but not eliminated. The degradation and/or the inactivation of PPD might have occurred, thus removing the inhibition of the enzyme activity.