Urease activity and inhibition in flooded soil systems

Perdas de nitrogênio por volatilização de amônia e resposta do arroz irrigado à aplicação de ureia tratada com o inibidor de urease NBPT

“…De forma geral, as perdas de nitrogênio por volatilização de amônia decorrem de adubações que promovem elevadas concentrações de N amoniacal na camada superficial do solo, particularmente em razão da ausência ou incorporação ineficiente do fertilizante (PHONGPAN et al, 1995), sendo mais intensas quando doses elevadas do nutriente são aplicadas nos estádios iniciais de desenvolvimento da cultura (VLEK et al, 1980), condição que está se intensificando nos cultivos de arroz irrigado no Rio Grande do Sul.…”

Dynamics of ammonia volatilization losses in wetland soil following the broadcasting application of urea amended with phenyl phosphorodiamedate

“…The slow decline in the floodwater urea concentration was probably due to the insufficient amount of urease in the floodwater of the soil under study. Urea largely remained nonhydrolyzed in the floodwater which exhibited a low urease activity (VLEK et al 1980). Since the major site of urea hydrolysis activity is lower in floodwater than in the underlying soil surface (DELAUNE and PATRICK 1970;VLEK et al 1980;SIMPSON et aL 1984), this may have resulted in the persistence of large amounts of nonhydrolyzed urea in the floodwater of the urea + PPD treatment.…”

“…Since the major site of urea hydrolysis activity is lower in floodwater than in the underlying soil surface (DELAUNE and PATRICK 1970;VLEK et al 1980;SIMPSON et aL 1984), this may have resulted in the persistence of large amounts of nonhydrolyzed urea in the floodwater of the urea + PPD treatment. The inhibition of urea hydrolysis in the floodwater after the broadcasting of urea with PPD in the present study took a longer time than in similar greenhouse experiments reported by other workers (VLEK et al 1980;BYRNES et aL 1983). This may partly be caused by the differences in the soil urease activity, rate of urea application and floodwater depth.…”

“…The technological approach to increase the efficiency of the use of urea fertilizer in flooded soils which consists of the inhibition of the urease activity for minimizing the loss has received considerable attention in recent years (VLEK et al 1980). VLEK et al (1980) showed that the urease inhibitor, phenyl phosphorodiamidate (PPD) effectively inhibited the urease activity, delayed urea hydrolysis, and reduced the buildup of ammoniacal N in floodwater.…”

Effects of phosphoroamides on transformations of urea nitrogen in soil

“…This research has indicated that several phosphoroamides have potential value for retarding urea hydrolysis in soil (Held et al, 1976b;Matzel et al, 1978a;1979;Heber et al, 1979;Vlek et al, 1980;Byrnes et al, 1983;Kampfe et al, 1983;Martens and Bremner, 1984a;1984b;Chai and Bremner, 1985), but no information is available concerning the effects of these compounds on nitrification, denitrification, or mineralization of organic nitrogen in soil, and such information is clearly needed to assess the potential value of phosphoroamides for control of urea N transformations in soil.…”