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Pakistan Journal of Biological Sciences
Year: 2005  |  Volume: 8  |  Issue: 4  |  Page No.: 606 - 613

Effect of 3,4-dimethylpyrazole Phosphate on Some Microbial Processes in Soil

F. Azam and C. Mueller    

Abstract: Laboratory incubation experiments were conducted to study the effect of 3,4-dimethylpyrazole phosphate (DMPP) on I) nitrification, ii) N mineralization potential of the soil, iii) immobilization-remineralization of N and iv) respiratory activity of the soil as well as N2O emissions. The inhibitor was applied at 0.35 to 17.5 mg kg-1 soil in different experiments and the incubation carried out at 25°C for variable lengths of time depending upon the nature of experiment. As expected, the process of nitrification slowed down in the presence of DMPP, rate of nitrification being slower at higher levels of the inhibitor. Measurable quantities of NO2- were found only during the first 3 days of incubation with DMPP having a negligible effect. Potentially mineralizable N showed a small but significant increase in the presence of DMPP i.e., an average of 11 and 9 mg kg-1 NH4+-N accumulating in treated and untreated soil samples, respectively, during the first week of incubation. As expected, only 10% of the NO3--N present initially was recovered after one week and ca 5% at the end of 2nd week of incubation suggesting significant losses, DMPP had a negligible effect on disappearance of NO3-. Immobilization of NH4+-N and NO3--N in glucose amended soil was significantly retarded by DMPP, the effect being more at higher than recommended concentrations. Immobilization of NO3--N was retarded more than that of NH4+-N suggesting that the immobilization of two forms of N was affected differently by DMPP. Net accumulation of mineral N (remineralization) was slower in DMPP-treated soil. The flux of N2O and respiratory activity (loss of CO2 and consumption of O2) decreased in the presence of DMPP.

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