The influence of certain pesticides on soil respiration and urease activity | ||
Journal of Pest Control and Environmental Sciences | ||
Volume 14, Issue 2, December 2006, Pages 365-380 PDF (198.42 K) | ||
Document Type: Original Article | ||
DOI: 10.21608/jpces.2006.460770 | ||
Authors | ||
Ashraf E. Mostafa; A. A. Komeil; A. F. El-Aswad* ; M. I. Aly | ||
Pesticide Chemistry Dept., Faculty of Agriculture, Alexandria University | ||
Abstract | ||
The side effect of pesticides on soil microflora could be investigated by studies of microbial respiration and soil enzymes. The influence of the insecticide, chlorpyrifos; the fungicide mancozeb and the herbicide, glyphosate on soil respiration and soil urease activity, kinetic and inhibition was evaluated. Two common Egyptian soil types, clay loam and sandy clay loam soil with two concentrations of tested pesticides, recommended and three fold of recommended field rate were tested. The results indicated that the soil type was found to be the most effective factor on soil respiration. In contrast, the tested concentrations of pesticides did not affect soil respiration. The rate of soil respiration was more in the case of clay loam soil (Kafre El-Zyate soil) under different treatment than that in sandy clay loam soil (Borg El-Arab soil). According to the statistical analysis, the effect of each tested pesticide on urease activity did not change either with soil type or with pesticide concentrations. The optimum substrate and protein concentrations are 83 mM and 75 µg in the standard assay. Also, the optimum pH value is 6.7. Indirect proportionality between the incubation time and the velocity of urease reaction was recorded. The Michaelis Menten constant (Km) was 53.1 mM and the Vmax value was 434.78 µM hydrolyzed urea min-1. The Vmax values were 14.592, 18.727 and 10.10 µM min-1 for chlorpyrifos, mancozeb and glyphosate, respectively. Regarding the Ki values, all tested pesticides inhibited urease enzyme with the following ascending order; glyphosate < chlorpyrifos < mancozeb. | ||
Keywords | ||
Pesticides; soil respiration; soil urease; urease kinetic | ||
Statistics Article View: 1 PDF Download: 2 |