Effect of some agrochemicals on certain soil biological and biochemical characteristics
2002
Subhani, A. (Soil and Water Conservation Research Inst., Chakwal (Pakistan)) | Chang-Yong, H. | Iqbal, M.N. | Ahmad, M.J.
Laboratory incubation experiments were conducted to elucidate the impact of various agro-chemicals (N fertilizer, pesticides) on a paddy field soil health under controlled moisture (flooded soil) and temperature (25 degree centigrade) conditions. The fertilizer (urea) was applied at the rate of 0, 25, 50, 100, 200, and 400 mug N g-1 soil and pesticide (insecticide, herbicide, fungicide) at the rate of 0, 0.5 FR (field rate), 1 FR, 5 FR, and 10 FR. The electron transport system (ETS)/Dehydrogenase activity displayed a negative correlation with pesticides concentrations, and the activity affected adversely as the concentration of the pesticides was increased. The higher doses, 5 and 10 field rates, of pesticides significantly inhibited ETS activity, while lower rates failed to produce any marked effect against the control. The relative toxicity of pesticides in decreasing the ETS activity was in the order. insecticide greater than fungicide greater than herbicide, irrespective of their rates of application. The fertilizer concentrations from 0 to 100 mug N g-1 soil showed positive response on ETS activity. However, at concentrations of 200 and 400 mug N g-1, the activity was reduced significantly. The pesticides and higher rates of fertilizer caused an improvement in the soil phenol contents and it increased with increasing concentration of agro-chemicals. The fertilizer and pesticide incorporation didn't produce any significant change in soil protein content while the response of biomass phospholipid content was nearly similar to ETS activity; it increased with lower rates of N-fertilizer but decreased at higher rates.
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