Abstract: With plastic rhizobox system,this paper studied the degradation behavior of methamidophos in the rhizosphere and non-rhizosphere of phaiozem and burozem planted with soybean.The results suggested that methamidophos could be rapidly decomposed in soil environment despite its higher acute toxicity,and its residual amount in phaiozem was generally below the level in burozem under same condition.In the absence of soybean (control),the residual amount of methamidophos at the 2nd day of incubation was about 33% in burozem,whereas only about 26% in phaiozem.An accelerated degradation of methamidophos in soybean rhizospheric soil was observed, especially in phaiozem.At the 9th day of incubation,the insecticide residue in the middle rhizobox phaiozem and burozem with soybean was decreased by 87.5% and 76.0%,respectively,compared with that of the control.The degradation process of methamidophos in soil environment followed the first-order equation,and its half-life was about 2 days.

Key words: Brachionus calyciflorus, Sexual reproduction, Population growth, Resting egg prodution