Factors affecting persistency and residual activity of herbicides in soil

点击翻译按钮获取中文摘要

The study was conducted to obtain the basic information on factors affecting the persistency and the residual phytotoxic activity of herbicide in soil for developing the rational weed management by herbicides. The results obtained in the study are summarized as follows.1.The amount of any herbicide applied to soil was detected much greater in solid phase than in soil water at the application and the amount in soil water decreased more remarkably than in soil solid with time after application. The amount of each herbicide in soil solid was different between soil types but the amount of adsorption on soil organic matter was similar. The results demonstrated that soil organic matter was a main factor dominating the adsorption of herbicide in soil. 2.The phytotoxic activity of each herbicide was correlated with the concentration in soil water but not with the amount in total soil, except for naproanilide which was hydrolyzed to be its active compound (NOP). In case of naproanide application to soil, the phytotoxicity depended on NOP concentration in soil water. The residual phytotoxic activity differed in the soil types but the degree of phytotoxic activity was coincided with the concentration in soil water. 3.The phytotoxic activity of cumyluron and thenylchlor on the growth of Eleocharis kuroguwai or barnyaydgrass seedlings was induced by absorption of this herbicide by the absorptive parts from the soil water in the herbicide treated layer formed in the top-soil, regardless of emerging depth.These results suggest that the concentration of herbicide or its active metabolite is dominating factor for the phytotoxic activity of herbicide in soil and that the concentration in soil water is determined by soil factors such as adsorption and degradation activity on herbicide behavior in a time dependent manner. In addition, emergence depth and the herbicide-absorption parts of target weeds is suggested to be a factor determining the phytotoxic activity in soil.