residual phytotoxic effect of some paddy herbicides on the growth of cress and lettuce

one of the crucial issues before the second cropping is having enough knowledge about the residue effect of first crop herbicides on second crops. this experiment was conducted to investigate the possible inhibitory effect of some selective paddy herbicides residues to second cropping. experimental factors were included common paddy herbicides (thiobencarb, butachlor, oxadiargyl, bensulfuronmethyl, and non- herbicide control) and test plants (lettuce (lactuca sativa l.) and cress (lepidium sativum l.)). at first, herbicides were applied in paddy field and bioassay was carried out by using the soils of plots treated with those herbicides and test plants. results showed that, in general, residual effect of paddy herbicides on the growth of second crops was different depending on plant type and herbicide. compared with aerial parts, roots of the plants tested were more sensitive to residual herbicides. butachlor showed the least (≤9%) and oxadiargyl the most (≥60%) inhibition on test plants, and bensulfuronmethyl and thiobencarb also had statistically similar inhibitory effect on the roots of the test plants. based on results of this study, the growth of lettuce and cress as second crops in paddy fields could be significantly reduced by the residue of some paddy herbicides including thiobencarb, oxadiargy and bensulfuronmethyl.