effect of herbicides residue used in rice fields on growth characteristics of second crop in rotation in mazandaran province

abstract in order to evaluate the effects of rice conventional herbicides on rotational second crops (lettuce, cress, clover, canola and radish), soil microbial biomass and diversity, a field and glasshouse experiments were conducted in mazandaran province and research glasshouse of ferdowsi university of mashhad, respectively. five experiments were carried out for 5 second crop separately with treatment of different herbicide residue (1-butachlor 5 l/ha, 2-thiobencarb 5 l/ha, 3-oxadirgyl 3l/ha, 4-sunrice 3 l/ha, 5-setoff 150 g/ha and 6-check without herbicide) by using randomized complete block design. stem and root length, stem, root and total weight (root + stem) in two harvests (20 and 40 days after planting) were measured and anova was performed. in the first harvest mean comparison showed that canola, lettuce and radish were not affected at 95% confidence level by herbicide residue in any measured variables. clover stem length and weight were not affected by residue of any herbicides, however clover root length was affected by butachlor residue and was 28٪ lower than control. butachlor residues also led to root and total weight reduction in clover. butaclor residues also affected cress stem and total weight. in the second harvest canola, clover and radish in all variables were not significantly affected by any herbicide residues. sunrice residues reduced stem length significantly in lettuce. lettuce stem and root length and cress in stem and total weight were affected by oxadiargyl residue.