effects of soil residues of some wheat sulfonylurea and aryloxy phenoxy propionate herbicides on chickpea (cicer arietinum l.) growth, nodulation and biological nitrogen fixation

introduction soil herbicides residue in agroecosystems is one of the important problems due to herbicides application. however herbicides residue in soil extend the period of weed control. nevertheless, it may persist longer than desired and injure subsequent crops in rotation. herbicides vary in their potential to persist in the soil. some herbicides such as sulfonylurea herbicides are very persistent. among registered herbicides for weed control in wheat fields in iran, sulfonylurea (e.g. sulfosulfuron and metsulforon-methyl+sulfosulforon) and aryloxy phenoxy propionate (e.g. diclofop-methyl, fenoxaprop-p-ethyl) are more important groups. with regard to the persistence of mentioned herbicides in soil, sulfonylurea herbicides may create problems in crop rotation. since chickpea (cicer arietinum l.) is one of important crops in rotation with wheat in iran and the effect of sulfosulfuron, metsulforon-methyl+sulfosulforon, diclofop-methyl and fenoxaprop-p-ethyl on its growth, nodulation, and nitrogen fixation have not been studied yet. this study was conducted to investigate the effects of mentioned herbicides residue in soilon growth, nodulation, and nitrogen fixation of chickpea genotypes in controlled conditions. material and methods in order to study the effects of soil residue of some sulfonylurea and aryloxy phenoxy propionate herbicides on growth, nodulation and nitrogen fixation of chickpea (cicer arietinum l.), a pot experiment was conducted using factorial arrangement in a completely randomized design with three replications. factors included herbicide type in four levels (diclofop-methyl, fenoxaprop-p-ethyl, sulfosulfuron and metsulforon-methyl+sulfosulforon), herbicides residue in soil in eight levels (0, 2.5, 5, 10, 15, 20, 30, and 40 percent of recommended dose for each herbicide) and chickpea genotypes in three levels (hashem, ilc 482, and kaka). after mixing the herbicide solution with prepared soil and planting, plants were maintained until the beginning of reproductive stage. in the early stage of reproductive, shoot biomass and root biomass, number of root node and total nitrogen content of plants were measured. the data were statistically analyzed using variance analysis, and differences among mean values of treatments were compared by duncan test (p≤0.05) in sas. for determination the dose of herbicides required to reduce 50% of plants response (ed50), the dose response curves were fitted simultaneously using the following three-parameter logistic model. f(x,(b,d,e))= d/(1+exp⁡〖{b(log⁡(x)-log⁡〖(e))}〗 〗 ) where f is the response (above ground dry weight, root dry weight and node dry weight), d is the upper limit, b is the curve slope, e denotes the dose required to give a response halfway between the upper and lower limits (ed50); and x is the herbicide concentration in soil. the validity of the above model and the comparison between the parameters were made using f-test for lack-of-fit with a 5% level of significance. results and discussion results showed that sulfonylurea (sulfosulfuron and metsulforon-methyl+sulfosulforon) and aryloxy phenoxy propionate (diclofop-methyl, fenoxaprop-p-ethyl) had the highest and the lowest effect on mentioned traits of plants, respectively. by increasing of sulfonylurea herbicides residue in soil, all measured traits decreased significantly (p≤0.01). however, soil residue of aryloxy phenoxy propionates herbicides did not significantly affect on chickpea genotypes. the lowest ed50 (0.0025 mg kg-1 soil) and the highest ed50 (0.0047 mg kg-1 soil) of sulfosulfuron herbicide soil residue for shoot biomass, were observed in hashem and ilc482 genotypes, respectively and the lowest ed50 (0.0057 mg kg-1 soil) and the highest ed50 (0.0837 mg kg-1 soil) of metsulforon-methyl+sulfosulforon herbicide soil residue, were observed in ilc482 and kaka genotypes, respectively. considering the results of the study, it can be noted that hashem genotype showed more sensitivity to sulfosulfuron and metsulforon-methyl+sulfosulforon herbicides soil residue compared to the other genotypes. generally, results of this experiment showed that soil residue of sulfosulfuron and metsulforon-methyl+sulfosulforon herbicides had significant and negative impact on chickpea growth. on the other hand, chickpea genotypes had different sensitivity to soil residue herbicides. conclusion results indicated that it is necessary to look the interval time in chickpea planting in rotation of wheat-chickpea. moreover, selection of less sensitive chickpea genotypes to soil residue of sulfosulfuron and metsulforon-methyl+sulfosulforon herbicides could be useful in their residue management.