Biotoxic effects of the herbicides on growth, seed yield, and grain protein of greengram

We studied the effects of atrazine, isoproturon, metribuzin and sulfosulfuron on plant vigour, nodulation, chlorophyll content, seed yield and protein content in seeds, in greengram inoculated with Bradyrhizobium sp. (vigna). The pre-emergence application of the four herbicides at 400 μg kg^-1 of soil adversely affected the measured parameters. The average maximum increase of 10 % in seed yield occurred at 200 μg kg^-1 of sulfosulfuron, while atrazine at 200 and 400 μg kg^-1 of soil decreased the seed yield by 25 % and 40%, respectively. The average maximum chlorophyll content of 1.2 mg g^-1 was obtained at 200 μg kg^-1 of sulfosulfuron which declined consistently for all herbicides and increasing dose rates. Sulfosulfuron at 200 μg kg^-1 increased the number of nodules found per plant by 7 % at 45 days after seeding the greengram. In contrast, the tested dose rates of atrazine, isoproturon and metribuzin significantly reduced the nodulation (nodule number and dry mass). The average maximum grain protein of 182 mg g^-1 was obtained for sulfosulfuron at 400 μg kg^-1, while minimum grain protein was obtained at 400 μg kg^-1^- of isoproturon (124 mg g^-1) and atrazine (125 mg g^-1) application. Among the herbicides tested, atrazine and metribuzin showed a large degree of phytotoxicity to the crop, inhibiting its vegetative growth and was thus incompatible with greengram.