Effects of herbicides on biological nitrogen fixation in grain and forage legumes – A review

Legumes are an integral part of the farming systems. They are grown sole as well as inter/mixed crops. They not only provide food for human beings and fodder for animals but also fix atmospheric nitrogen in the soil. Nitrogen so fixed by various legwnes in association with diffe~ent species of rhizobia results in increased soil fertility. Everyone is interested in higher amounts of nitrogen fixation by legwnes but some factors limit their efficiency. One of these factors could be the herbicides. Though herbicides are applied for controllng weeds yet indirectly some of them may influence their (legwnes') nitrogen-fixing activity. Herbicidal effect on nitrogen fixation may be either beneficial or deleterious. In this paper an attempt has been made to review the literature on the effects of herbicides on biological nitrogen fixation in some of the commonly grown legwnes, either for food or forage.