Biotoxic Effects of Herbicides on Growth, Nodulation, Nitrogenase Activity, and Seed Production in Chickpeas

Abstract

The effects of pre‐emergent (PRE) application of methabenzthiazuron (MBT), terbutryn, and linuron on plant vigor, number of nodules formed, nitrogenase activity (NA), chlorophyll contents, nitrogen (N) uptake, and seed yield were assessed in inoculated chickpeas, grown in sandy clay loam soil, in a controlled environment. The PRE application of MBT, terbutryn, and linuron at 2.5, 1.25 and 2 g a.i. kg−1, respectively, had no significant adverse effect on plant vitality, yield, and NA of excised nodules in inoculated chickpea plants, but reduced these parameters at 7.5, 3.75, and 6 g a.i. kg−1 of soil. Among the herbicides tested, linuron at each dose rates significantly (P≤0.05) decreased the grain yield, whereas terbutryn at 1.25 and 2.5 g a.i. kg−1 improved the grain yield by 19.4% and 11%, respectively, relative to the nonherbicide control. While comparing the sum of mean values of toxicity of all dose rates of each herbicide on grain yield, the toxicity increased in the following order: control=linuron>methabenzthiazuron>terbutryn. Nodulation (nodule number per plant and their dry mass) and chlorophyll contents per plant decreased consistently with increased herbicide rates, except linuron, which at 2 g a.i. kg−1 improved nodulation at both 45 and 90 days after seeding and corresponded with Mesorhizobium activity. The N content in grain and straw significantly decreased at the highest tested rates of each herbicide. Linuron at 2 and 4 g a.i. kg−1 improved N content in straw, whereas at 4 g a.i. kg−1 it significantly reduced N content in grain.