Effects of Pesticides Use (Glyphosate & Paraquat) on Biological Nitrogen Fixation

Pesticide usage is becoming increas- ingly necessary to escalate agricultural productivity and meet food production needs. However, it harms in different degrees all living organisms, plants, and animals, whether terrestrial or aquatic. Soil micro- organisms, are microbes belonging to microorgan- isms, are the first to be specifically affected by pes- ticides. This study aims to evaluate the impact of two herbicides, paraquat and glyphosate, on symbiotic nitrogen-fixing bacteria. Our study was carried out in the greenhouse. Bituminaria bituminosa plants were inoculated with four different nitrogen-fixing bacteria, Pantoea agglomerans, Rhizobium nepotum, Rhizobium radiobacter, and Rhizobium tibeticum, and then treated with varying herbicide concentrations were selected according to the doses recommended by the National Office of Food Safety (ONSSA) and according to a survey conducted among farmers in the Meknes region-Morocco, (0.05, 0.1, 5.4, 10.8 g/L glyphosate and 0.05, 0.1, 2, 4 g/L paraquat). After 6 months after sowing, the following parameters were evaluated: nodule number, nodule mass, nodule weight, nodule dry, and fresh weight, nitrogen con- tent, and symbiotic efficiency. At higher doses (5.4, 10.8 g/L for glyphosate and 2, 4 g/L for paraquat), both herbicides decreased the number and the size of nodules, the weight of nodules, nitrogen content of Bituminaria bituminosa and symbiotic efficiency of the four different nitrogen-fixing bacteria studied. The effect of herbicides increased as the used concen- tration increased. The current research demonstrates that the decreased growth of herbicide-treated plants was caused by herbicides’ direct effects on rhizobia rather than herbicides’ indirect effects on Bituminaria bituminosa.