Effect of Fertilizers on Nitrogen Fixing Bacteria from Root Nodules of Pea Plant

Background: Nitrogen-fixing bacteria such as Rhizobium spp. are vital for enhancing soil fertility and promoting plant growth. These bacteria inhabit the root nodules of legumes like pea (Pisum sativum) and contribute to sustainable agricultural practices. However, the application of fertilizers may interfere with their beneficial effects. Objectives: This study investigates the effects of organic and inorganic fertilizers on nitrogen-fixing Rhizobium spp. isolated from pea plant root nodules and evaluates their role in promoting plant growth through indole acetic acid (IAA) production. Methods: Bacteria were isolated from root nodules of pea plants and identified based on colony morphology and biochemical tests. Their sensitivity to NaCl, pH, tetracycline, and chloramphenicol was assessed. Pea plants inoculated with Rhizobium were monitored for stem length over a period of 4 - 7 days under various fertilizer treatments. The production of IAA by the bacterial isolates was quantified. Results: The isolated Rhizobium spp. exhibited small, translucent, mucoid colonies and were sensitive to NaCl, pH variations, tetracycline, and chloramphenicol. Inoculated pea plants demonstrated increased stem length compared to non-inoculated controls; however, the use of fertilizers reduced this growth-promoting effect. The isolates produced 4.10 g/mL of IAA, highlighting their potential role in plant growth enhancement. Conclusion: Nitrogen-fixing Rhizobium spp. significantly promotes plant growth through IAA production. However, the application of organic and inorganic fertilizers may inhibit these effects, suggesting that careful management of fertilizers is necessary for optimizing the benefits of biofertilizers in sustainable agriculture.