Evaluation Effect of Inoculum Prepared from Local Bacterial Isolates of Rhizobium and Nitrogen Fertilization on some Growth Traits of Mung Bean Plant in Gypsiferous Soil

Abstract

The root nodule bacteria are utilized in the production of natural biological fertilizers to achieve clean agriculture by reducing chemical fertilizers. Therefore, the bacterial inoculum was prepared from local isolates of Rhizobium leguminosarum and Bradyrhizobium japonicum, which were morphologically and molecularly characterized. Subsequently, the efficacy of the prepared inoculum was tested in the formation of root nodules and some growth traits of mung bean plants in gypsiferous soil at three levels of nitrogen fertilization (0, 40, 80) kg N ha-1 The results showed a significant increase in all plant growth traits during the flowering stage for the treatments inoculated with Rhizobium leguminosarum and Bradyrhizobium japonicum bacteria in comparison to the treatment without inoculation. The inoculated treatments outperformed the non-inoculated treatment significantly. Additionally, the treatment inoculated with Bradyrhizobium japonicum showed a significant superiority over the treatment inoculated with Rhizobium leguminosarum in all studied growth traits, the recorded values for the count of root nodules were (0.00, 8.33, 35.11) nodule. plant-1, The wet mass of nodules was (0.00, 0.091, 1.802) g. plant-1, and dry mass of nodules was (0.00, 0.010, 0.337) g. plant-1. The plant height was (52.11, 56.22, 58.05) cm. plant-1. The dry mass of the vegetative part, was (14.03, 20.10, 23.05) g. plant-1, and, the dry mass of the root part was (1.37, 2.57, 2.67) g. plant-1. The nitrogen content was (1.547, 2.765, 3.028) % phosphorus (0.121, 0.236, 0.377) %, and potassium (1.168, 2.342, 3.562) % in the vegetative part. The absorbed nitrogen in the vegetative part was (217.41, 541.10,718.02) mg. plant-1. These values were recorded for the non-inoculated treatment, Rhizobium leguminosarum inoculated treatment, and Bradyrhizobium japonicum inoculated treatment, respectively. The results showed a significant superiority for the 40 kg N ha-1 fertilized treatment in comparison to both the unfertilized treatment and the 80 kg N/ha-1 fertilized treatment in all studied traits. The interaction effect was significant, as the treatment that was inoculated with Bradyrhizobium japonicum and 40 kg N ha-1 fertilized treatment exhibited significant superiority over the other treatments in all studied traits.