The role of Rhizobium in Nitrogen Management in Agricultural Lands under Legumes Cultivation

Rhizobia are one of the most important soil bacteria that have a symbiosis nitrogen fixation relation with legumes. The average amounts of fixed nitrogen in legumes are about 200-300 Kg N.ha-1. It is fixed annually 30-40 million tones of nitrogen by symbiosis systems. Legumes have important roles in feeding and protein needs of human and livestock. The largest areas under grain legumes cultivation in Iran belongs to Lorestan province. About 60 percent of grain legumes are produced in Fars, Lorestan, Khuzestan and Azerbayjan-Sharghi provinces. The largest areas under forage legumes cultivation in Iran belongs to Azerbayjan-Sharghi and Azerbayjan-Sharghi provinces. The researches revealed that rotation with legumes and using them as green fertilizers have significant effects on increasing of soil nitrogen. Low efficiency of native bacteria in nitrogen fixation, salinity, acidity, temperature and humidity, toxicity and deficiency of elements, are the most important limiting factors of nitrogen fixation. The best recommendations are evaluation of native symbiotic Rhizobia and necessity of inoculation and study of possibility of new legumes cultivation with high rating in fixation or with rotation of other crops. Utilization the guidelines presented in this paper along with education and extension of recent development for awareness of benefits and advantages of green manures and legumes cultivation is a hopefully approach.