Study of inoculation of soybean with different strains of Bradyrhizobium Japonicum on nodulation and nitrogen fixation

To study the effect of inoculation of soybean cultivars with different strains of Bradyrhizobium japonicum for determining the best bacteria-cultivar combination, an expriment was conducted using split plot design with 3 replications in 2001 cropping season at seed and plent Improvement Institute, Karaj, Iran. The other experiment was carried out using randomized complete block design in the green house. The factors student were two cultivars of soybean (Williams and Line L11) and four bacterial strains of Bradyrhizobium japonicum including Helinitro, Highstick, Soyar and SWRI and a control plot (without bacteria). Characteristics such as number and weight of nodules per plant, weight of plant dry matter at harvest stage and shoot/root per plant and percentage of nitrogen in the soil as well as the amounts of nitrogen in plant shoot: with N-difference method were measured and recorded. The results showed that Highstick could fix more nitrogen than other strains. In the other hand, cultivar L11 had better symbiotic activity than cultivar Williams and fixed higher amount of nitrogen. Highstick and L11, in most characters, found to be the best combination.