Interaction of Rhizobium inoculation and nitrogen levels on some morphophysiological and yield characteristics of soybean (Glycine max L.) varieties in Kermanshah climate conditions

The soybean plant [(Glycine max (L.) Merr.] has the ability to air nitrogen fixation through the bacteria of the Rhizobium japonicum. Nitrogen fixation, although not providing the plant's needs for maximum yield, but in the right conditions, it may be up to about 80% of the total nitrogen required for the plant to stabilize.Use of the nitrogenfixation mechanism of nitrogen will reduce production costs, mitigating environmental pollution and maintain soil construction. In soybean, amount of nitrogen fixation depend on the usage and condition of inoculation, the type of soil, the reaction of the variety and the weather conditions of the region.With attention to importance of soybean, this study fulfilled with the aim of evaluation the effect of inoculation of Rhizobium and different levels of nitrogen on some morphophysiological characteristics and yield of soybean cultivars. This experiment was conducted as split-split plot based on a randomized complete block design with three replications at the Research Farm of Campus of Agricultural and Natural Resources, Razi University, Kermanshah during2009.The main factor was nitrogen fertilizer (0, 50, 100, 150 and 200 kg ha-1) from urea source, sub-factor of soybean varieties (Williamz and Hobbit) and sub-sub-plot of inoculation of Rhizobium japonicum (no-inoculation and inoculation).In this experimenttraits were investigated such as leaf area index, plant height, quantum yield, photosynthesis efficiency index, canopy temperature, stomatal conductance and chlorophyll index atearly-flowering stage and biomass, grain yield, harvest index, number of pods per plant, number of seeds per Pods, 1000-seed weight, number of branches per plant and seed oil percent. The results showed that in the early-flowering stage by increasing nitrogen levels leaf area index versus stomata conductance were enhanced, but the highest efficiency of photosynthesis was obtained at 50 and 100 kg ha-1 nitrogen.The highest quantum yield was obtained for inoculation conditions and consumption of 100 kg ha-1for Williamz variety.Plant height for Hobbit variety increased compared to Williams by more than 100 kg ha-1 nitrogen. In the ripening stage, the effect of nitrogen fertilizer, soybean cultivars and seed inoculation were significant on biomass yield, seed yield, harvest index and 1000-seed weight.The response of biomass was different in two varieties from nitrogen and inoculation. The highest amount was for Williamz(50 kg ha-1) and Hobbit(150 and 200 kg ha-1). Rhizobium inoculation increased seed yield by 570 kg ha-1.The highest grain yield was obtained amount of 5400 kg ha-1 with 50 kg ha-1 nitrogen fertilizer and inoculation at Williamz variety. In Kermanshah climatic conditions, Williams and Hobbit varieties produced maximum seed yield by 50 and 100 kg ha-1 nitrogen with Rhizobium inoculation. Williamz had the highest yield to Hobbit.