Effect of inoculation of Rhizobium leguminosarum in combination with different levels of Peseudomonas fluorescens on some quantity traits of Vicia faba

Application of bacteria as bio-fertilizers is one of the key issues for sustainable agriculture development whose most important result is the reduction of environmental pollution by reducing the need for chemical fertilizers. Faba bean is cultivated for two important reasons: nutritional value of grains, ecological value for nitrogen fixation and application in cereal alternations. The present study aims to investigate different rates of Pseudomonas fluorescens in combination with and without Rhizobium leguminosarum on some growth factors and yield Characteristics of Vicia faba.

Farm experiments over the years 2015-2016 and 2016-2017, was conducted in complete randomized block scheme in the form of split plots. Rhizobium leguminosarum was considered as the main plot and Peseudomonas fluorescens bacteria were applied in five levels (0, 9×103, 9×105, 9×107, 9×109) as sub-plots. The plant height at the time of physiological maturity, leaf area index (LAI) at pod time, number of seeds and pods per square meter in a sample of 10 plants and the weight of 100 seeds were measured. Grain yield with 11% moisture content in the first year and 9% in second year, green pod yield and biological yield in per unit area were obtained. Also harvest index was measured from the ratio of economic yield to biological yield.

Results for two years showed that the effectiveness of bacteria is influenced by climatic conditions. In the first year, number of seeds and pods per square meter were affected by the interaction of Rhizobium and Pseudomonas. Application of inoculant with Rhizobium and a total of 9×105 Peseudomonas fluorescens bacteria per ml was the best choice. In addition, Peseudomonas fluorescens (9×105) increased significantly (p˂ 0.05) the green pod yield in comparison with the control. . Inoculation rate of 9×105 Pseudomonas/ml resulted in 14% greater green pod yield for Faba bean in comparison with the non-inoculation case. Decrements in mentioned yield were observed when the number of Pseudomonas increased from 9×105 up to 9×107. By increasing the number of (9×109), green pod yield increased again, whit no significant difference with rate of 9×105 Peseudomonas/ml. In the first year, application of inoculant with Rhizobium resulted in 10% greater seed yield for Faba bean in comparison with the non-inoculation. In the second year, the effectiveness of Rhizobium was reduced and the greatest effect was related to application of inoculum with the number of 9×105 Peseudomonas bacteria, with no significant difference with the higher populations of this bactria.

This study revealed that the overall effect of Pseudomonas fluorescens on the yield and its components has more stability than Rhizobium in different environmental conditions. The best population of Pseudomonas fluorescens for inoculation of Vicia faba seeds was determined 9×105 living bacteria per ml of inoculant that seems it is the response threshold for Vicia faba.