Effect of simultaneous application of Sinorhizobium and phosphorus on the growth, nitrogen fixation and some nutrients uptake in Fenugreek (Trigonella foenum- graecum L.)

Background and Objectives: Nitrogen is one of the most important nutrients in plants which its shortage in soil is the main factor limiting plant growth. Molecular nitrogen comprises about 80 % of the atmospheric gases whereas it is not directly absorbable in plants. Biological nitrogen fixation (BNF) through symbiosis with leguminous plants is one of the most important ways entrance of inorganic nitrogen into soils. Inoculation of legumes with rhizobia is also an important process to maximize biological N2 fixation capacity in these crops. Moreover, phosphorus is an essential element to convert atmospheric N (N2) into ammonium (NH4) in nitrogen fixation process. Hence in this study, the effects of simultaneous application of Sinorhizobium and phosphorus on the growth, nitrogen fixation and nutrients uptake of Fenugreek were evaluated.
Material and method: To evaluate the effect of combined application of Sinorhizobium and phosphorus levels on growth, nitrogen content and other nutrients uptake of Fenugreek, five isolates of Sinorhizobium were selected from bacterial bank of soil science department, University of Rafsanjan and used in a greenhouse experiment. These bacteria were had isolated from Fenugreek root nodules and had the highest symbiotic effectiveness. The greenhouse experiment was conducted in factorial based on completely randomized design with three replications including two factors i) five levels of bacteria (inoculation with four Sinorhizobium isolates (SR4,SR5,SR12, SR16) and non-inoculated as control) ii) four levels of phosphorous (0, 20, 40 and 60 mg kg-1soil).
Results: Results showed that simultaneous application of Sinorhizobium and phosphorus levels significantly increased the number of nodule and shoot dry weight. Also combined application of Sinorhizobium and phosphorus levels significantly enhanced amounts of nitrogen, phosphorus, iron and magnesium in shoot of Fenugreek. Interaction of the isolates and phosphorus levels didn’t have any significant effect (p<0.05) on root dry weigh and uptake of zinc and couple, while Root dry weigh and amounts of zinc and couple in the Fenugreek were significantly increased by application of Sinorhizobium isolates and phosphorus levels each one alone.
Conclusion: this study revealed that simultaneous application of isolate SR4 and 60 mg phosphorus per kg soil was the most efficient treatment in improvement of growth, nitrogen content and other nutrients uptake of Fenugreek. In comparison with control, this treatment enhanced soot dry weight from 0.25 to 2.25 g pot-1, nodule number from 70 to 570, nitrogen and phosphorus contents from 6.95 and 0.28 to 100 and 2.54 mg pot-1 and also iron and manganese uptake from 0.02 and 0.03 to 0.19 and 0.28 µg pot-1respectively.