Document Type : Research Paper - Legume
Author
Department Plant Production and Genetics, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran
Abstract
Introduction
Guar can form a symbiotic relationship with some strains of bradyrhizobium bacteria but in a weak way. Therefore, achieving a stronger symbiosis in the guar is important. Previous studies in some legumes, which do not include guar, show that the legume-bacterium symbiosis can be improved by applying silicates in the soil due to the uptake of silicon, which results in an improved yield. Since the production of silicates is expensive in the industry, recently, some studies focused on the ability of silicate-dissolving bacteria to dissolve silicates present or applied in the soil. Previous studies in some crops show that the soil inoculated with silicate-dissolving bacteria dissolves silicates present and used in the soil, resulting in an improved yield due to the better uptake of silicon and even other nutrients. The present study aimed to investigate the affectability of guar-bacterium symbiosis from soil application of various silicates (Na2SiO3, K2SiO3, Ca2SiO3, and Mg2SiO3) and soil inoculation with silicate-dissolving bacteria.
Materials and Methods
A pot experiment was performed on the campus of Bu-Ali Sina University in 2022 as a two-factor factorial (2×5) based on a completely randomized design with 10 replications. The first factor included the silicate type in five levels: control, Na2SiO3, K2SiO3, Ca2SiO3, and Mg2SiO3. Silicates were used at 100 mg/kg of soil. The second factor included soil inoculation with a commercial silicate-dissolving bacteria in two levels: 0 and 10 ml/kg of soil. Sixty days after planting, plants of half replications were harvested to measure shoot and root dry weight, nodule number and dry weight, shoot and root nitrogen content, and shoot silicon content. When 80% of the pods turned brown, plants of the other half replications were harvested to measure 100-seed weight, seed yield per plant, and seed gum content.
Results and Discussion
Based on our observations, guar seedlings grew faster in the pots treated with silicates. Except for seed gum content, other traits were affected by simple and interaction effects between factors. When silicates were not used, the root dry weight and 100-seed weight of guar were not affected by silicate-dissolving bacteria. While it increased the nodule number (34%), nodule dry weight (75%), shoot dry weight (42%), silicon content (16%), shoot nitrogen content (15%), root nitrogen content (41%), and seed yield per plant (25%). When the soil was not inoculated with silicate-dissolving bacteria, the application of all silicates significantly and equally increased silicon content in the guar’s shoot. Also, the co-combined application of silicates and silicate-dissolving bacteria resulted in greater silicon content in guar’s shoot. The highest silicon content (550.1 mg/kg of dry weight) was observed with K2SiO3 + silicate-dissolving bacteria.
Conclusion
The existence of a synergistic effect of the use of silicates and their dissolving bacteria on the investigated traits of guar was observed, which can cause more effective use of silicates in farms. Although the application of silicates and their dissolving bacteria did not affect the seed gum content, the result of increasing the seed yield per plant is the increase in gum production per plant.
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