بررسی اثرات کودهای زیستی حاوی باکتریهای تثبیتکننده غیرهمزیست نیتروژن و حلکننده فسفات بر روی صفات کمی و کیفی گندم (Triticum aestivum)

Introduction Wheat crop plays an important role in food security in a country such as Iran. Therefore, serious attention has been paid to ecological farming systems and sustainable management of wheat. For this purpose extensive efforts is done to find proper strategies to improve the quality of soil, agricultural products and started removal pollutants. One of the factors to achieve sustainable agriculture is to use natural agents such as biofertilizers. Several mechanisms are proposed to explain how effective plant growth promoting rhizobacteria is for growth and development of plants. These mechanisms include two groups, direct and indirect in general. Indirect mechanism is to increase absorption and availability of the nutrient elements soluble, producing plant growth regulators, siderophore production of iron chelator, and the phosphate soluble. Through indirect mechanisms such as antagonistic relation, PGPRs moderate the harmful effects of of plant pathogens and thereby lead to increase plant growth. The main goal of this study was to investigate the effect of biofertilizers containing non-symbiotic nitrogen fixing and phosphate solubilizing bacteria on quantitative and qualitative traits of wheat. Materials and Methods This Experiment was conducted in the research farm of Baykola agricultural research stations affiliated by agriculture and natural resources research center of Mazandaran during 2011-12 cropping season. In order to determine physical and chemical properties of the soil samples were taken from the depth of 0-30 cm,. Experimental design was split plots arrangement based on randomized complete block design with three replications. In this experiment chemical fertilizer was assumed as the main plot in 3 levels include: 1- noconsumption (C0), 2- equivalent to 50% of the fertilizer recommendations (C1), 3- equivalent to 100% of the fertilizer recommendations(C2) and two types of biological fertilizers was applied in the sub plot in 4 levels: 1-noinoculation (B0), 2- Seeds inoculated with nitrogen fixing bacteria (B1), 3-Seed inoculation with phosphate solubilizing bacteria (B2), 4- Combined application of bio-fertilizers (B3). Results and Discussion Analysis of variance showed that grain yield, plant height, leaf area index, yield components, straw weight, biological yield, harvest index, percent of nitrogen and grain protein were influenced by different levels of biological and chemical fertilizers (Table 3). The highest grain yield was obtained using C2B3, combination treatments using chemical fertilizers and biofertilizers (PSB+NFB). The results of interactions between chemical fertilizers and biofertilizers showed the using 100% of the recommendations fertilizer along with biofertilizers (PSB+NFB) significantly increased grain yield (Table 5), compared with control. Due to increasing activity of bacteria Aztobacter chroococum, Azospirillium brasilense enhanced nitrogen fixation and released phyto hormones and thereby increased nutrient uptake by the roots. In addition, Pseudomonas Potida and Pantoea agglomerace had beneficial effects beside phosphorus uptake. These bacteria increased absorption and dissolved nutrients in the soil around the roots. PGPRs produced the plant growth regulator, organic acids and increased the ability to absorb elements such as iron, zinc and other micro elements and ultimately were effective in increasing crop yield and percent of nitrogen and grain protein. Conclusions Results of the experiment showed that using phosphate solubilizing bacteria and nitrogen fixing simultaneously or individually increased total plant biomass, grain nitrogen, protein content, yield components and crop yield. However, the combined use of phosphate solubilizing bacteria and nitrogen fixing compared to use of individually was more s effective. A synergic effect was found between chemical fertilizers and biological fertilizers. It is recommended to apply chemical fertilizers along with biological fertilizers to achieve highest possible yield.