Effect of bacterial inoculation on grain and soil nutrient elements of linseed (Linum usitatissimum L.) under different irrigation levels

Oil of linseed are used in various industries. linseed seeds contain bioactive components which reduce formation of cancerous colonies. Drought is one of the factors that reduces the crop production in most part of the world. These days several techniques are used in order to increasing plants tolerance to drought. One of these methods is seed pretreatment with plant growth promoting bacteria. These bacteria through mechanisms such as phosphate and potassium dissolution, nitrogen fixation, production of siderophore and growth regulators, production of hydrolytic enzymes and exopolysacharides increase tolerance and yield of crops under stressful conditions. Since water deficit is one of the main limiting factor of production in Iran and the use of chemical fertilizers caused much environmental pollution, so this study was conducted to investigate the effect of bio fertilizers as plant growth promoting bacteria on linseed under water deficit condition.

This study was carried out in split plot experiment based on randomized complete block design with three replications in 2015 at the research farm of Shahrekord university. Factors were irrigation in three levels (full irrigation, 75 and 50 percentage of full irrigation) and bacteria in seven levels (control, Bacillus sp strain1, Bacillus sp strain2, Bacillus amyloliquefaciens, Azotobacter Chroococcum, Pseudomonas putida and Azospirillium lipoferum). Applying of stress began from stem elongation. In ripening stage, grain yield and amount of P, Fe and Zn nutrients in grain were measured. After crop harvesting EC, pH, P, Fe and Zn of soil also were measured. Analysis of variance and correlation between traits used by SAS software, means comparison by LSD and interaction were carried out by slicing.

Interaction of irrigation and bacterial inoculation on grain yield, P percentage and concentrations of Fe and Zn in grain and soil EC were significant. Bacterial treatments in three irrigation levels showed the highest grain yield, P percentage in grain, concentrations of Fe and Zn in grain and soil EC while control treatments showed the lowest amount. Amount of nutrients in soil increased by increasing stress levels. Also, bacterial treatments had the lowest nutrients of soil in comparison with control treatment. Among bacterial treatments Bacillus sp strain1, Bacillus amyloliquefaciens and Azotobacter Chroococcum were more effective while Azospirillium lipoferum was not. Significant negative correlation between P percentage in grain and concentrations of Fe and Zn in grain with concentrations of P, Fe and Zn in soil was observed.

The use of plant growth promoting bacteria by increasing nutrients absorption from soil can increase grain yield. In fact, growth promoting bacteria by absorbing soil nutrients and contributing their absorption by plant may reduce the amount of soil nutrients.