Studying the effects of combined application of chemical and biological fertilizers of potassium on yield and yield components of wheat (Triticum aestivum L.) under soil moisture shortage

Introduction Water deficit in soil is a common phenomenon in plant cultivation and can have significant negative effects on their growth. Potassium is an element that increases the resistance of plants to dehydration, salinity stress. If the amount of potassium is reduced, the apertures will not function properly and will disrupt the photosynthesis process and the rate of growth of the crop.The use of biological fertilizers composed of bacteria and fungi can help to optimize the use of fertilizers. These fertilizers, by dissolving the mineral compounds of the soil, facilitate the absorption of the elements by the plants. Therefore, the present study was conducted to investigate the effect of the combined use of potassium chemical and biological fertilizers in order to modify the effects of soil moisture deficiency on yield and yield components of wheat. Materials and methods In order to modify the effects of soil moisture shortage on yield and yield components of wheat, an experiment was carried out based on factorial with completely randomized block design with three replications during 2015-2016 in Ahvaz region. The first factor was irrigation regimes on basis of evaporation from evaporation pan at three levels include: 60 mm (common area), 90 mm and 120 mm. The second factor including combination of chemical and biological of potassium include, 1-completely through potassium sulfate fertilizer (without bio-fertilizer) (control), 2-75% potassium sulfate+Potabarvr2, 3-50% potassium sulfate+Potabarvr2 and 4-25% potassium sulfate+ Potabarvr2.The application of irrigation treatments started at the beginning of the tillering and continued the final harvest. To fertilize the seeds with bio-fertilizer Potabarvar 2, the seeds were first wet, then spread on plastic surfaces, and with Pb-2 biofertilizer, 100 grams per hectare per hectare were seeded on the basis of the manufacturer's recommendation. Potassium fertilizer was used as the basis for the treatment of 100 kg of pure potash per hectare from the source of potassium sulfate as a base and before planting. Results The results showed that the effect of irrigation was significantly different on ear number per square meter, grain number per spike, 1000-grain weight, grain yield, biological yield and harvest index. The effect of combined application of fertilizer on all traits was significant except harvest index. The maximum number of spikes per square meter, grain number per spike, 1000 grain weight, and harvest index belonged to irrigation based on 60 mm evaporation pan and the lowest was 120 mm evaporation pan. Also, the maximum number of spikes per square meter, number of seeds per spike, 1000 grain weight and harvest index were 75% potassium sulfate + Potabarvr2.In regard to grain yield , the maximum was obtained under 60 mm evaporation and 75% potassium sulfate + Potabarvr2 by 5970 kg/ha. The minimum grain yield was under 120 mm evaporation and 25% potassium sulfate + Potabarvr2 by 2994 kg/ha. Conclusion The overall results of this study showed that: 1- With increasing moisture stress, traits such as grain yield, yield components, harvest index and biological yield decreased. Reduction in grain yield was higher than biological yield, indicating greater sensitivity of reproductive organs to vegetative organs under moisture stress conditions. 2. With the application of potassium sulfate, conditions can be established for plant establishment and ultimately increased yield. The best yield and yield traits were observed in 75% potassium sulfate + Potabarvr2. The use of bacteria seems to have affected the plant by increasing the potassium bioavailability or by producing growth regulating hormones. On the other hand, due to the fact that in all three irrigation regimes, grain yield increased by 75% potassium + Potabarvr2 sulfate in comparison with non-use of biological fertilizers (control) (all through potassium sulfate). Therefore, this fertilizer combination can be recommended in the moisture stress and without stress conditions in the region.