The effect of chemical and biofertilizer on the nutrient concentration of root, shoot and seed of bean (Phaseolus vulgaris L.) under drought stress

Legumes are the second most important food source in the world after cereals. Beans are very effective in stabilizing nitrogen and fertility of agricultural soil due to their coexistence with bacteria, and large amounts of nitrogen are added to the soil every year after harvesting this plant. Environmental factors, especially drought stress conditions, play a major role in the quantitative and qualitative characteristics of crops. Reduction of available water, especially at the beginning of the flowering stage and the occurrence of drought stress in legumes, while reducing the rate of vegetative growth and shortening the stage of reproductive growth has a negative effect on grain quality. Nutritional deficiencies in plants cause them to be sensitive to environmental stresses. Excessive use of chemical fertilizers in agriculture to provide the phosphate needed by plants has always caused adverse environmental effects and has led to a decline in the quality of agricultural products. However, the use of biofertilizers has many benefits over chemical fertilizers. Therefore, considering the importance of the above, the purpose of this study is to investigate the role of biofertilizer and phosphorus fertilizer on bean plant elements in drought stress conditions. An experimental split-split plot with three replications was performed to investigate the effect of bio-fertilizer and phosphate fertilizer application on nutrient uptake in roots, stems, and seeds of beans under drought stress in season 2016-2017 in Ilam city. Treatments included three levels of irrigation interruption (non-stress conditions, cut off in flowering stage, and cut off in pod formation stage) in the main plot and three levels of phosphate fertilizer (25, 50, and 100 kg. ha1) and application and non-application of biofertilizer. Drought stress treatment in this experiment was performed by stopping irrigation in two stages of full flowering and podding. All phosphorus fertilizer related to each treatment was applied to the ground at once during cultivation. After germination and establishment of the plants in the 2-4 leaf stage, the plants were thinned and one plant was kept in each pile. Weed control was done manually in two stages before flowering. The results showed that the highest nitrogen concentrations in roots, stems, and seeds under non-stress conditions (full irrigation) were 1.12, 1.77, and 3.19%, respectively. Also, the lowest nitrogen concentrations of roots, stems, and seeds in the cut-off flowering stage were 0.92, 1.46, and 2.63%, respectively. The mean comparison results showed that the highest grain nitrogen concentration in non-stress conditions (full irrigation) was 3.19%, which increased by 21.29% compared to the cut-off irrigation treatment at the flowering stage. The results showed that the highest concentration of root potassium in the conditions of irrigation interruption in the flowering stage and biofertilizer application was 2.63% and the lowest was obtained in the treatment without stress and non-application of biofertilizer (2%). The average comparison results showed that the highest concentration of potassium in the stem was obtained in the condition of cut off irrigation in the flowering stage at the rate of 4.35% and the lowest amount was obtained in the full irrigation at the rate of 3.60%. The results showed that in the treatment of biofertilizer application, the highest concentration of phosphorus in the grain was 0.265 percent, while the lowest in the treatment of non-application of biofertilizer was 0.226 percent.The application of phosphate fertilizer significantly increased the absorption of elements. The application of biofertilizer also significantly increased the concentration of nitrogen, potassium, and phosphorus in bean plants. In general, the results of this study showed that the use of biofertilizer and phosphate fertilizer could reduce the adverse effects of drought stress on bean plants and increase the absorption of elements in bean organs.