Effect of Trichoderma on growth and nutrition of pistachio trees under common garden condition

physicochemical properties and plant growth is to use biological fertilizers such as plant growth-promoting fungi. Biological fertilizers could be used as a supplement or alternative to the chemical fertilizers in sustainable agriculture. Accordingly, to investigate the effect of Trichoderma fungi on the nutrition and growth of pistachio trees, an experiment was conducted in a randomized complete block design, in which each block contains four treatments, control (T0) (no inoculation), Trichoderma harzianum (T1), Trichoderma viride (T2) and treatment of an equal mixture of T1 and T2 (T3) in three replications under common garden conditions. The results showed that all three fungal treatments significantly increased growth parameters including branch length (up to 60%), the number of vegetative buds (up to 30%), leaf area (up to 50%), and chlorophyll index (up to 171%) in pistachio trees in comparison with control. The use of fungal treatments significantly increased the concentration of potassium and zinc in pistachio leaves up to 20 and 70%, respectively, compared to the control. T2 treatment significantly increased the phosphorus concentration by 14% and the calcium by 40% in pistachio leaves. The application of  T1 and T3 treatments significantly increased the magnesium concentration up to 25%, in pistachio leaves compared to the control. T1 treatment significantly increased the leaf iron concentration by 28% compared to the control. The application of T1, T2, and T3 treatments significantly increased the content of total chlorophyll up to 73.2, 171, and 59.2% of and carotenoids up to 77.6, 3.80, and 64.8% in pistachio leaves respectively, compared to the control. According to the results of this study and after further field experiments, it can be expected that the studied fungi can be used as biofertilizers (alone or in combination) to reduce the utilization of chemical fertilizers in the future.