BACKGROUND: Available water and nutrient management are two important factors that affect yield and quality of wheat production. OBJECTIVES: Current research was done to assess the effect of chemical and biological potassium fertilizers on growth indices of bread wheat under water stress conditions. METHODS: This study was done via factorial experiment based on completely randomized block design with three replications during the agricultural year 2015-2016 in Ahvaz region (southwest of Iran). The first factor included irrigation regimes based on the evaporation pan method at 60 (local standard), 90, and 120 mm, and the second factor consisted of the combined use of chemical and biological potassium fertilizers at four levels: 1- 100% chemical fertilizer (potassium sulfate without the use of biological fertilizer) as control, 2- 75% potassium sulfate + Potabarvar2, 3- 50% potassium sulfate + Potabarvar2, and 4- 25% potassium sulfate + Potabarvar2. RESULT: The results indicated that irrigation after 60 mm of evaporation increased leaf area index, dry matter accumulation, crop growth rate, and net photosynthesis rate, resulting in enhanced yield. The highest grain yield, with an average of 5970 kg.ha-1, was obtained from the irrigation treatment based on 60 mm of evaporation with the consumption of 75% potassium sulfate + Potabarvar2. The lowest grain yield was observed in the treatment with irrigation after 120 mm of evaporation and the use of 25% potassium sulfate + Potabarvar2, with an average of 2994 kg.ha-1. CONCLUSION: In general, the study demonstrated that the application of bacteria along with chemical fertilizer influenced plant growth. Moreover, considering the significant increase in grain yield under the conditions of 75% potassium sulfate + Potabarvar2 in all three irrigation regimes compared to the control (no use of biological fertilizers), this fertilizer combination can be recommended under both moisture stress and non-stress conditions in the region. پرونده مقاله