This experiment was carried out during the spring growing season 2021 in the research field of the College of Agriculture and Forestry/Mosul University/Tourist Forest Area, to study the response of three factors in the characteristics of the quantitative yield of the two potato cultivars. The first factor included two cultivars of potatoes (Taurus and Universa), the second factor included bio-fertilizer (Trichoderma fungus) at two levels and for one time only (5 g.m2, without addition), and the third factor included potassium fertilizer as potassium sulfate at four levels (0, 100, 200, (300 kg. ha-1 ). The results were as follows: The treatment of the cultivar Universa gave the highest significant values in the number of total tubers, the average marketing weight of the tuber, the yield of one plant and the total yield of tubers, with a value of 15.63 tubers.plant-1 , 87.19 g.tuber-1 and 965.08 g.Plant-1 and 43.972 ton. ha-1 , respectively. The bio-fertilization treatment at a concentration of 5 g. m2 gave the highest significant values in the total number of tubers, the yield of one plant and the total yield of tubers with a value of 15.29 tubers.plant-1 , 900.92 g. plant-1 , 40,819 ton. ha-1 , respectively, and potassium fertilization treatment (300 kg. ha-1 ) gave the highest significant values in the average weight of the tuber and the average weight of the marketing tuber with a value of 65.30 g.plant-1

Trichoderma, biofertilizer, potassium sulfate, potatoes.