The use of antagonistic microbes and potassium fertilizer on potato cultivation at the medium land was carried out to improve plant endurance, yield and quality. Application of potassium doses and suitable antagonistic microbial types will strengthen plant cell walls and plant nutrients to be fulfilled. This research aims to study the growth response, yield and quality of potato bulb in land medium with the application of antagonistic microbes and potassium fertilizer. The height of the land is around 670 meters above sea level, the texture of the clay and the experimental design used is the Split Plot Design. Three kinds of antagonistic microbes are A1 (Pseudomonas fluorescens), A2 (Streptomyces sp. + P. fluorescens), A3 (Trichodermaviride + Streptomyces sp. + P. fluorescens), and three types of Potassium doses are: D1= 125 kg Ha-1 KCl, D2 = 250 kg Ha-1 KCl, D3 = 375 kg Ha-1 KCl. Each treatment has three replications, the number of plants per experiment plot is 22 plants, and the sample plants used in each trial plot are 6 plants. The results showed that the administration of P.fluorescens + Streptomyces sp. + T. viride and 250 kg Ha-1 KCl and 375kg Ha-1 KCl doses tend to produce growth, tuber fresh weight per hectare, tuber dry weight percentage, tuber specific gravity and higher sugar content than other treatments.