The research objective was to determine the influence of a long-term storage period for potato tubers, as well as variety and fraction and the fertilization applied upon the force value and deformation (tuber bending) when exceeding the biological resistance. The research was done upon the varieties (Baszta, Irga, Salto) at the surface application of mineral fertilization and green manure in the form of aftercrop and locally, powdered and granulated organic fertilizers (biohummus and Polli-Pam). The research included a period of long-terrn tuber storage (eight months) and the measurement step was one month. For control purposes, the measurement was done just after crop collection. The research was limited to two fractions of tuber: 30-40 mm and 50-60 mm. The conducted research results are that all the factors included into the experiment had statistically significant influence upon the potato skin punching force, i.e. the storage period, varieties, fractions and fertilization. The greatest value for the punching force was characteristic for the tubers of Salto variety after the last storage period, fertilized with mineral fertilizers. A greater value was obtained for the greater fraction tubers. The smallest value for the punching force was revealed in the case of Irga variety tubers, after four months of storage, fertilized with Polli-Pam. The following factors had statistically significant influence upon the tuber bending value: storage period, varieties and fractions. The bending was increasing systematically together with the storage period. The greatest bending value was revealed by Salto variety tubers. The tubers of the smaller fraction revealed smaller bending. The smaller bending value was revealed for Baszta variety.