The following should be considered when developing a fertilizer program for potato production.
pH
pH is an important factor in any fertilizer program and in controlling common scab. As pH increases to near 6.0 plant nutrients also increase and toxic elements become less available, thereby providing optimal growing conditions from the standpoint of nutrients. Where scab is not a problem, pH levels should be as high as possible (up to 6.0). Soil pH should be between 5.0 and 5.2 to control common scab. Scab resistance varieties should be grown at high pH levels. Potato breeders are working on developing scab resistance lines and in the future hopefully we will not have to adjust the pH downward to control common scab. See more here.