Magnesium Magnesium problems are not common and fields irrigated with water with greater than 8 ppm magnesium will not need any additional magnesium. Soil levels of less than 40 ppm may need additional magnessium. Problems with other micro-nutrients are not common and related to specific local conditions. Often micro-nutrient problems are related to an imbalance of other nutrients. In this case, applying the micro-nutrient in shortage will not solve the problem, since the imbalance of other nutrients still exists.
Tolerant varieties are the best solution.
Manganese problems resulting from excess levels of potassium Zinc problems form excess phosphorus Iron problems form low copper and high manganese levels in soil. Salts Potatoes do not tolerate much soluable salts in te soil and irrigation water. If the Ec of the soil is above 1.5 or the Ece of the irrigation water is above 1.0 yield will be limited. Colorado State's Potato Fertility Guide, click here. Adjustments for local conditions must always be made.