Lime also contributes calcium necessary to minimize bitter pit. Established orchards should be soil tested every 3 to 5 years to maintain the desired pH and nutrient balance. Both calcitic and dolomitic lime are used in apple production. Dolomitic lime provides an economical source of the calcium and magnesium required for apple production. Bitter pit can be caused by low soil moisture, low leaf calcium, or an imbalance between calcium and potassium within the leaves.
Additional calcium can be soil or foliar applied.
Soil application of gypsum is the most effective way to supply calcium on established orchards. Gypsum provides more available calcium within the root zone or subsoil than surface-applied lime. However, gypsum is not a liming agent and cannot be substituted for lime to raise the pH. Moreover, gypsum will not correct bitter pit caused by extended dry weather for the current crop. Foliar application is the most effective way to increase calcium for the current growing season. Use calcium chloride when tissue analyses show a high nitrogen content.