Pulverized limestone is the most common material used to raise soil pH. Limestone consists either of calcium carbonate (calcitic limestone) or calium/magnesium carbonate (dolomitic limestone). On soils low in magnesium, dolomitic limestone is the preferred form. Lime recommendations for raising soil pH are given in terms of pulverized limestone, but other liming sources can be used. (click here if you might use wood ashes)

Apply lime only if a need is indicated by the results of soil testing and the requirements of the plants being grown. Over liming can reduce nutrient availability, especially of micronutrients like iron, manganese, and zinc. Iron deficiency (chlorosis) of pin oak, for example, is common when soil pH is greater than 7.0.

Mineral Soils

The soils lab calculates lime needed for mineral soils using both the pH measurement and the Lime Index.

Most liming materials take several months to react with the soil, so for best results they should be applied and incorporated to a depth of 6 inches well before planting time. For established lawns or turfgrass areas, perennial vegetables and flowers, small fruits, fruit trees, and ornamental trees and shrubs, topdress applications of lime can be used but are much less effective than mixing lime with the soil prior to establishment. Lime recommendations are reduced for established plantings to reflect the fact that only the upper 1 to 2 inches of soil will be affected. The best time to apply lime to established turf is following core aeration for thatch control. Spread lime uniformly around other types of established plants. If possible, work it lightly into the soil, while avoiding the disturbance of plant roots.

Organic Soils