Dolomitic Lime Amendment Affects Pine Bark Substrate pH, Nutrient Availability, and Plant Growth: A Review

Dolomitic lime (DL) is one of the most commonly used fertilizer amendments in nursery container substrates. It is used to adjust pH of pine bark substrates from their native pH, 4.1 to 5.1, up to about pH 6. However, additions of DL have been shown to be beneficial, inconsequential, or detrimental depending on the crop to which it is applied and irrigation water quality. Carbonate ions from DL cause a rate-dependent change in pH. Dolomitic lime can adjust pH of pine bark up to approximate to 6.5, after which there is little change regardless of how much additional DL is added. Changes in pH affect the rate of nitrification in pine bark substrates. The rate of nitrification can impact the quality of some plants that are sensitive to ammonium toxicity, as well as affect nitrogen leaching from containers. Changes in pH also affect micronutrient availability in pine bark substrates. Dolomitic lime provides an abundant source of calcium (Ca) and magnesium (Mg) for plant uptake. However, the additional Ca and Mg might also suppress potassium uptake in plants.