Crop production, decomposition of organic matter, using ammonium-producing nitrogen fertilizers, and rainfall all lower soil pH. To maintain soil pH in the optimal range (6.5 to 6.8) for vegetable production, periodic application of lime is needed.
The primary form of agricultural lime is calcium carbonate (CaCO3). It is the carbonate (CO3^2-) part that brings up soil pH. Whenever lime is applied, a large amount of calcium is also added to the soil. The good news is that calcium is an essential plant nutrient. Several vegetable problems that we are familiar with are caused by calcium deficiency for example, blossom end rot of tomatoes and peppers, and tip burn of cabbages. However, it should be noted that excess calcium might interfere with plant available magnesium and potassium. Therefore, it is always better to keep a balance of those nutrients.
Some lime products are specified as dolomitic lime. Dolomitic lime is common in Indiana. These products have a higher magnesium content, often a combination of 50% calcium carbonate and 40% magnesium carbonate. If a soil test shows magnesium is low, applying dolomitic lime is recommended as it provides soil with both calcium and magnesium. If magnesium is already excessive in soil, Hi-Cal Lime that is almost exclusively comprised of calcium carbonate is a better choice.
Most ag limes are in solid forms that are made up of crunched limestone. Products vary in particle size. The finer the materials, the faster they dissolve, and the quicker they are capable of correcting soil pH. As a general rule, it takes 6 to 12 months for lime to completely dissolve. Therefore, fall is always a good time for liming. Liquid lime and pelletized lime are also commonly used for vegetable production. Pelletized lime is made by coating finely ground lime with lignosulfonate, thus it is not as dusty as solid forms, making it easier to spread. However, pelletized lime is more expensive, and does not react with soil faster than finely ground ag limes with similar particle sizes. Liquid lime is finely ground lime suspended in water. It reacts faster with soil than the solid form. However, liquid lime typically consists of approximately 50% lime and 50% water. Considering the large volume, it might not be feasible to apply liquid lime on a large area. More information regarding liming can be found at www.agry.purdue.edu/ext/forages/publications/ay267.htm.