Information on Lime for Soil

How Soil pH Affects Plants

• The pH of soil has a dramatic affect on the growth of plants. Most crops grow best in the pH range of 6.0 to 6.8, according to University of Nebraska soil scientists. When pH falls below this range, some nutrients, such as phosphorus and molybdenum, are not available for uptake into plant structures. Other nutrients, such as aluminum and manganese actually become toxic to plants when pH falls below 5.0. When pH levels drop, soil becomes acidic. Ammonia-based nitrogen fertilizers lower soil pH.

Adjusting Soil PH

• Many farmers and gardeners adjust the pH to help certain types of plants grow. Plants such as camellia, birch, barberry, soybeans and blueberry all prefer an acidic soil pH below 7.0. Other plants, such as juniper, spirea, carrots and cabbage prefer an alkaline soil, that is, one with pH values above 7.0. Before adjusting your soil's pH, do a soil test to see what the current pH level is, and consider what types of plants you plant to grow.

Types of Lime

• Lime is a term used for the many compounds used to adjust the pH of soil to enable plants to thrive. They may contain both calcium or calcium and magnesium in combination. Calcic limestone, or calcium carbonate, is almost pure calcium in a powder form. Dolomitic limestone contains calcium and limestone in about equal amounts. Burnt lime, calcium oxide, is a quicker-acting form of lime that is very caustic and must be used with care, according to West Virginia University Landscape Architect Clifford W. Collier. Hydrated lime is another type that works more quickly than calcium carbonate.

How To Add Lime To Soil

• The best time to add lime to soil to raise pH is at the time of planting. Generally, you add the lime to the first 6 to 8 inches of soil. Generally, 2 to 3 lbs. of lime for every 100 square feet raises the pH one full point. Use small amounts of lime gradually and test soil to see how much you are raising the pH number. It may take months to see the effects of adding lime to raise the pH of soil Do not overlime the soil, which can injure plant growth.