How to calculate limestone application

Published on Monday, 17 April 2017 10:51 - Written by CHAD GULLEY, Texas A&M AgriLife Extension Service

It is common to see soils in East Texas that fall into the acidic side on the pH scale. The pH scale runs from 0 to 14, with 7 being neutral. Soils below 6.5 are considered acidic, while soils above 7.4 are considered alkaline.

Limestone is used to raise pH in home lawns, gardens and pasture situations. A soil test will determine pH levels as well as nutrients present or lacking in the soil. The soil test typically cost $10, depending on the analysis you desire. Optimum uptake of most nutrients for most crops occurs as a soil pH of 7.0.

Various factors, including environmental, climatic and cultural factors, affect soil acidity. Applying limestone or other material to change the pH to a more neutral level allows plants to utilize nutrients available in the soil.

Limestone quality is important. All limestones are not the same, and may react more or less efficiently based on particle size and neutralizing value of the limestone material. Smaller particles have more surface area, react more rapidly to change the pH and have a higher efficiency rating. The ability of a limestone to neutralize soil acidity also depends on its effective calcium carbonate equivalence (ECCE) or neutralizing value.

ECCE combines fineness efficiency rating and the calcium carbonate equivalence to estimate the percentage of effective limestone in a given product. The percent ECCE of a product should be available from the vendor. This is important because limestone rates by soil testing laboratories are based on use of 100 percent effective limestone (dry weight basis).

Agricultural grade limestone generally has an ECCE value of 50 to 70 percent. So if a soil test recommendation for lime is 1.0 ton/acre, the actual application rate of a limestone with an ECCE value of 60 percent would be 1.67 tons/acre. Limestones with an ECCE value of 95 to 100 percent are becoming increasingly available in the market. In many cases, limestone with an ECCE value of 95 to 100 percent that is priced slightly higher per ton is a better buy than standard agricultural grade since a lower application rate is needed.

To figure how much limestone is needed according to the ECCE material purchased, follow the soil report and you may need to use your mathematics skills. For example, if 1 ton/acre is needed and an 80 percent material is purchased, divide 1 by 0.80 to apply 1.25 tons/acre. If a 60 percent material is purchased, 1 divided by 0.60 is 1.67 tons/acre material that would need to be applied to the area. If 100 percent material is purchased, 1 divided by 1.00 shows 1 ton/acre would be needed. The ton/acre basis is generally used in pasture or hayfield situations.

Limestone needed for a lawn or garden would be broken down into smaller application rates. For home lawns, it is generally expressed as so much limestone material per 1,000 square foot basis. When purchasing bags of lime for your lawn or garden, read the analysis on the bag to determine the ECCE value of the material purchased. ECCE values will vary. Depending on how acidic your lawn or garden may be determines the application rate.

Limestone can be applied at any time. Several factors should be considered when making an application of lime. Soil moisture is critical, thus rainfall patterns are needed in the area to help incorporate the limestone into the soil. As mentioned earlier, particle size is important as well, so enough time for the material to begin breaking down into the soil is needed for the lime to react in the soil. Limestone should be applied to soils that are firm enough to hold up the spreading equipment.

Limestone particle size may also dictate when it is applied. Finer limestone material can be applied most of the time, but wind may be a factor to get an even distribution of the material. Applying finer limestone materials may require a calmer day when wind is not a factor. How dry the limestone material is will also be a factor to consider when applying. Moisture content of 7 to 9 percent in fine limestone is needed to minimize dust and achieve uniform spreading of the material.