Topics : Soil Fertility for Forage Crops : Pre-Establishment
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There are several important considerations for liming practices. The rate of limestone required must be determined by a soil test that includes both a soil pH and lime requirement test. Limestone should be applied at least six months to a year ahead of seeding. If the test calls for more than 4 tons of limestone per acre the application should be split with half of the limestone plowed in and the rest worked into the surface with secondary tillage. For low rates of limestone or if a split application is not possible, the limestone should be worked into the surface rather than plowed down. This will assure that the surface soil, where the seedling is developing and where the nodulation begins in legumes, has the proper pH. Not all limestone is equal. The rate of limestone application should be adjusted for the neutralizing ability of the limestone. The neutralizing ability is given as the calcium carbonate equivalent (CCE) of the limestone. All soil test recommendations are made on the basis of 100 percent CCE. This does not mean that only 100 percent CCE limestone should be used. The rate of application for any limestone with a CCE higher or lower than 100 must be adjusted. The formula for making the adjustment is as follows:
Adj. Limestone Rec. = 100 x Limestone Rec./CCE
An explanation of how to make this adjustment and a table for making this adjustment is provided on ST-2 "Fertilizer Recommendation Table" sent out with each soil test run by Penn State.
The fineness of the limestone is also an important quality consideration. The finer the limestone is ground, the more rapidly it will react in the soil to neutralize the acidity. To be effective a minimum of 95 percent of the limestone should pass a 20-mesh screen, 60 percent should pass a 60-mesh screen and 50 percent should pass a 100-mesh screen. Generally there is little practical advantage to using a liming material that exceeds these fineness standards. It will probably only be advantageous to pay more for a finer limestone in an emergency where the pH is very low and rapid neutralization is required.