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More on Lime and Successful Food Plots

by Wiley C. Johnson, PhD
Date Posted: 01-01-2010

Pelleting does not mean that less lime is required to attain needed acid neutralization.

Every time I ask our consultants about their most frequent questions, the answers are almost always questions about lime. I suspect some of you think that lime is all I am concerned about since it is the subject of so many of my articles. If you are one of these, please bear with me and consider that our readers are continually changing. There are some who have not read my lime lecture. Also, the essentials for having successful food plots are a suitable soil, adequate fertility, proper soil acidity (pH) and quality seed of the best plant varieties. Proper soil acidity is attained by correctly applying lime. Adequate soil fertility is maintained by soil testing and following recommendations. Use Imperial Whitetail seed blends to be assured of the best varieties and seeds. The rest of this article will be on lime.

Almost all material applied as “lime” is ground limestone rock. Agricultural lime is the trade name of this material.  Limestone rock is either calcite (CaCO3) or dolomite (CaCO3 plus MgCO3). The MgCO3 content in dolomite is variable. Calcitic and dolomitic agricultural limes are equally effective liming materials. Use whichever is most readily available in your area. How well and how fast lime corrects excessive acidity is determined by two factors.  The first is the purity of the limestone rock. Most state laws require a minimum CaCO3 equivalent in neutralizing effectiveness of 90 percent for a product to be legally sold as agricultural lime. The second factor in determining lime’s effectiveness is the fineness of particle size. Generally, the finer the better. Again, state law sets the minimum standard. Alabama requires 90 percent pass a 10-mesh screen and not less than 50 percent pass a 60-mesh screen. Other states’ requirements are similar. Commercial agricultural lime rarely fails to meet or exceed these minimum standards.

Some ordinary limestone rock is ground extremely fine. Most of this ultra-fine lime is formed into pellets. Such lime reacts almost immediately and this, plus convenience of application, are the only advantages of the more expensive finely ground and pelleted lime. Pelleting does not mean that less lime is required to attain needed acid neutralization. Some ultra-fine lime is mixed with clay and suspended in water. The advantage of this slurry is only application convenience. However, a ton of slurry (liquid lime) is a lot of water and not nearly effective as a ton of ordinary ground limestone. For our purpose, to establish and maintain quality food plots, the best liming material to use is ordinary agricultural lime.

Lime neutralizes soil acidity as the lime particle comes in contact with acid soil particles. Also, lime pretty much stays where you put it. If it moves, you have to move it. This is why it is so important when first establishing a food plot that you thoroughly mix necessary lime in the surface 6 to 8 inches. Later surface applications of lime are mostly effective by counteracting the acidifying effect of surface applied fertilizers. This delays the entire root zone becoming more acid.

There are several other limestone products that are primarily for industrial uses but will neutralize soil acidity and are sometimes used on soil. The most common of these are burnt or burned lime, CaO, and hydrated or slaked lime, Ca(OH)2. Burnt lime is ordinary limestone heated to very high temperatures. This is bad stuff — very caustic. Flaked lime is CaO to which water has been added to form Ca(OH)2 and is safe to use. There are also industrial by-products such as flue-dust and basic slag, which are effective and may be locally available. Before using these products, check with a local expert, such as the county agent, for information and advice on a specific product.

Lime not only neutralizes acidity, it also provides calcium, and if dolomite is used, magnesium is also provided.  These are essential plant nutrients but available elsewhere, and the value of their addition in lime is secondary to that of acid neutralization.

In summary, lime is applied to correct excess soil acidity. To do a good job, first get a soil test to determine how much lime is needed. If this is a new planting, apply about 75 percent of the recommended amount before any land preparation and then incorporate to a depth of 6 to 8 inches. Mix as well as you can since this is your only opportunity to lime this zone until you plow again. After initial preparation, fertilize and add the remainder of the recommended lime and incorporate shallowly (1 to 2 inches) just prior to planting. The best liming material to use is ordinary agricultural lime, either calcite or dolomite. Lime can make or break the success of a food plot.

Reprinted with permission of the Whitetail Institute of North America.  For more info on this article and other
related topics contact them at (800)-688-3030 or visit their website at www.whitetailinstitute.com