Eddie Baggs: Soil testing important to plant growth

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Most of the soil in Denton County is alkaline and will never need lime application. However, there are a few exceptions, with several pockets of acid soil existing in the county. Soil testing is recommended if landowners suspect that an acid soil is in need of lime.

For most plants or crops, a pH of 5.5 or lower would be needed before considering a lime application. Lime is a soil amendment that will drive the pH of soil upward to a more correct or plant-friendly pH.

The soil pH scale rates from 0-14. Soil between 6.6 pH and 7.3 pH is considered to be neutral, while soils rated below 5.5 pH are acidic and soils above 7.4 pH are alkaline.

If it is determined that lime should be applied, be aware that lime comes in various forms and qualities.

The two most important factors to consider before purchasing lime are calcium carbonate equivalent (CCE) and fineness efficiency. CCE is a measure of the acid percentage the lime will neutralize when pure calcium carbonate (lime) equals 100 percent. Fineness efficiency relates to the fineness of the grind, graduation or particle size. The higher the mesh number the lime will pass through, the smaller the particle size and the faster the lime will react in the soil.

Both of these factors are used to calculate the effective calcium carbonate equivalent (ECCE). This is the figure most often used to “grade” lime — basically, the finer or more powdery, the better.

An ECCE of at least 50 percent is needed for the lime to be considered good for agricultural purposes. If the ECCE is less than 50 percent, it is either too impure or not finely ground enough. The higher the lime’s ECCE value, the less you will need to apply to achieve the same result.

The lime’s moisture is also important since the weight of the water replaces or adds to the amount of material purchased and hauled. It also can cause the material to clump and not spread uniformly. Remember that trucking will probably be the highest cost portion of liming. The closest source may be the best.

Another reminder is intended for the impatient producer: Lime does not affect change quickly, even if the highest quality. A change in pH and plant growth may take anywhere from four months to two years. Lime products that do change the pH very quickly are not desirable. If the pH changes too quickly, many plants will not be able to acclimate and may die, even Bermuda grass. 

Soil pH can change from year to year due to environmental conditions, production practices and climate. It is recommended that a simple soil test be conducted at least every three years to track soil pH. 

To have soil tested for pH, download instructions and forms at http://soiltesting.tamu.edu and send to the soil-testing lab at Texas A&M University.

 

EDDIE BAGGS, extension agent with the Texas AgriLife Extension Service in Denton County, can be reached at 940-349-2880.


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