Don't guess, soil test

By: Clemson University Cooperative Extension

(Columbia) Jan. 10, 2006 - A lot of things have changed over the last 10 to 15 years, but there is one thing that is still very accurate in this technology age.  That is, Don't Guess, Soil Test.  This slogan has been used for alerting farmers and gardeners to evaluate nutrient levels in the soil for plant growth for years.

There are 16 essential elements or nutrients needed for plant growth.  They are grouped into three categories based upon the amounts found in the plant and not the level of importance to growth. The major elements are nitrogen, phosphorus, and potassium.  The secondary elements are calcium, magnesium and sulfur.  The largest group by number is micronutrients and they are boron, copper, manganese, zinc, iron, molybdenum and chlorine.  That is only 13. The other three elements are carbon from the air and hydrogen and oxygen form water.

All of the major and secondary nutrients levels are tested in soil samples. Recommendations are given based on the amount of fertilizer needed to provide the proper level of nutrients for plant growth.

The soil pH is one of the most important reactions in the soil as it relates to nutrient uptake by the plant.  The term, soil pH, defines the hydrogen ions in the soil. The pH ranges from zero to 14 with 7.0 being neutral.  Values below 7.0 are acid and those above are basic.  Most plants grow best when the soil pH is in the 6.0 to 6.5 range.  Some plants prefer a pH of 5.0 to 5.5 while other prefer a pH of 6.8 to 7.0.  Requesting recommendations for different crops when the soil is tested, will indicate the correct pH value for the crop.

When the pH falls below 6.0, it decreases the availability of most major and secondary elements to the plant.  This will also happen with high pH.  Most micronutrients availability will increase with pH below 6.0 which could pose a problem of toxicity with these elements.

Measuring the pH alone will not give you the information you need to properly apply limestone.  The Apotential@ acidity or the buffer pH is needed also.  A soil with a low buffer pH will require more limestone to neutralize the acidity than a soil with the same pH and a high buffer pH.

Getting your soil tested is simple.  First, you need to get a representative sample of the area you are testing.  Take an equal amount of soil, four to six inch depth, from 10 to 12 locations in the area.  Mix together and collect at least a pint of soil.  Carry the sample to your local Clemson Extension office for processing.  The cost of a soil test is $6.00.  You can get up to three recommendations per sample and the results will be mailed to you.

Don=t Guess, Soil Test today so that you have nutrient healthy crops, beautiful landscapes, turf areas and vegetable gardens this spring and summer.


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