Understanding Your Soil Test Results

So, you did a soil test with Clemson Extension. Now what? Within 7 to 14 days, a copy of your soil analysis will be emailed or mailed directly to you from the Agricultural Service Lab. The soil analysis will have the soil pH value and a bar graph that represents the amount of soil nutrients found in the soil.
The section at the bottom of the first page shows how much lime (if needed) to add for each 100 square feet and refer you to specific comments on the last page.
The comments section tells you what type of fertilizer(s) you need, how much you need, and when to apply it. These recommendations are specific for the type of plants you want to grow as indicated on the soil test record sheet.
Preferably, the bars representing the nutrients on the soil report should be at the upper end of “sufficient”, and the soil pH in the correct range for the specific plant or crop. Applying the recommended lime and fertilizer ratios should accomplish this and allow for best plant growth.
Soil pH measures how acidic or alkaline your soil is, which directly affects nutrient availability. The pH scale ranges from 0 to 14. Numbers from less than 7 are acidic, 7 is neutral, and numbers greater than 7 are alkaline or basic. Different plants thrive best in different soil pH ranges. Blueberries, azaleas, rhododendrons, and conifers grow best in acidic soils with a soil pH of 5.0 to 5.5. Vegetables, ornamentals, and most turfgrasses do best in slightly acidic soils with a soil pH of 6.0 to 6.5. Lime can be applied as pelletized dolomitic limestone, but that takes several months to totally dissolve and change the soil pH. Faster acting limestone is available, but it does cost more, however this limestone does not last as long in the soil.
Nutrients are divided into different categories based on the amount of nutrients required. Nitrogen, phosphorus, and potassium are primary nutrients and are needed in large quantities. Calcium, magnesium, and sulfur are secondary nutrients which are needed in lesser quantities. Zinc, manganese, copper, and boron are micronutrients which are required by plants in very small amounts.
Most secondary and micronutrient deficiencies are easily corrected by keeping the soil at optimum pH value. Dolomitic limestone can raise the soil pH of acidic soil and is the primary source of calcium and magnesium.
Remember to follow the recommendations in the comments section as to what you need to do to get your soil ready for the upcoming planting season.
For more information on Soil Testing, please visit the HGIC website at hgic.clemson.edu. Tune in on Tuesday nights to watch “Making it Grow” at 7pm on SCETV or mig.org. Email Outen at [email protected]
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