Jr. Stevens, Koske, Thomas J.
Knowing what is in your soil and what it needs is a basic and first step to a good crop and plant health. Our plants depend on the soils to provide adequate nutrients with which to grow. We must manage that soil balance for best growth.
Fall or early winter is a great time to do a soil test. It beats the spring rush and gives you time to find and apply what is needed. If lime is required to raise the soil pH, it must he applied several months before it is actually needed to support good spring growth. Lime takes several months to completely react to reduce soil acidity and may cause plant burning if applied when it is very warm outside.
A fall or late-season soil test can also show how well you came through the past growing season. Fall test values should come out mid-range to show that your fertility program was adequate and not too strong or weak. Too strong of a fertility program will cause a buildup of nutrients to test high or very high by fall. It’s not like having "too much" money in the bank; this can actually lead to growth problems or groundwater pollution. Too weak a program shows low to very low fall values in a fall test. This indicates that you had run out of good fertility before the end of the growing season and may have weakened the plants.
Soil is tested for potassium, phosphorus, calcium, magnesium and pH among other values in our ROUTINE SOIL TEST. These major nutrients fuel growth along with nitrogen. Since nitrogen is so transient, we just advise on its use, based on soil type and crop.
If your soil is similar throughout the property, one composite sample from the 4-to-6-inch profile can be used to advise on several crops. List all the crops that you will want fertilizer recommendations or that will grow in that soil sample type. Be crop specific because just listing "bermudagrass" may be interpreted as a pasture and not a lawn. You are allowed several crops for each sample, so you may put VEGETABLE GARDEN then CENTIPEDE LAWN and PEACH TREE all on one sample if all three crops are grown on this same soil type.
Soil samples can be brought to the local LSU AgCenter agricultural office or delivered to the LSU soil test lab in Sturgis Hall on the LSU campus in Baton Rouge. There is a $10 charge for this testing, and results can even be emailed back to you. For more information on the LSU AgCenter’s soil test service, call your local county ag agent or visit the website.