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Commercial Horticulture > Comm Hort Blog > Posts > Soil Testing to Improve Your Next Garden

We receive a lot of questions at the Extension office each year from farmers and home gardeners with many kinds of problems. Oftentimes the problems in a field or garden fall into one or more of the following categories: disease, insect, weed, wildlife damage, nutrition, or disorder. Many times during the year gardeners will contact the Extension office with a plant problem thinking it is a disease when in fact it is a disorder.  Examples of plant disorders could be problems related to heat stress, cold stress, lack of moisture, too much moisture, or too much shade. One season's production will be different from another, but there are things that can be done to encourage better quality crops each year.

I would like to encourage growers to have a soil test on their fields or gardens. A soil test is basically an analysis of the nutrients in your soil. With this analysis, we can determine what nutrients are needed, and oftentimes, not needed in your field or garden. The goal is to apply the needed nutrients for the crops being grown. Crops may not grow well with too little or even too much of certain nutrients. All crops will not need the same amounts of nutrition, and too much of certain nutrients can often times make them less productive. The soil test will tell us what nutrients to apply to what crops and the amounts needed. 

A common recommendation would be to apply half the nitrogen, all the phosphorus, and half the potassium at planting. Then add the remaining nitrogen and potassium in one, or even two more, applications later in the season. Without a soil test we would be guessing at how much and what kind of fertilizer to use. The soil test will explain when to apply the nutrients and you can always call the Extension office with soil testing and fertility questions. I always recommend commercial vegetable farmers test their soil every year. I sometimes suggest home gardeners test each year as well, depending on what nutritional problems they have been having in their garden. Unless a nutritional problem has occurred, testing every 2 or 3 years is often what many gardeners practice.

Our soil test form can be found on our web site at or by visiting your local Extension office. This form has instructions for collecting soil samples, as well as information on how to send the soil samples to the lab in Auburn. Basically all you need is to collect several subsamples from your field or garden, mix the subsamples together, and send a sample of that mixture to Auburn University for an analysis. Taking several subsamples and mixing them together provides an average soil sample from your field or garden which results in a more accurate sample than from taking only one sample from one spot. If more than one field or garden is tested, the same procedure of collecting subsamples and mixing them will be conducted.  For example, if you have three garden spots you may send three soil samples in three separate containers for testing. There is a $7.00 charge per sample and you get the results back in about a week.  When is the best time of year to have a nutrient analysis on your soil? If you are having problems or have not had your soil analyzed in a few years, I would do a soil test as soon as possible. However, I like sending soil tests in the late summer and early fall before I plow the garden under and plant cover crops. It takes time for lime to start working in the soil. If lime is needed it could be applied, plowed in, cover crops planted, and the garden would be in good shape for the spring. If you have questions about your soil test results, give us a call at your local Extension office.

Chip East
Regional Ext. Agent, ACES



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