As I write this article on a down right chilly day in October, I wanted to remind my readers of the importance of soil testing at this time of year.
Whether you are a pasture manager or home vegetable gardener, taking a soil test and amending the soil now will prepare the site for the spring growing season.
Why is soil testing important
Plants take up specific amounts of nutrients held in the soil profile, and scientists have split up these nutrients by those which are used the greatest and least, macro- and micro-nutrients, respectively.
Even though some nutrients are used less by plants than others, if one of the required nutrients is not present, it is referred to as the most limiting nutrient factor, and can prevent normal growth.
As a gardener, a soil test taken now will give you a good idea of the fertilizer needs of the garden for application in the spring. A soil test report will list the phosphorus, potassium, organic matter, magnesium, salinity, CEC (cation exchange capacity) and calcium content of the soil sample.
Since nitrogen is too unstable in the soil profile to be accurately calculated, current amounts in the soil are left off the test results and only suggested application rate estimates are listed.
It is usually a good idea to annually add organic matter to the soil to help build the soil structure and improve drainage and compost mixed into your garden in the fall season. All crops have a specific pH range which they prefer, and the level of soil acidity or alkalinity outside this range can cause plant nutrient imbalances and cause them not to thrive and become susceptible to disease.
Granulated limestone is used to raise the soil pH and sulfur is used to lower the pH, but since neither of these products have immediate results, fall application allows time for the chemical reaction to occur.
To get the full soil pH altering effects of the product, it is best to till in the appropriate application rate completely into the soil profile. Soil testing for pH sensitive crops such as blueberries is recommended on a yearly basis to monitor changes in the soil pH.
For an extensive list of plants and their preferred soil pH, see the following publication link: www.wvu.edu/~agexten/hortcult/homegard/pHpref.pdf.
Taking a soil sample
When gathering garden soil to send to the University Extension testing laboratory, try to get 12 random samples from the garden site. Each "core" sample should be taken from a slice of soil 6 inches deep.
I would use a spade to cut a slice of soil out of the soil profile, being careful to remove any surface debris prior to mixing to prevent inaccurate test results, which may indicate a higher organic matter content than is actually contained in the soil profile.
Page 2 of 2 - To get an average of the nutrient content of the sampling site, the random samples should be mixed together. The appropriate amount of soil to send for testing is no more than 2 cups. If testing multiple large gardens, it is best to send in separate soil samples from each of those gardens.
Once the samples are taken, the soil can be taken to your local county's University of Missouri Extension office for testing. Each basic soil test is $15, and soil test reports are typically mailed or emailed out to individuals within two weeks of receipt.
When taking the sample, make sure to write down the depth of the samples taken and the crop you would like to grow, this information will be made available to the testing lab for more accurate recommendations. For more information, visit http://extension.missouri.edu/p/G6954.