Soil testing when it is wet
Barton County Extension Agent
I can see it on a wanted poster now – WANTED, WET OR DRY, SOIL! Notice, I didn’t say dead or alive, I am hoping your soil is alive. But, a little fertilizer may bring it to life. So how much should I put on and what kind? You can find that out by bringing a soil sample to our office.
It’s that time of year when gardeners are primed and ready to get their fingers in the soil, better known as dirt. With spring finally here, many gardeners may be thinking about getting a soil test. But, we often delay getting the soil sample in the autumn season when the soil is fairly dry and wait until now when the soil may be wet from winter snows or rains.
It is still possible to get a soil sample and accurate results if you sample the soil and allow the soil to dry for 3 to 4 days before sending it in. Never use any type of artificial drying such as putting the soil in an oven or microwave to dry it out. This may change the nutrient availability levels and give an inappropriate reading. Air drying, however, will not change the analysis of the sample and will prevent problems when we try to mail a wet sample (as well as increasing the cost of shipping or mailing).
Results can be returned to you quicker since soil samples will need to be dried at the lab before the analysis can be run and that may take a few extra days to complete. Also, make sure that soil samples are collected in a clean container. Wet soils may soak up more of any extraneous materials that may be adhering to buckets or cans when the soil is wet and this may also lead to an inaccurate reading of soil test results. So a plastic bucket is preferred over rusty metal, etc.
A soil test provides a starting place for a soil improvement program for the home gardener. Unless you know the problems in your garden soil, you are only guessing when you apply fertilizer.
While I am on this topic I should point out that I see as many, or even more problems associated with vegetables and fruits where people apply too much fertilizer or manure and get test levels so high that they tie up micro-nutrients. This seems to be especially the case where the soil is either really alkaline, such as pH of 8.0 or more, or extremely acid such as less than 5.0. For most garden crops, 6.5 is about an ideal soil pH.
Proper collection of a representative soil sample is important for accuracy and analysis of the test results. You will need a trowel, shovel or soil testing probe and a clean container. We have stainless steel probes that we loan out from our office if needed.
First, identify uniform areas to be tested. For example, a separate soil test should be done for a garden or lawn, or between the front lawn and back lawn. Also if there are noticeable differences in soil type or if you have an area that seems to have a problem, sample those separately. Avoid sampling areas that might give misleading results. Information for those spots should be separated.
Once you have identified a somewhat uniform sampling area, which may be the entire garden, take at least 5 cores or slices. Some people will say 10, depending on the size of your garden. Collect a vertical sample starting at the surface and go 6 inches deep. Try to stay uniform in depth with each core. Some labs may tell you to go as deep as 12 inches, but very few of our garden crops actually have many roots to that depth because we water enough that they stay near the surface.
As you pull each core or spade slice, remove as much plant residue from the sample as possible. Then, mix all these cores together thoroughly. When you are finished, bring a pint of soil (2 cups) to our office in a bag.
A routine test will only cost you $10. If you have two or more samples, they are $9 each. Turn around time is typically about a week.
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