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Tips for Pulling Soil Samples

Tips for Pulling Soil Samples
Fall key time of year to pull soil samples.

One year ago, it was so dry that some postponed taking soil samples. Some that were taken produced results that were suspect due to the dry conditions. So besides the normal rotation of fields that you test every third year, every other year or every year, depending on how intense your soil sampling program is, you may have acres from last year that you want to test again this year.

You may do your own testing or hire a soils consultant to test for you. Either way, it's important to understand what goes into getting a good soil test that provides reliable results. That should give you more confidence in making and following recommendations for applying fertilizer based upon those tests.

Instead of being too dry, if rains continue or if late fall turns wet as some predict, the problem this fall could be finding a time when soils are dry enough to get a good test. Remember that if you normally test in the fall, test results will be most accurate if you always test in the fall, rather than taking some tests in the fall and some in the spring.

Here are tips offered by Purdue University agronomists. You can find more about soil sampling in the Purdue university Corn and Soybean Field Guide, 2011 edition, on pages 174-175.

Take 20 to 30 cores with a probe to form one sample. Mix all cores together and pull a sample from the entire set of cores.

While one sample can represent 20 acres, it's customary to divide that into smaller areas to sample today. The less uniform the ground, the smaller the areas you may want one sample to represent.

If fertilizer is banded when applied, take more cores than you would fi fertilizer was broadcast across the field.

Take soil samples to 8 inches deep in tilled fields. It's important to make sure you sample at exactly the same depth each time. Many consultants mark probes so they're getting the same depth each time.

In long-term no-till fields, you may want to sample at 0-4 inches and 4-8 inches separately. Certain factors, such as pH, tend to change faster and closer to the surface in no-till systems.

Sample lighter soils or sandy soils more often, say every one to two years even if you typically sample average soils every three years. These soils have lower nutrient holding capacity.
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