Still time to test soils this spring?

The late, wet fall did more than stretch out harvest. Some fields scheduled for soil testing weren’t sampled. Can you still pull them now? Or should you wait until fall, basing fertilizer rates now on previous soil tests?

As it turns out, there’s a difference of opinion. Nearly everyone agrees it’s best to sample soils at the same time of year each time. The rub comes when weather interferes, as it did in fall ’09.

Darrell Shemwell believes in sampling at the same time of year so strongly that he would postpone soil testing. “You should try to sample your fields at the same time of year [each time] to minimize variability that occurs and maintain consistency in your trends,” says Shemwell, Poseyville, branch manager for the Posey County Co-op, and a Certified Crop Adviser.

“If I wasn’t able to get all of my fields sampled last fall, I would probably wait until this fall. I would make this spring’s fertilizer recommendations from my previous [soil] samples, taking into consideration the yield of the previous crop and nutrient removal for that crop.”

Shemwell assumes, however, that your last set of soil samples isn’t over four years old.

Key Points

• Experts agree it’s best to pull a soil sample at the same time every time.

• Some say rather than guess, sample this spring if you didn’t test last fall.

• Others tweak rates based on history and crop removal, then sample in the fall.

Pull samples now

Jeff Nagel leans toward pulling samples this spring. He’s a Lafayette-based agronomist for Ceres Solutions, and also a CCA. “Seasonal fluctuation of test levels does occur, but in the big picture, it can be managed,” he says.

Soil test levels for potassium tend to be slightly higher if samples are pulled in the spring, Nagel observes.

“If you think there may not be enough time this spring to test and get fertilizer applied, you could make an annual application of replacement nutrients either over the winter or in early spring,” he continues. “Then you could test next fall.”

Test anytime

Greg Kneubuhler agrees that maintaining consistency on timing helps keep your soil tests uniform so it’s easier to pick up trends. However, he’s also adamant that it doesn’t matter when you pull samples, if you pull at the same time of year.

“There’s absolutely no bearing on the time of year when soil samples are taken,” says Kneubuhler, who operates G & K Concepts Inc., Harlan. He’s also a CCA. “We take soil samples all year long.

“With costs where they are today, to make a ‘guess’ at what needs to be applied is not in your favor. You’re better off to pull samples when you can in the spring to make adjustments as needed,” he says.

Other factors influencing soil tests include moisture content of the soil and weather impacts. For example, if samples are pulled when it’s extremely dry, salts pulled up by the conditions could affect cations in the soil. That would be an important factor to consider when evaluating those soil tests, he concludes.

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CONSISTENCY COUNTS: Pulling soil samples at the same time of the year and at the same depth each time produces more consistent results.

This article published in the February, 2010 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.