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Outlook: Soil temps will dictate spring prospects

By Staff | Mar 29, 2014

URBANA, ILL. (University of Illinois) – While farmers hope the last of snow and cold for the season, but both air and soil temperatures remain below average in the Corn Belt heading into the second half of March, said a University of Illinois crop sciences researcher.

Emerson Nafziger said soils froze deeper than normal this winter and stayed cold into March. Frost is only now disappearing in the northern parts Corn Belt, which accounts for them staying cold even during a sunny day.

“Hopes that such deep freezing will relieve soil compaction from last year may not be realized,” Nafziger said, “while repeated freezing and thawing results in repeated formation of ice crystals that force soil particles apart

“Soils that stay frozen, don’t repeat this cycle often enough to do much good. The freezing and thawing of the surface soils that we’re seeing now will help loosen them some, but we can’t expect that effect to extend more than a few inches deep.”

According to the Illinois State Water Survey, minimum temperatures 4 inches deep under bare soil ranged from the low 30s in to the mid-30s the morning of March 17.

There was some sunshine on that date, and soils warmed to the upper 40s to low 50s in southern Corn Belt regions, but stayed in the low 30s in the northern region.

Best drying conditions

“Because water has a higher heat capacity than soil mineral matter,” Nafziger said, “cold soils do not dry out fast and wet soils do not warm up fast.

“We have seen some of the standing water in fields drain out this past week as soils thaw, but the drying process will be slow until soil temperatures start to increase

“Water loss rates are affected by soil texture and water content, but we would expect wet soil to lose a tenth of an inch or so in a day if the average soil temperature is 40 degrees and at least twice that amount if the average soil temperature is 60 degrees.

“So having soils warm up is the key to enabling them to dry out, though it has to stop raining for soils to dry, of course.”

While having low soil temperatures in March may not produce a optimism that planting will start early, Nafziger said it is not a good predictor of how the spring will go, or what kind of season growers will have.

“If we’ve learned anything in recent years,” he said, “it’s that what happens during the summer matters much more to the crop than what happens in March and April.

“We simply need to be ready to do fieldwork and plant as soon as conditions permit.”

The likely delay in the start of 2014 field work may mean re-prioritizing operations once soils dry out, Nafziger said. It has been common in wetter springs for the application of anhydrous ammonia to get under way before soils are considered fit to till or plant.

“That worked okay last year when compaction due to weather patterns did not cause much problem for the crop,” he said. “But we can’t count on that, and compaction from applying fertilizer or doing tillage in wet soils can leave soils in worse condition than before, even if the surface looks a little drier afterward.”

As a reminder, planting in early April almost never produces yields higher than planting in late April and can lower yields even when stands are good, he cautioned.

Planting in early April into good soil conditions, with soil temperatures expected to be on the rise after planting, is a sound practice, especially when there are a lot of acres to plant and starting early is the only way to finish on time.

“But ‘mudding’ corn into wet or marginally wet but cool soil conditions in early April,” he said, “is almost always a bad idea, with considerably more potential to do harm than to do good.”

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