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Corn+Soybean Digest

Snub Subsoiling

If you're a true no-tiller, chances are you don't have soil compaction. Yet some no-tillers, believing they have compaction problems, are subsoiling their fields. University of Kentucky (U of K) research shows it's probably not necessary.

“No-tillage corn production has become very popular in Kentucky and many fields have received little tillage for 10-20 years,” says U of K agronomist Lloyd Murdock. “As a result, many producers wonder if annual traffic by heavy equipment has created compaction.”

Murdock says some producers are routinely subsoiling every second fall after soybeans in a corn-wheat-soybean rotation. He points out that subsoiling implements such as the paraplow perform subsurface tillage while preserving the surface mulch layer.

“But many of the producers who regularly subsoil do not take field measures to determine whether compaction exists,” Murdock notes. “This is unfortunate, because our research has shown that subsoiling fields that are not compacted only increases costs. It does not improve grain yields.”

In Murdock's research, he took penetrometer readings on three long-time no-till fields. The fields had subsoiled and non-subsoiled areas side by side.

He found meaningful compaction in only one, small non-subsoiled area of poorly drained soil.

Most of the non-subsoiled readings showed resistance to be less than 300 psi, which is not considered compacted. The university recommends subsoiling only if 50% or more of the penetrometer readings are 300 psi or more.

On average, yields from the subsoiled areas were 1.3 bu/acre higher than those of the non-subsoiled. But that wasn't statistically significant — and definitely would not cover the $10/acre cost of subsoiling, says Murdock.

In northwestern Ohio, many farmers began no-tilling in the late 1980s. “After a number of years with no-till, we were getting a large buildup of residue and the ground was staying wet and cool in the spring,” reports Bill Rohrs, coordinator of the multicounty Conservation Action Project. “Most producers began doing some form of tillage to dry and warm the ground.”

Rohrs recently took penetrometer readings on 25 of those fields. He found a compacted layer in nearly every case.

He found no compaction on a long-time no-till farm where there had been no tillage.

“For the strict no-tiller who doesn't go on the ground when it's wet in either the spring or fall, there probably won't be a compaction problem,” says Rohrs.

At Walnut, IL, producer Chris Von Holten has been strictly no-tilling 100% of his ground since 1988. He recently did a random compaction check with a penetrometer. The readings all were below 300 psi — except for the edge of a field where he loaded corn last fall.

Rod Grunloh, of Bureau Service Co., Princeton, IL, does penetrometer readings on many fields, both tilled and no-till, each fall. “We find compaction where tillage has been performed, but no meaningful compaction on true no-till fields,” he reports.

Penetrometers sell for about $200. Dickey-John is one of several manufacturers. Phone 800-637-2952 for a local dealer.

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