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College of Food, Agricultural, and Environmental Sciences


Research Determining Best Time to Subsoil

November 17, 2005

COLUMBUS, Ohio — To capitalize on the benefits of deep tillage, also known as subsoiling, when the technique is performed may be just as important as how and where it's practiced.

The most common time of year to subsoil is in the fall immediately following harvest. But sometimes growers are forced to delay subsoiling until mid-winter.

Randall Reeder, an Ohio State University agricultural engineer, has launched research at the Ohio Agricultural Research and Development Center's Northwest Agricultural Research Station near Hoytville, Ohio, to determine if winter subsoiling is just as beneficial as subsoiling in the fall.

"The best time to subsoil is in the fall, but sometimes because of late harvest, unsuitable weather or other circumstances, growers delay subsoiling until January," said Reeder. "No research data exists on subsoiling in mid-winter in Ohio. We hope the weather cooperates and gives us an opportunity to conduct the research."

Subsoiling with a low disturbance tillage tool is a conservation practice that breaks up soil 12-18 inches deep, allowing increased water movement, better aeration of the roots and access to additional minerals and nutrients for plant growth. The benefits associated with subsoiling are the alleviation of soil compaction and improved corn and soybean yields. By comparison, conventional tillage breaks up the soil 6-8 inches below the surface, and in areas compacted by heavy combines and grain carts, such a practice is not adequate.

Ten years of Ohio State research has shown that subsoiling works well on the silty clay loam soil commonly found in northwest Ohio.

Reeder said the soil type tends to "compact naturally," creating drainage problems that are only compounded with additional compaction from heavy machinery.

"The culmination of Ohio State research has proven the benefits of subsoiling in November. Now we want to find out if January subsoiling can be just as effective," said Reeder.

Subsoiling is best practiced in the fall because the freezing and thawing cycles associated with the onset of Ohio's winters help to settle the soil prior to planting in the spring. One of the concerns of delayed subsoiling is running the risk of a loose soil structure that is not conducive to seed germination and root growth.

"The longer a grower waits to subsoil, say as late as March, the higher the risk of decreased yields," said Reeder.

Like other production practices, subsoiling has its advantages and disadvantages. Low-disturbance subsoiling equipment is capable of breaking up deep soil while leaving surface residue virtually untouched, affording the farmer the benefits of both deep tillage and no-till. Residue from the previous crop remains on the surface and the following season's crop is planted directly into it, minimizing soil erosion.

"A grower has three options with subsoiling: not to subsoil at all, subsoil every year, or subsoil occasionally," said Reeder. "Our research has shown that subsoiling every two or three years produces the same benefits as subsoiling every year, which is good news for farmers because of the expense. Note that our research plots are farmed with relatively light equipment, so we are not recompacting the soil the way many farmers do."

A disadvantage of subsoiling is the increased horsepower that is needed compared to no-till or chisel plowing, raising production costs for the farmer. But the benefits of subsoiling can outweigh the extra expense. Based on Ohio State research on Hoytville soil, subsoiling can increase yields anywhere from 5 to 10 percent. For 1,000 acres of corn, that can translate into a $15,000 to $30,000 savings for the grower, said Reeder.


Candace Pollock
Randall Reeder