For every $1 spent on drainage technology, producers get $3 to $4 back in corn and soybean profits, according to long-term Ohio State University research.

Twenty-five years of field studies (from 1984 to 2009) at the Ohio Agricultural Research and Development Center (OARDC) Northwest Agricultural Research Station in Hoyvtille showed that subsurface drainage significantly improved corn and soybean yields on poorly drained soils. Add crop rotation and some sort of conservation-tillage practice and production just keeps getting better, researchers say.

“Overall, a farming system that includes subsurface drainage, crop rotation and no-till or another conservation-tillage system provides the best long-term economic and environmental benefits for the farmer,” says Randall Reeder, an Ohio State University Extension agricultural engineer.

Reeder says that the long-term research was designed to evaluate the effects of drainage, tillage systems and rotation on corn and soybean yields to provide a better understanding of how to increase yields while maintaining sound conservation practices.

The research was a randomized experiment with three replications. It was comprised of two drainage treatments — subsurface drainage and no subsurface drainage. Each plot was further divided into four crop rotation treatments: continuous corn, continuous soybeans and a corn/soybean rotation with each crop every year. The plots were further divided into a series of tillage treatments: plow, ridge-till, no-till, strip-till and deep tillage, or subsoiling.

Plowing was included throughout the 25-year study. Ridge-till was compared to plowing from 1984 until 1995. No-till was initiated in 1992. For the past 11 years, the tillage systems consisted of plow, no-till, subsoiling and strip-till (for corn after soybeans).

Researchers found that subsurface drainage offered higher yields for corn and soybeans. The average increase in corn yields ranged between 24% and 39% for different tillage systems. Soybean yield increases ranged between 12% and 45%.

“Drainage removes excess soil moisture in the spring, allowing earlier planting most years, which can lead to higher crop yields,” said Larry Brown, an Ohio State agricultural engineer. “Many growers see a lot of wet springs. It’s difficult planting in cold, wet, clay soils, which is why drainage pays.”

The research results also pointed to the importance of crop rotation.

“For corn, rotation with soybeans significantly increased yields, about a 25-bushel-per-acre advantage over continuous corn. The results support the long-known yield advantage provided by crop rotation,” Reeder says. “For soybeans, the benefit was less, but still noteworthy, about a 2-bushel-per-acre advantage.

"It’s logical that rotation allows earlier planting of corn, but for soybeans there’s less of a timely planting issue.”

Results of the various tillage systems were less straightforward.

In the 12 years that ridge-till was compared to plowing, there was no yield advantage with the conservation-tillage system.

“Ridge-till often allowed earlier planting,” Reeder says. “However, overall, ridge-till and plow gave the same yields. Economically, ridge-till was better because of lower equipment costs.”

For corn in rotation, no-till and strip-till yields were higher than plowing. Strip-till, a common practice on rotating corn, outperformed subsoiling.

“Corn performed about 5 to 10 bushels per acre better with strip-till compared to subsoiling,” Reeder says. “That’s good. Strip-till is a lower-cost system than subsoiling.”

For soybeans, subsoiling provided higher yields than any other conservation-tillage practice. No-till, the most common practice for soybean growers, yielded an average of 6% higher than plowing.

“Considering a corn-soybean rotation on either drained or undrained soils, continuous no-till would be the best single tillage option,” Reeder says.

Reeder and Brown agree that although a combination of several agricultural production practices provides yield advantages for corn and soybeans, the key to making it work best to the farmer’s advantage is good drainage.

“You can’t afford not to have good drainage," Brown says. "On any poorly drained soil, effective surface and subsurface drainage would be an economic and environmental benefit to the grower.”