Back in the late 1970s, the U.S. was in the midst of an OPEC oil embargo and subsequent gasoline shortages, complete with long lines at the pump and in some cases alternate days in which motorists could buy fuel.

That scenario was the backdrop for a series of U.S. Department of energy-sponsored tests to determine how much residue farmers could take off the soil to use for fuel.

While most studies came and went, generating valuable and useful tillage information, a study at the PeeDee Agriculture Research and Extension Center near Florence, S.C., remains today and sheds some interesting light on the benefits, and lack thereof in some cases, of long-term no-till farming.

Combined with a much more current series of tests to map the cotton plant genome, the old and the new may combine to unlock some of the secrets of water management in cotton that have challenged cotton farmers for centuries.

USDA Agronomist Phil Bauer, who has spent most of his career at the South Carolina facility, showed samples of soil that has been no-tilled since 1978, compared to soil from continuous conventional-tillage for the same period of time.

While the visual results were easy enough to see, Bauer cautioned that these differences didn’t always result in higher crop yields.

Since 1978, researchers at the PeeDee Station have monitored the test fields, which have been in either conservation-tillage or conventional-tillage for over 30 years.

For the first three years of the study, corn was planted each year on the two test sites. From 1982 until 1986, the fields were in a corn, wheat and soybean rotation.

In 1987, there was a severe drought and nothing was planted on the test site and for the next nine years there was a corn, wheat and cotton rotation there, followed by five years of corn, wheat and soybeans.

From 2003 until 2010, researchers switched to corn, rye and soybeans, followed by corn and cotton last year.

In conventional-tillage plots, fields were disked twice, then smoothed with a ‘do-all’ and sub-soiled and planted. Conservation-tillage plots were sub-soiled and planted.

After 30-plus years, samples from the conservation tillage fields showed significant organic matter in the top three inches of the soil — clear enough for growers to plainly see during Bauer’s presentation at the recent field day.

Soil from the conventional-tillage plots was just a clearly devoid of organic matter — exactly what you would expect, Bauer says.

“Corn has been in these tests in most of the years of the project and some years yields were higher in conventional and in other years higher in conservation-tillage plots. Over the first 30 years of the test, he says, overall corn yields were virtually the same.

Soybeans were less frequently in the tests, but were planted off and on throughout the first 30 years of the ongoing project. Again, over all the years of soybeans in the two tillage system, the total yield was very much the same — right around 30 bushels per acre, Bauer adds.