MUNCIE, Ind. — Data from 50 years of research on continuous no-till plots show significantly higher crop yields than in till plots, said Alan Sundermeier, associate professor at The Ohio State University.

No-till methods, when combined with cover crops and controlled traffic of heavy equipment, produce the least compaction of soil over the long term, he explained last week to a crowd of 50 farmers during a Purdue University extension workshop at the Delaware County Fairgrounds.

Despite the overwhelming evidence for this approach, Sundermeier said some farmers are reluctant to embrace no-till and cover crops, because of short-term economics.

"It’s tough when you’re renting ground at a high price, and you’re trying to push as many bushels out as you can. Tillage is releasing organic matter, but it’s short-term gain for long-term loss," he said in response to a farmer’s question.

Sundermeier explained reducing tillage allows the soil to retain organic matter, which stores or "sequesters" carbon. "We’re going to get regulated if we’re not careful. The challenge is how to get landowners to demand better management practices," he explained.

He presented findings based on a 50-year continuous no-till and plow-till study by the Ohio Agricultural Research and Development Center. The center conducts test plots in all four corners of its state.

Continuous corn showed the widest margin, with a yield of 133.5 bushels per acre in no-till plots versus 91.3 in plow-till. Other rotations, such as corn and soybeans, showed similar but less drastic results.

Total carbon retention increased by 1 percent in the top 4 inches of soil with no-till, compared to plow tillage. However, corn-soybean rotations showed the least improvement in carbon retention, while corn-oats-hay rotations showed the maximum at 3.5 percent carbon – an increase of 1.5 percent.

"This took up to 50 years. It doesn’t work overnight. Adding other residue – in this case, oats and hay – plus no-till makes a difference," Sundermeier said.

No-till plots also showed gains in both active carbon and total phosphorus.

Sundermeier said newer soil testing methods are being developed to measure other aspects of soil health. "The newer soil testing will measure things besides chemicals. It will measure organic material. A higher percentage of active carbon shows the soil is more alive. If we do not disturb the soil, we are allowing microbes and earthworms to work the earth," he added.

Microbial biomass after 40 years of no-till practices showed steady gains especially in the top 3 inches of soil, but also at other soil depths. At the surface, the microbial biomass was measured at lower than 150 parts per million (ppm), contrasted with 300 ppm after 40 years of no-till. At 9-12 inches of soil depth, the microbial biomass increased from about 40 ppm to about 120.

The survey conclusively showed that adding cover crops to the mix with no-till resulted in greater yields, Sundermeier said, as evidenced by a "dramatic yield difference" during the drought of 2012. Conversely, because of their moisture-holding properties, cover crops also help protect against flooding.

The cover crops increase moisture-holding properties of soil by reducing evaporation and building soil organic matter. They can also combat soil compaction because their roots expand the soil, creating space for water and air. The study showed compaction was reduced by 40 percent in a radish field when compared with an open field.

Contributing to soil compaction is the increasing weight of tractors and other equipment, Sundermeier said. Tire ruts can compact soil by 50 percent. Therefore, controlling traffic on fields is an important component to improving soil health.

For example, a 2,000-bushel grain cart at 30 tons per axle can cause compaction down to 34 inches deep. A field study showed aerial images with black ruts for each tire. Other factors in compaction are rain and gravity. Farmers have control only over their use of equipment, Sundermeier pointed out.

The ideal soil composition should include 25 percent water, 25 percent air, 45 percent inorganic matter and 5 percent organic matter.

In battling compaction, the traditional response is to use a subsoiler, which can produce an immediate change in soil structure down to 18 inches deep and increase water infiltration, but also leaves soil susceptible to compaction later, Sundermeier explained.

Cover crops, on the other hand, produce a slow change in soil structure 3 feet deep or deeper, and increase infiltration over time. They can also protect from erosion, add nutrients and organic matter and fit into a continuous no-till system.

Soil resistance to compaction is greatest when continuous no-till is combined with controlled traffic of heavy equipment and cover crops, he concluded. The soil’s ability to absorb water is directly related to potential ponding and flooding. It also affects rainwater runoff, but studies show runoff is not addressed by no-till practices alone.

The soil’s water infiltration rate in an hour was best in no-tillage with 80 percent cover crop, but worst in no-tillage with a bare surface. Residue cover prevents soil crusts, Sundermeier explained.

Further, field tests reveal in a conventional-till field, sediment runoff is an issue, while clear runoff results from the no-till field without cover. Cover crops add additional protection from runoff.

Purdue extension of Delaware County conducts two programs each year on soil health, in partnership with the USDA Natural Resources Conservation Service and the Delaware County Soil and Water Conservation District. The next program will be this fall. "There’s a lot of interest in this topic. We had 120 participants last fall. The timing now isn’t as good with farmers getting ready to plant," said Michael O’Donnell, extension educator with Delaware County.

"The first few programs were more generic information, but we found that few people are experienced in this area. Now we are offering practical, on-the-ground help, seeding methods and setting up planters. This is practical information."

For more information, he said farmers can check the website of the Conservation Cropping Systems Initiative at www.ccsin.iaswcd.org