Fragipan Breakdown By Ryegrass Could Lead To Higher Yields In Kentucky

 

University of Kentucky College of Agriculture soil scientists are getting promising results from several treatments that appear to be breaking down the fragipan, a cement-like layer common in many soils in Western and Central Kentucky.

 

 

Soil fragipans exist in 2.7 million acres in Kentucky and in 50 million acres in the United States. In Kentucky, the average depth of the fragipan layer in the soil is about 20 to 24 inches. This results in a shallow soil that limits crops’ yield potential due to low water-holding capacity. This is especially true during dry growing seasons or droughts. These same soils are easily saturated with water in the winter, which limits yields on cool-season crops such as wheat.

 

Breaking down the fragipan would increase the soil depth and should significantly boost grain yields in the state, similar to the boost farmers received from implementing no-till production.

 

“Earlier work done by UK soil scientists found that soil erosion caused a loss of 3 to 6 percent of yield potential for every inch of lost topsoil,” said John Grove, UK soil scientist. “Additional subsoil rooting depth has a similar potential to increase yields, but it will depend on seasonal rainfall.”

 

Four years into the research project, Grove and fellow UK soil scientists Lloyd Murdock, Tasios Karathanasis and Chris Matocha have found that annual ryegrass and some chemical combinations appear to break down the fragipan.

 

“Annual ryegrass looks promising in the lab and in the greenhouse at breaking down the fragipan. It is beginning to show promise in the field,” Murdock said.

 

The idea to try ryegrass came from previous research conducted in southern Illinois by a former University of Illinois scientist.

 

“Mike Plumer thought he saw annual ryegrass doing something to fragipan soils in his cover crop research that would increase yields,” Murdock said.

 

In the lab, Karathanasis submersed chunks of fragipan in several different solutions, one of which was a ryegrass extract.

 

“Within two to four weeks we began to see the ryegrass extract break down the fragipan,” he said. “Not only does ryegrass have a deep root system that can penetrate the pan, but it also releases a chemical or chemicals that can help break it.”

 

UK soil scientists have planted annual ryegrass as a cover crop in grain fields followed by either corn or soybeans for the past three growing seasons with the fourth round now in the ground. The first year when annual ryegrass was followed by corn, there was no yield difference.