Kentucky Soil Scientists Discover Ways to Improve Plant Growth


Nearly 3 million acres in Kentucky and 50 million acres across the United States contain a naturally-occurring soil layer called a fragipan. This cemented, silt loam soil found 20 to 24 inches below the surface stops water movement and root growth, which can reduce crop yields.

Dr. Lloyd Murdock, an extension soil specialist and professor with the University of Kentucky College of Food, Agriculture and the Environment, has been studying soils for more than 50 years. He knew the fragipan was a significant issue for Kentucky farmers, so he began a research project five years ago to find a way to dissolve or “remediate” the soil layer.

Dr. Murdock and his research team began by testing hypotheses in the laboratory, then moved to a greenhouse, followed by field research. After testing many plants and compounds, they found that planting annual ryegrass, a popular cover crop and lawn grass, was one of the most promising methods of dissolving the fragipan layer. This is due to a chemical compound found in the roots, as well as the fact that the roots will penetrate the soil deeply. Other compounds and different annual ryegrass varieties are also being studied.

In a three-year trial on the UK Research and Education Center in Princeton, corn and soybeans had an average yield increase of 9.8 percent per year on fragipan soil that had an annual ryegrass cover crop compared to a soil that had no cover crop. Scientific evidence indicates that fragipan breakdown increases with time and the continued use of ryegrass as a cover crop. Dr. Murdock concludes that yields should continue to increase with time, and farmers could see a 25% increase in grain yields on fragipan soils. This production increase could result in $500 million in additional income to Kentucky farmers per year.

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