Fragipan Remediation

  • Murdock, Lloyd (PI)

Grants and Contracts Details


BACKGROUND The fragipan is a naturally occurring soil horizon that virtually stops water movement and root growth through the soil. Itsf depth averages about 20]24 inches in the soil types in which it occurs. The layer is due to the cementation of the soil particles with a silicate rich amorphous aluminosilicate binding agent. The fragipan is present in about 2.7 million acres of Kentucky soils and about 50 million acres in the U.S. Fragipan soils reduce yields of crops for 2 reasons: 1) limited water holding capacity due to limited soil depth 2) water saturated soil conditions during wet periods. The fragipan itself is a silt loam soil that has been cemented. If the cementation is dissolved, the released soil particles can begin functioning as a productive soil again. The goal of this project is to try to dissolve the cementation and make a deeper soil that will hold more water for summer growing crops and reduce waterlogging in the winter which would make the soil better suited for winter crops and better support trafficking at this time of the year. The approach to investigation of a remedy to the fragipan has three phases. „h Laboratory research and evaluation „h Greenhouse research and evaluation „h Field research and evaluation RESULTS The research on the fragipan by the research team includes testing many plants, compounds and combinations. There are two plants, potentially 4 compounds have been found to be effective in breaking apart the fragipan. They are annual ryegrass, festulolium, potassium chloride, potassium sulfate, sodium fluoride, and sodium nitrate. Leonardite humate shows some possibilities. Field research in Illinois, Indiana and Kentucky offers additional support for the effectiveness of ryegrass. Annual ryegrass has been chosen as the central focus of the greenhouse and field research due its notable advantages and the compelling proof of its effectiveness. Annual ryegrass roots apparently contain exudates that have a degrading effect on the fragipan. The deep root penetration also increases soil porosity and may facilitate the leaching of the 4 or 5 other effective compounds down to the fragipan. The 4 chemical compounds are being tested in the field and in the greenhouse. Festulolium is showing excellent promise in the greenhouse and is entering field testing. Leonardite humate shows promise in the greenhouse and is in field testing. Through research findings in the laboratory, greenhouse and the field, we have gained enough confidence in the ryegrass treatment as a fragipan remedy and its yield increase potential, that we have begun cooperating with a few farmers across the state to establish trials. When annual ryegrass was grown 6 times in a rotation with soybeans in the greenhouse, the depth of the newly formed productive soil increased about 7 inches. We have also found 3 fields in Kentucky, 2 in Indiana and 1 in Illinois that had a history of at least 5 years of annual ryegrass over a 10 year period. The annual ryegrass increased soil depth by as much as 14 inches and as little as 3 inches. We are also finding lower bulk density and increased porosity as well as an enrichment in some organic compounds in the fragipan horizons undergoing degradation in the greenhouse where ryegrass is present when compared to the control. We are also finding compounds which we suspect that are compounds which are exudates released from the ryegrass roots which induce the fragipan degradation. At present time, we are trying to scientifically verify and identify the exudates. It will greatly aid in this effort and may lead us to a quicker and more effective method to remediate the fragipan. The yield comparisons that we presently have from field trials with and without annual ryegrass on fragipan soils are of rather short duration (3 to 6 years). It appears that little or no yield gain is common in the first two years. Yield gains after this become more consistent and significant. In 2018, yield comparisons from six field trials were harvested. The yield gains found when using annual ryegrass as a cover crop ranged from 3.1% to 13.0% with an average of 6.4%. Five of the sites had an annual ryegrass cover crop for three years and one for six years. The only long term data we have shows an average yearly increase of corn grown after an annual ryegrass cover crop on a fragipan soil in southern Illinois is 3.7 bushels per acre per year over a 15 year period compared to the average corn yields for that county. This is not a scientific trial but indirect evidence on what might happen with time. The increase is accumulative resulting in an increase of 55 bushels per acre the 15th year. This results in an increased return of $1,228/ac over those 15 years for using annual ryegrass as a cover crop. This is calculated using $4/bu for corn and an expense of $36.50/ac for planting and killing the cover crop. For 1,000 acres the increased return would be $1,228,000 over those 15 years. With these limited results, it appears that it might be possible to increase yields of corn and soybeans by 25% on the fragipan soils by using an annual ryegrass cover crop over a number of years. We also expect to improve the yields of wheat. A 25% increase would result in $500,000,000 in increased returns to Kentucky producers per year or $5,000,000,000 over a 10 year period on the 1.5 million acres of cropable fragipan soils in Kentucky. There is 2.7 million acres of total fragipan soils in Kentucky. Kentucky has only a small portion of the fragipan soils in the U.S. There is about 50 million acres of fragipan soils in the U.S. 2020 PLANS 1. Begin field trials of festulolium in Kentucky and Indiana. 2. Begin drilling trial in Todd where 6” holes are drilled through a shallow fragipan on a grid pattern to test its’ effectiveness in remediating the fragipan. 3. Hold a field day in Hickman County Kentucky on the Jerry Peery farm concerning the use of annual ryegrass to remediate the fragipan in March 2020. 4. Publish the first ever publication on the remediation of the fragipan. An Extension type of publication. 5. Continue field testing of NaNO3, KNO3, KCl, CaNO3 and humates. 6. Continue annual ryegrass field testing.
Effective start/end date9/1/1912/31/20


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