Killing the Pan One Cover Crop at a Time

Junior Upton is fragipan’s nightmare. In the late 1990s, Upton was dealing with drought and strangled yield across much of his farmland. He planted annual ryegrass following harvest, hoping to gain the conventional benefits of a cover crop and no till system. However, the Illinois grower had no idea he’d just lit the fuse on the destruction of a soil scourge.

The eastern half of the U.S. is plagued by 50 million acres of fragipan soil. Light in color, fragipan often starts at 1’ to 2’ below the surface and roughly averages 2’ to 4’ in thickness. A solid barrier of cemented soil particles that slams the door on water passage and crop roots, fragipan is a yield killer. However, annual ryegrass is showing genuine promise as a battering ram against fragipan, evidenced by yield boosts and sustained success on Upton’s farmland.

Upton, 70, has farmed hills and flats since 1964, and the vast majority of his ground is afflicted with varying degrees of fragipan, hiding roughly 8” below his Hamilton County acreage. The white, chalky layer has been a consistent source of diminished yield, no surprise when grain crops subsist on the top few inches of dirt.

In 1983, following a particularly nasty drought, Upton tore out a fence row and burned the brush pile. He dug a pit to bury the remaining stubborn tree roots, and noted moisture far down in the pit profile. He was frustrated to see moisture at 4’ deep, cut off by the overlying soil barrier. Upton accepted the irony as a bitter pill of farming, but desperately hoped for some means to bust up the fragipan.

In 1998, Upton had a field with a notably wide range of scatter-gun yield. On a stretch of hilly ground planted in corn, Upton could find an area of 125 bu. per acre yield, walk 20’ away, and suddenly stand in a 40 bu. per acre zone. The yield spectrum was maddening and spurred Upton to bring in a back hoe for a round of field surgery. Along with Mike Plumer, a former soil agronomist with the University of Illinois Extension, and several research colleagues, Upton dug 150’ across the field. The peeled layers of soil were plain to see: poor corn with fragipan and good corn without fragipan.

Upton obtained a SARE (Sustainable Agriculture & Research Education) grant to trial no till with a continuous cover crop. Plumer made a most fortuitous recommendation: annual ryegrass. His initial idea was to build soil tilth and organic matter to improve Upton’s soil quality.

“Within a couple years we really started seeing progress. I dug down in February and found ryegrass roots down 2’ on a 2” plant. I was excited and called Mike. In just a few years, we had ryegrass roots down at 72” on 4” plants. That’s when we knew ryegrass was breaking the hardpan,” Upton says.

Fragipan is an acid soil-type and runs a pH of 4.5 to 5.4, but ryegrass doesn’t mind the low pH, Plumer explains. In wet winter conditions, annual ryegrass cracks apart fragipan by opening root channels. “In just the first year of use we saw rooting at 24” to 28”. The second year was 30”. In four years rooting was at 60” to 70”,” Plumer says.

When annual ryegrass roots die, a network of readily available channels is left behind for corn or soybeans. A no till system keeps the channels open as corn and soybean roots push deeper each year. On tough fragipans with annual ryegrass as a cover crop, Plumer documented the root growth inch by inch and watched corn roots descend from 12” to 70” in just four years. Plumer also observed soybeans roots take advantage of annual ryegrass. In normal fragipan, soybean roots often only reach 12” down, but following five years of annual ryegrass, Plumer recorded soybean roots at 36”.

As the roots grow, the yields expand in tandem. “On Junior’s farm, we’ve got some fields 16 years in the making. His corn yields before we started were at a five-year average of 85 bu. per acre, but after six years, he was over 150 bu. per acre. After 10 years, he was over 200 bu. per acre, and it is all documented,” Plumer says.

Plumer also did on-site fertility tests on ryegrass and non-ryegrass ground. “The ryegrass went so deep and picked up phosphorus and potassium. We were doubling and tripling the P and K tests without even making applications,” he notes.

“The key is to be 100% no till,” Upton says. “The ryegrass roots go in during winter when it’s soft and make a highway system. Then it becomes just like the open road you drive every day to your house. As long as a tree doesn’t fall over it, you can travel the road anytime.”

Initially, Upton and Plumer were met with long looks and disbelief. Annual ryegrass to bust apart fragipan? “There were soil scientists telling us there was no way possible this was happening,” Upton says. “After a few years, we had an August field day and dug into corn to show them 4’ roots. It was visible and they all could see it. I never set out to do this at all; it just happened.”

“We had lots of people thinking we were crazy,” Plumer echoes. “We took them to the site and put them in the pit to show them. By 2008, people started getting interested. After the 2012 drought, they really started getting interested.”

The 2012 drought was a dismal benchmark, triggering an anemic 25 bu. per acre corn yield average across Hamilton County. Upton’s whole-farm average was over 80 bu. per acre. However, on his long-term annual ryegrass fields, the difference was massive: 140-150 bu. per acre.

Annual ryegrass doesn’t merely create rooting channels, it literally breaks down the fragipan, Plumer notes. The white cement material dissolves and leaches deeper into the soil. Plumer has recorded 3” of downward movement over a single year. Upton is experiencing legitimate alchemy because some of his fields don’t have much fragipan left and it has moved 30” into the profile, according to Plumer.

Annual ryegrass secretes an enzyme through its roots and can be devastating to soybean cyst nematodes (SCN), Plumer says. When soil warms to 60 F with annual ryegrass present, SCN prematurely hatch prior to soybean planting. Plumer noted a 50% to 90% reduction of SCN in a single year.

Plumer recommends 10-12 lb. of annual ryegrass per acre at planting in the fall, immediately following harvest. In the spring, he kills annual ryegrass at 6” to 8” in height, just before joints set and surface roots proliferate. “The No. 1 ryegrass issue I hear is, ‘I can’t kill it.’ That’s because herbicides aren’t being used correctly,” Plumer says.

“Glyphosate is neutralized by many rural water supplies. Fill the tank with water and put in ammonium sulfate. Then put in an acidifier to take the water to 5.2 pH prior to adding glyphosate. You must use treated water, or face a possible 50% to 60% reduction in efficacy,” he adds.

Annual ryegrass goes dormant below 38 F, and below 35 F, won’t uptake glyphosate for three days even after a warm-up, Plumer explains: “In cold weather, glyphosate must be sprayed in the morning and must stop by 2 p.m. because it takes four hours before sunset to translocate into plants. Otherwise glyphosate will be neutralized overnight.”

Since 2012, Lloyd Murdock, Extension soils specialist with the University of Kentucky, has been part of a research team attempting to break down the mysteries of fragipan. “When I first heard about Junior and Mike’s success with annual ryegrass, I dismissed it because it didn’t make sense,” Murdock admits. “Junior and Mike were ahead of everyone else on this research.”

Based on the Plumer/Upton work, Murdock included annual ryegrass as one of the many plants and materials he tested in laboratory and greenhouse settings. It proved effective in both venues. “We could see it change the fragipan profile in the greenhouse and in Upton’s field on our visit there,” he adds.

Murdock wants to reverse engineer the process. Scientifically, he isn’t 100% certain of the mechanisms involved – but he’s pretty close: “We think it may be a chelating situation where ryegrass chemicals remove the aluminum out of aluminum silicate in the fragipan. Essentially, the silicate is then free and doesn’t have anything to cement it together. Instead of cemented particles bonding, you end up with individual particles that make soil.”

Encased in plastic, Murdock takes fragipan cores and grows annual ryegrass overtop in a greenhouse setting. In the first round of annual ryegrass, changes are minimal. However, in the second and third rounds, the fragipan begins to break down and change color. It continues to change more of the fragipan with each planting.

Murdock has located fields in Kentucky where annual ryegrass has been grown as a cover crop or for cattle feed. When compared with adjacent fragipan fields, Murdock observes an additional 5” to 6” of soil that was formerly fragipan. “We’re gathering evidence right now to say it’s real scientifically,” Murdock explains. “Fragipans in Kentucky, Illinois, or Alabama are all somewhat different. We don’t know how representative these numbers are because nobody has ever done this before. This will be huge if we get scientific confirmation.”

Murdock is ramping up research and has established strip trials in three Kentucky fields. He also is performing chemical compound research in combination with annual ryegrass to accelerate fragipan breakdown. Four chemicals show fragipan promise: potassium chloride, potassium sulfate, sodium nitrate and sodium fluoride. He hopes these compounds, when surface applied, will follow pores provided by annual ryegrass, and travel down through the soil profile with enough concentration to attack underlying fragipan. Murdock is excited about annual ryegrass with a chemical coattail, essentially a one-two punch to fragipan. “Our greenhouse research is strong. It took us awhile to gain confidence beyond the lab, but this looks very right,” he says. “The benefit would be huge for agriculture.”

Murdock will wait until after fall 2017 harvest to make a final determination. If his research passes the final hurdle, he’ll begin work on an Extension publication and lay out the evidence for producers pointing toward the economic boost at stake: “Put economics to what Junior has done and it shows he broke even after four years with $4 corn. From that point forward, he made money, and by year 15, the difference was outstanding. Over a 15-year period, he cleared more than $1,000 per acre on the field than he would have by leaving it alone.”

“If someone told me 25 years ago that annual ryegrass had a remediation effect, I wouldn’t have listened and that was my stance,” Murdocks adds. “I’ve totally changed.”

Back on his Illinois farm, the humble Upton simply advises others to examine his ground. “I was 20 bu. below and now I’m 30 bu. above the county average, but I can’t stand anyone to think I’m bragging. I sure understand if people don’t want to listen to my words, but they can look at my soil,” Upton says. “All I’m doing is pointing toward what’s working on my ground.”

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