In an age when many universities are sweeping soil science under the rug for budgetary reasons, the UK College of Agriculture is dedicated to exploring soil’s diverse ecosystem for the good of farmers and nonfarmers alike.
Soil is at the base of the ecosystem services pyramid, which sustains all life on Earth. Without soils, there would be no food, no clean water, fewer antibiotics, not even a breathable atmosphere.
“Soils are a thin veneer, but they are that interface between what we do on top of them and what we expect to grow out of them. So it’s critical to maintain the quality of that resource,” said John Grove, a field scientist in the College of Agriculture whose research emphasis is soil fertility and plant nutrition.
Because of soil’s importance and diversity, a number of researchers from different disciplines in the College are concentrating their efforts on understanding soil physics, biology, chemistry, and management. And though Kentucky is their laboratory, their work encompasses and could conceivably affect the rest of the country and vast areas of the globe.
A Delicate Balancing Act
Erosion and runoff are big problems, particularly in a state like Kentucky with its sloping fields, but it’s noteworthy that Kentucky leads the nation in the percentage of cropland acres on which farmers practice no-tillage as an erosion control measure.
Lloyd Murdock, extension soil specialist at the UK Research and Education Center in Princeton, is an expert in no-tillage, a method where corn or soybeans are planted directly into the residue left from a previous crop rather than into a tilled field. The technique is startling in its capacity to hold the soil and improve its structure. Murdock refers back to a 1985 UK trial to measure soil loss.
“It took 20 years to lose an inch of soil where they tilled,” he said. “Any one year, 1/20th of an inch is nothing. But over a period of several decades, it’s huge. Then they measured the no-till loss rate. It took 1,000 years to lose an inch of soil.”
Kentucky farmer Harry Young was among the first in the nation to practice no-tillage on a commercial basis. His son John continues the practice on the 4,000 acres he farms in Christian County. After decades of using the method, John Young has seen an improvement in soil structure.
“There is a higher percentage of organic matter over time from no-till,” he said. “It’s also not as loose when you drive over it after a rain.”
“When you take a handful of no-tilled soil that has built up over years, you’ll see a granular structure, like cookie crumbs,” Murdock said. “They’re stuck together with organic matter―waxes, resins, glues, and fungi growing in there―so you can’t deform it nearly as easily. A soil that’s been tilled, you can take it in your hand and mold it.”
The compaction of tilled soil not only restricts root growth, it inhibits the uptake of nutrients including nitrogen, phosphorous, and potassium that are essential to a plant’s development. Excess amounts of phosphorous and nitrogen can pose serious risks to the environment.
But it goes beyond that. From a farmer’s perspective, lost fertilizer is lost profit, according to Greg Schwab, extension soil management specialist. That’s why he’s working on a number of projects designed to manage fertilizer use more productively and efficiently. Schwab also works closely with Tim Stombaugh, associate extension professor in the Department of Biosystems and Agricultural Engineering, on projects involving precision agriculture. Using GPS and infrared technology, the two are testing a system to control nitrogen input by reading the color of the crop, the idea being that nitrogen-deficient crops are a different color than well-nourished ones.
Biosystems and Agricultural Engineering Chairman Scott Shearer has done his own research in the field of GPS-guided fertilizer spreaders, sprayers, and planters, often working with Shelby County farmer Mike Ellis of Worth and Dee Ellis Farms. Ellis and his brothers Jim and Bob are partners in the farm, growing corn and soybeans. They’ve adopted a number of soil management practices over the years, including soil sampling, no-tillage, and precision agriculture.
Soil testing and UK’s research give the Ellises a pretty good idea where and how much nitrogen, potash, and phosphate is needed in their fields. Armed with those tools, their GPS-guided spreader and side-dress nitrogen applicator automatically apply the correct amount of fertilizer while avoiding non-agronomic areas such as grass waterways and fence lines.
“We have to believe if we do what UK research shows profitable, then the yields are going to increase in the areas that need the fertilizer,” Mike Ellis said. And in fact, the data are showing that’s the case. The Ellises’ corn yields are trending upward, and they can now compete fairly well with Iowa’s five-year average soybean yield.
The Next Frontier. . .
For David McNear, assistant professor in plant and soil sciences, the next frontier is the rhizosphere, the area around the root zone of plants.
Plant roots exude carbohydrates, sugars, proteins, and organic acids into the soil. Different plants exude different compounds, affecting soil microbes differently. To McNear, this is one of the critical interfaces in the system.
“The microbes drive the carbon and nitrogen cycles, global climate change. Those are big things,” he said.
He and fellow assistant professor and grassland ecologist Rebecca McCulley are currently collaborating with soil microbiologists at the University of Colorado to explore how the compounds released from plant roots impact the soil environment. Their study focuses on endophyte-infested tall fescue.
Crop scientists have worked diligently to genetically manipulate the fungus that lives in tall fescue, attempting to keep the benefits it provides to the plant while losing its toxicity to livestock. But changing the physiology of the plant could change the composition of the compounds the roots release. He and McCulley are investigating if the change in the plant could change the microbial populations in the soil, the very things that drive carbon and nitrogen cycling in the 15 million acres of tall fescue grassland in the southeastern United States.
Manage Soil, Manage Climate
Good soil management reaches beyond food and fiber production to one of the pressing topics of the day—global climate change. Soil holds twice as much carbon as vegetation and the atmosphere combined, with the potential to hold even more.
“This idea that soil can be used to remove carbon from the atmosphere is a concept that’s pretty important, because it’s a fairly inexpensive approach to carbon sequestration,” said Paul Bertsch, professor in Plant and Soil Sciences who is president of the Soil Science Society of America and chairman of the U.S. National Committee for Soil Science at the National Academy of Sciences.
Traditional agricultural practices such as plowing and clear-cutting forests have depleted between half and three-quarters of the soil carbon that was present in North America before European settlement.
“One of the exciting things is the potential to enhance soil carbon sequestration above what the equilibrium level was pre-European arrival on this continent by improving management strategies or finding new ways to control the amount and quality of carbon partitioned to the below-ground parts of the plant. Some people believe this is quite possible,” Bertsch said.
It’s a question that many scientists at UK are exploring through research that extends beyond Kentucky farms to around the globe.
“This whole emphasis on the global carbon cycle is an airshed that spans the globe. We’re all connected,” McNear said. “What we do here will have an influence locally and globally."