Coffee County Soil Conservation District
Robert Henley, an agronomist at Security Seed and Chemical, owns and operates his 70-acre farm in Coffee County, Tennessee, with nature in mind. He hosts soil health field days and NRCS’ soil health team meetings on his operation and has been involved in developing a soil health strategy for the state.
Robert is well known in Coffee County for helping farmers meet their yield potential in corn and soybeans. Adam Daugherty, NRCS district conservationist, credits Robert and a few other farmers in the county for motivating their neighbors to think progressively about carbon-driven agricultural systems. In 2014, Robert’s dry land corn crop yielded 315 bushels per acre at the same time he was growing wheat and Austrian winter pea cover crops. This field, having been predominantly fescue and in cattle production for 53 years, has not been tilled for more than 60 years.
The local NRCS has done significant soil testing and soil health evaluations on Robert’s farm. When Robert was applying nitrogen the “old school” way, he was purchasing 1.5 lbs. per bushel of corn produced. Now with cover crops and better timing, he applies just 0.4 lb. per bushel of corn and has quit applying side dress N between rows.
Since 2015, Robert has been using multi-species cover crops consistently. His current mixture is: 15 lbs. cereal rye, 10 lbs. winter oats, 15 lbs. triticale, 5 lbs. crimson clover, 4 lbs. hairy vetch, 10 lbs. Austrian winter peas, and 1.5 lbs. of diakon radishes per acre. His water infiltration rates are back in the 20-24″ per hour range.
This summer cover-crop cocktail averages between 15,000 – 20,000 pounds of biomass. Adam said that where they applied some nitrogen, the summer mix exceeded 30,000 pounds of biomass. Robert said they were trying to emulate the high yielding field that had over 50 years of fescue by producing a large quantity of plant biomass (carbon) in one growing season.
In order to demonstrate the results of soil health practices on soil biology, the NRCS staff buried some cotton underwear in the high yielding field and also in an adjacent field next door to Robert. That field had been in long-term no-till, but without any cover crops. The results are illustrated in the picture at right.
In 30 days, the underwear underneath Robert’s high yielding field that had been in cover crops ingested the cotton underwear, leaving only nylon bands. The no-till field underwear was not decomposed at all. The no-till field with cover crops literally beat the pants off the no-till only field when it came to decomposition rate. This suggests that soil microorganisms are picky and may have a preference for carbon leaking out of roots.
The men buried another pair of underwear in an adjacent, lower yielding field that had a summer mix growing (pictured below). This underwear showed no decomposition, which suggests that the soil microorganisms present had a preference for the sugar-protein leaking from the roots of summer cover crops and did not attempt to break down the less appealing underwear.
Digging and examining soil structure from a no-till field without covers showed a similar conclusion. Those areas without cover showed a platy structure, while the high yielding field with plenty of active carbon from the terminated winter cover mix showed excellent soil aggregation, yields, and water infiltration.
Robert is tweaking his cover crop system to be more productive and often works with other farmers to determine ways to increase yields. Recently, he discovered that using irrigation in his area only increased yields 20% of the time, one year out of five. This is because water infiltration rates in the county are so poor (just 0.1″ per hour on average), he said. “It is much more profitable to pay up to $50 per acre for cover crops, than to invest in irrigation system,” Robert concluded.
Robert says that farmers considering using cover crops are too concerned about planting them at the right temperatures. Right now, he’s experimenting with waiting to plant corn until the soil reaches 65 degrees. “The cover will provide the benefits needed to achieve higher yields even though the planting date may be somewhat later,” he says. “The system with cover crops is so much different from a traditional no-till system and even more different from the old traditional conventional tillage system.”
Robert encourages farmers to try cover crops by providing evidence of their effectiveness. When planted at 2″ depth, for instance, corn yields are 300 bushels per acre irrigated, whereas the corn planted at the 1 3/4″ depth yielded 280 bushels. Cover crops allow for that deeper planting, he says.