Carbon Cycling, the key to High Productive Soils and Higher Profits
Coffee County Soil Conservation District is very active in promoting, and are very successful in applying conservation practices to improve soil health. Adam Daugherty, Allen Willmore, the Soil Conservation District Board, and many farmers have come together in unison promoting soil health resulting in over 75 farmers actively practicing long-term no-till and the use of cover crops to regenerate their soils and change the overall soil health. They are mimicking nature with diversity and pumping carbon into the soil to ignite both quantity and quality of soil biology resulting in breaking down freshly produce carbon and improving soil aggregation and nutrient cycling. One farm in particular has been a focus of many soil health meetings, soil health field days, and even the location for NRCS' soil health team to meet and develop our soil health strategy for the state. I know personally that I have been on this farm no less than six times. Robert Henley is agronomist at Security Seed and Chemical and landowner/manager of his farm of 70 acres in Hillsboro, Tennessee in Coffee County. Robert is our 38th Profiles of Soil Health Hero.
Robert is well known in Coffee County in assisting farmers to reach their yield potential in corn and soybeans. Adam Daugherty, NRCS District Conservationist credits Robert and a few other farmers in the county to ask the right questions to motivate thinking and progressing in a carbon-driven agricultural system to transform soils to from somewhat dysfunctional to functional. I first met Robert in February of 2014 at a soil health meeting on his farm. We were touring one of his more productive fields that later in 2014 yielded 315 bushels of corn dryland production in a national corn yield growing contest. Robert, at the time, had some wheat and Austrian winter peas planted for cover crops. We learned from Adam and Robert that the high producing field had been in cattle production for 53 years. It was in predominantly fescue for over 53 years. Unlike many farms that are tilled converting grasses to crop land, Robert no-tilled into the fescue field, so it was never tilled in the last 60 years plus. Robert remarked the day that I interviewed him for this article on October 11, 2017, that the field was left in grass so long because it was thought to be unproductive for corn and soybeans.
Another field that Robert pointed out, on that February of 2014 tour, was a field that was similarly mapped to the high producing field, Hamblen silt loam. This field has had a history of pasturing swine and also was cropped in the 1980s using tillage. Robert told me recently that phosphorus levels are over 400 pounds per acre and potassium are over 600 pounds per acre. So, nutrients are very high. In 1980, Robert reminisced that the field was planted to green beans. They had completed the harvest in wet weather and had severely rutted the field. Robert recalled that they proceeded to work the field up wet. Robert said that the field has not rebounded since that series of events in 1980. On our tour in 2014, the green bean field did not have cover. The following fall, both fields were planted to Austrian winter peas.
The NRCS staff had done significant soil testing and soil health evaluations. Adam Daugherty shared with me that they measured 24" per hour infiltration rate using a 6" single-ring after harvest of corn in 2014. Robert followed with winter cover of Austrian winter peas and during planting of soybeans in 2015, the water infiltration rate was 4" per hour. The question was why. I have seen similar results after a monoculture cover crop of crimson clover in Maury County. Soil biology needs energy to function. Carbon is an energy source. Grass and multi species provide diversity and carbon as energy source. When carbon is not available, soil biology will find it inside and between soil aggregates. The lack of soil structure due to degradation of aggregates in one season showed up in the reduced infiltration rate, but the culprit was platy structure or stratified structure due to soil biology cannibalizing the soil aggregates for energy, thus changing the granular soil structure to platy soil structure.
After the 2015 soybean crop, Robert has been in multi species cover crops consistently. He plants 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, all species planted per acre basis. His infiltration is back in the 20-24" per hour rate.
The green bean field has lagged behind his high yielding field. In corn yields, it is consistently 30 bushels less. In 2016, which was a very dry late summer and fall, the difference was 92 bushels per acre. In 2014, which was an ideal year for corn, the high producing field averaged 283 bushels per acre compared to 226 in the green bean field. Robert looked at the weather each year and the differences in yield. The good yielding field had 198 bushels per acre in 2012, which was a very poor yield due to over 15 days being over 95 degrees. The county average was 130 bushels per acre. Robert said that he needed to inject carbon into his lower yielding field to give insurance for the dryer years. The NRCS and Robert came up with a strategy to rest the lower yielding field from grain production in 2017. They concocted a cocktail mix of sorghum sudangrass, sunn hemp, soybeans, sunflower, buckwheat, sweet clover, iron clad cow peas, proso millet, pearl millet, daikon radish, phacelia, and purple top turnip. The concept is to pump more carbon into the field in the summer growing months to fire up the soil biology in order to increase the productivity.
The summer cover crop cocktail averaged between 15,000 - 20,000 pounds of biomass. Adam Daugherty injected that where they applied some nitrogen, the summer mix exceeded 30,000 pounds of biomass. Robert Henley 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 made 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, left side of picture. but without any cover crops. The results are illustrated by the picture. In 30 days the underwear underneath Robert's high yielding field that had been in cover crops ingested the cotton underwear completely leaving only nylon bands. The no-till field under wear was hardly decomposed almost looking new. The no-till with cover crops literally beat the pants off the no-till only. This suggests that soil biology is picky or have a preference to carbon leaking out of the roots. The no-till field had no decomposition of underwear, but had no structure or platy structure showing the same phenomena as growing only a legume. The soil biology is searching and finding sugar-protein from the soil aggregates. This is fully illustrated also in the lower yielding field that had the massive summer growing mix on it. They also buried underwear under it and found no decomposition of under wear. We know with a terminated winter cover followed by a warm season cover crop mix that soil biology are present. They again showed a preference to sugar-protein leaking from the roots of summer cover crops and did not attempt to break down the less appealing under wear.
Digging and examining soil structure from no-till field and spots without cover showed a similar conclusion. Those areas without cover showed platy structure again crediting soil biology for decomposing glomalin and other important carbon that aggregates soils. The high yielding field with plenty of active carbon from the terminated winter cover mix showed excellent aggregation resulting in excellent yields and water infiltration. The conclusion is we must continuously produce active carbon to improve our soil health. I am convinced that a field without a growing plant is a degrading field.
As I mentioned previously, Robert is proficient at reaching high yields in corn and soybeans, and he advises others to reach high yields. Robert is tweaking the cover crop system to be more productive. He mentioned that his current system is resilient regardless of the season. Robert mentioned assisting farmers with irrigation on their farms only showed increased yields only 20% of the time, one year out of five. He said the reason was poor water infiltration which he measured at 0.1" per hour. The problem was not the lack of water but the soil being dysfunctional and could only infiltrate 0.1". Farmers need to treat the problem which is an infiltration problem not the symptom with adding more water. Robert concluded it is much more profitable to pay up to $50.00 per acre for cover crops than to invest in irrigation system.
Robert and Adam both mentioned that farmers considering using cover crops are too concerned with temperatures at planting. This last spring was wet and cool. They took temperatures in no-till, conventional tillage and cover crops and found 3 degrees differently. However, they have done earlier temperature studies in June and July and found cover crops to be 8-10 degrees cooler than ambient temperatures and conventional tillage and no-till to be as much as 13 -15 degrees warmer than ambient temperatures. Robert and Adam both said they are looking at not planting corn until soil reaches 65 degrees because the cover will provide the benefits needed to achieve higher yields even though the planting date may be somewhat later. They both said that the system with cover crops are so much different from a traditional no-till system that is different from the old traditional conventional tillage system.
Robert had advice to farmers not willing to plant cover crops. He has noticed that corn does better and show better soil aggregation when planted to 2" in depth. He compared a farmer's field that was planted at 2" depth to areas planted at 1 3/4" depth. The corn planted at 2" depth yielded 300 bushels per acre irrigated where the corn planted 1 3/4" depth yielded 280 bushels irrigated. Areas showed differences in aggregation too. Robert is also a believer of sulfur. He thinks it is economic to apply much higher rates of sulfur, as much as 100- 150 lbs. per acre. He also noted that where he sees highest yields in corn the soil copper is high. He is an advocate of placement and timing of nutrient placement. He soil tests by zone and focuses on placement and timing instead of mass balance. He gave example that old school nitrogen (N) fertilization was 1.5 lbs. per bushel of corn production. Robert said with multi applications and timing, he could reduce it to approximately 0.4 lb. N per bushel of corn. He applies N three times on high yielding areas and two applications on rest of farm. He also quit applying side dress N between rows, 15" from corn. He now applies liquid N (32% solution) on both sides of corn at a reduced rate (half what the 15" amount is). He sees less decomposition of cover and the corn is yielding better. Previously at 15" centers the N application looked like a blow torch had been applied to the residue.
Coffee County has been soil testing with Haney test and Phospholipid and Fatty acid (PLFA) sampling for three years. These results are showing high amounts of soil biology over 12,000 ng/g at planting compared to another cover crop farmer at 2,500 ng/g. Robert's field is turning over or consuming high amounts of active carbon. The soil organic matter is 2.5 -3% but the soil health changes are due to the soil aggregation and nutrient cycling resulting from high populations of soil biology and large amounts of active plant biomass being consumed. We do not need to be concerned with levels of soil organic matter. Robert also noted that his cation exchange capacity was 19 melliequivalents per 100 grams of soil which is high. The constant production of carbon is making a difference in his soils.
On his pest management program, Robert has not made any change as of yet, but is seeing less pigweeds and mares tail due to the cover crops. He said he currently uses two sprayings for pigweeds/mares tail where traditionally, farmers would use 3-4 sprayings. He thinks by the 4th to 5th year using cover crops, he could knock out a second spraying of post applied herbicides by using rolling and crimping on cover crops.
Robert compared his average $30.00 per acre investment of cover crops to some nearby farmers paying $50.00 per acre for chicken litter. Robert said the scary part was there was no analysis on the litter. Farmers need to know what they are applying per acre. Robert says every farmer needs to invest in a shovel and examine their fields. Functioning soils are much more profitable than non-functioning soils. Robert believes in rolling and crimping his cover crops except when planting crops with a drill. The drill knocks the cover down at planting in an orderly fashion; if the biomass is at a conducive stage for crimping.
Robert said that farmers growing crops near tree lines could be more efficient by planting grass buffers adjacent to tree lines. Robert has noted 100-bushel difference between corn in the middle of field compared to near tree lines. He said farmers are wasting resources by planting crops near tree lines. Robert is not afraid to get out of the box and break tradition in order to change his soils and his bottom line. Many farmers have and are learning from what Robert is doing on his farm. The take home message is to mimic nature by keeping a plant growing 365/24/7 to increase carbon production (photosynthesis), protect the benefits by no-tilling, and diversify too increase quantity and quality of soil biology to cycle the carbon to improve soil function and improve farm profit.