Soil Health Changes in Three Years in Haywood County and Results of Rainfall Simulator at UT Experiment Station, Milan Tennessee
by Mike Hubbs, TACD Soil Health Specialist
On March 23, 2017, I had the opportunity to visit Bill Parker out on the Solomon Farm in Haywood County. This has been a farm that Bill has farmed the last three years. I had the opportunity to previously visit the farm in October of 2015. The two previous years of cover consisted of rye and crimson clover. This year was a five-way mix aerial seeded in early October. The stand was decent despite the drought, last Fall. Also, joining me on the visit were two farmers from Haywood County, a farmer from Lauderdale County, a Farmers Cooperative employee working Tipton and Lauderdale Counties, and NRCS employees from Brownsville, Tennessee, Joshua Choate, District Conservationist, and Melissa Rodriguez, Soil Conservationist. First of all, it was amazing the surface changes in the soil noted while digging. The soil was much fluffier or had better tilth. The structure had changed from a platy structure to much more granular and sub-angular structure. We like to see soil structure with the somewhat rounded shapes similar to marbles in a glass. They form soil-voids or pore space that leads to porosity. Porosity provides space for air and water movement most notably improved infiltration rates. We have noted anecdotal evidences for years with cover crops and no-till. We see it when comparing samples with the rainfall simulator. When compared to long-term no-till and vertical tillage and conventional tillage, samples with two to three years of history of cover crops and no-till perform better under rainfall simulator. They infiltrate better due to more cover and better aggregation due to more active soil biology. There is less run-off and erosion. Water is more efficiently infiltrated and utilized by plant roots. We also observed many earth worms in every shovel full of soil. Bill remarked that he had not seen many earthworms in the past. Earthworms is a macro biology indicator that soil health is improving. Earthworms, like other soil organisms, feed off other soil biology such as bacteria, fungi, nematodes, etc. as well as soil organic material from crop residues and cover crops. Lack of tillage is very favorable to earthworms. As time persists with no-till and cover crops, earthworms and other soil biology will increase. These organisms increase nutrient cycling, aggregation of soil, and movement of nutrients and soil organic matter both upward and downward. Earthworms are nature's tillers. Another indicator that was very observable was the strong earthy smell when digging. The sweet soil aroma was much less in 2015 compared to now. Earthy smell is from geosmin, an organic compound produced from actinomycetes, a colony growing bacteria. As soil is undisturbed and organic matter increases, soil earthy smell increases.
I want to summarize some of the discussions with the group I met with on March 23. There was one farmer in the group already farming with cover crops and no-till. Two other producers do not no-till or use covers on cotton but will no-till with corn and beans, but have not used cover crops often. They have used wheat on occaision. Here are some of the questions and responses. Why use multi species and not one species, such as wheat? Although there good data on one species such as cereal rye at Auburn University and other locations, multi species, especially more than one species, aggregate the soil better. We have run several on- farm tests, and see better aggregation and soil structure with multi species. When using rainfall simulator, more species do a better job. Two species better than one, and one better than none. Agronomy text books and field guides always stressed crop rotations to break disease cycles, insect, and weed cycles and increase yields. Multi species add diversity. Many on-farm soil tests showing nutrient available, water extractable carbon (food source for soil microbiology), carbon and nitrogen ratio (quality of carbon), and soil respiration (soil life) are more prevalent in multi species cover crops. UT is now showing some yield data. The reason for lack of research data is the complexity of multi variables and time. NRCS has promoted multi species for approximately four years. It takes that much time to receive results from experiments. We do know from data and experiences, when you do not till, soil improves. We do know that if you add cover crops, carbon will increase in soil. In time, multi species and no-till will improve soil and productivity. One last question that a farmer asked. He asked that the X farm had three years of no-till and cover crops and had soil organic matter (SOM) at approximately 2 %. He said he had Y farm that had not been farmed without cover crops and no-till, and soil tests showed similar SOM levels. I know the X farm at a history of 20 years of tillage and cotton history and soil removal from construction of terraces. The beginning amounts SOM were low. I do not know the levels. Also, I do not know the entire history of Farm Y. I don't think one can draw conclusions from comparing soil tests without having all of the factors available. The current soil from Farm X show remarkable changes and SOM will climb eventually. It is a slower indicator when compared the water extractable carbon or water infiltration. Again, experiences show us if you no-till and use multi species of cover crops, SOM levels will increase. I have seen it on many farms. It takes consistency, patience, and time.
Also last week, March 21, 2017, Matthew Denton, NRCS, Jackson, Tennessee and Dr. Forbes Walker, University of Tennessee, Knoxville, Tennessee provided training to UT Extension employees, NRCS, and some students from UT Martin. Matthew and Forbes showed rainfall simulator results with samples taken from University of Tennessee's plots at Milan, Tennessee. Matthew's and Forbes first observation were between cover crops drilled and broadcast, see picture on left. Last fall was uncharacteristically dry. The better moisture from drilled cover crops showed a thicker stand. Moisture is key for establishment in the fall. The five trays used were from five treatments, no-till only, wheat only, cereal rye and crimson clover, five-way mix consisting of cereal rye, wheat, crimson clover, daikon radish, and purple top turnip, and 2-way mix with cereal rye and vetch. Rainfall simulator were demonstrated multiple times totaling 3" of water. Matthew reported that all trays had good structure due to long-term no-till. Normally we run tillage plots compared to no-till and cover crops. Matthew stated these trays represented soils that were improving and of good quality. Matthew also reported that five-way mix performed best. Other cover crops did better than control plots (no-till only). The two-species did better than wheat only. Also, UT is reporting in fourth year a ten-bushel increase in soybeans probably due to more moisture. Pictures indicate what Matthew said. See from left no-till only, wheat as cover, cereal rye and crimson clover, five-way mix, and cereal rye and hairy vetch. Note the better infiltration of five-way mix fourth from left, the jars in back are showing infiltration. Note below, little or no run-off in front jars (showing run-off) on five-way mix, fourth from left.
Also on April 5, 2017, Tipton and Lauderdale Counties Soil Conservation Districts are having a soil health field day. The location is Parker Farms' Shop at 5495 Durhamville Road, Ripley, Tennessee 38063. There will be field demonstrations and rainfall simulator.