Persistence and Consistency of No-till and Cover Crops Change Soil Health
Jason Birdsong from Giles County, Tennessee is our 29th in the series of Profiles of Soil Health Heroes. Jason is a fourth-generation farmer. He said that he has literally been farming his entire life. I had the privilege to visit Jason on January 12, 2017, along with NRCS District Conservationist, Rusty Walker, Pulaski, Tennessee. Jason farms corn, wheat, and soybeans. His farming operation is approximately 750 acres. His soils consist of Armour Silt Loam and bottom land soils, Lanton and Roellen. Lanton and Roellen are poorly drained soils.
He plants his soybeans in 19" rows, his corn on 30 " rows, and drills his wheat. He plants his soybeans at 140,000 plants per acre and his corn at 28,500 plants per acre. He works closely with the local NRCS, Giles County Soil Conservation District, and his local University of Tennessee Extension Service. He has conducted experiments with Extension Service on his farm. He is enthusiastic and determined to find this best method and wants to share his results with others. Some of his local findings are the following: soybeans yielded 3.5 bushels more per acre when following a 5-way mix compared to cereal rye alone. They split the field in half with same soil types and planted half in cereal rye and other half in a 5-way mix. In another experiment, Jason used an inoculant for soybeans on his bottom land soils, and showed consistently 3 bushels per acre increase compared to not using an inoculant. On his hill ground, he conducted the same experiment and showed only 1/2-bushel increase per acre using the inoculant. All work on his farm is unpublished.
Jason manages his nutrients and soil pH by grid sampling in 2 acre grids. He formerly applied nutrients based on general removal rates from grains. Now he applies only what is needed by grids and soil test analysis. He is currently applying nutrients using variable rates adjusted by the more detailed soil sampling. He said they have saved thousands of dollars by variable rate application. He has also added variable rate lime application to maintain his pH along the variable terrain of his farm.
Jason said that his family began experimenting with no-till in the 1970s. With the challenges of getting a good stand, and lack of chemistry of herbicides to control weeds, they practiced rotational tillage. With better herbicides and better technology, he has been in continuous no-till since 2010. In 2010, he researched and read and heard other testimonies on soil health improvements by using cover crops with no-till. He had experienced in the past the hard soils using straight no-till and decided to always use some type of cover crop in his management system.
He began using wheat as a cover crop in 2010. Jason continued using wheat as a cover crop in 2011. In 2012, he changed to cereal rye and tillage radishes. He began to see changes in his soil, especially around the planting zone at 2" in depth. The soil structure was better, and he could achieve a stand with less down pressure on his planter. He said that since 2012, he could back off on any down pressure. He also pulled off the spike wheels. He uses a seed firmer and row cleaners with little or no pressure. Row cleaners are only used when planting double cropped soybeans after wheat.
In 2013, He added wheat with cereal rye and tillage radishes. In 2014, he quit using wheat as a cover crop due to it being a host for pests when rotating back to wheat for grain. He used only cereal rye and tillage radishes. In 2015, he went with multi species. He planted black oats, crimson clover, purple top turnips, cereal rye, sunn hemp, and tillage radishes. In the fall of 2016, he planted the same mix with the exception of substituting kale instead of turnips. He also dropped cereal rye from the mix.
First of all, his current mix of cover crops is providing diversity in vegetation which in turn provides diversity to the soil biology. As plants grow during the fall, winter, and early spring, organic acids are exuded from roots. Also, sugars, proteins, and amino acids are exuded from roots. This helps in aggregation of soil particles. Soil particles, sand, silt, and clay are bundled into larger granules and or cubes called aggregates. The way these are placed is called soil structure. Cover crops build soil structure. We want a crumbly soil with the angled blocks of aggregates which provide porosity in the soil. Soils that are tilled with no addition of cover crops have horizontal plates or no structure. This lack of structure or horizontal plates impedes water infiltration. Cover crops along with reducing disturbances (tillage) allow for soils to have good porosity and infiltrate much more water in inches per hour.
Cover crops such as oats and rye also provide allelopathic properties, which is a natural herbicide that inhibits small weed seedlings from germinating. The heavy grass covers also provide a choking out effect to weeds. Weed suppression is a major benefit of cover crops. When tilling, one also continuously bring up more weed seeds. So, no-till with cover crops with diversity can ease weed pressures, especially following University of Tennessee's weed management program in corn, wheat, and soybeans along with continuous use of cover crops.
Jason adding crimson clover to his mix provides nitrogen through symbiotic relationship with bacteria and legumes to fix nitrogen from the atmosphere. Adding a brassica such as a turnip or kale provides a deep-rooted tap root that loosens the soil and brings up nutrients from the subsoil. Nutrient cycling and soil aggregation have been enhanced with Jason's cover crop mix.
Sunn hemp is a warm season cover crop where the rest of the mix is cool season cover crops. By planting a warm season cover crop in early September, one receives aggressive growth in early fall. Sunn hemp is also a legume, so nodulation occurs in fall before winter kill. Nitrogen is taken up by the other species and cycled to the following growing season.
Jason testified that he saw a bump in yields the first year using a cover crop. He was only using wheat as a cover crop. This could have caused an imbalance of nitrogen due to high carbon to nitrogen ratio and tied up some nitrogen. Farmers need to assure there is enough nitrogen when beginning to use covers, especially grasses. The second year he saw a slight decrease in yields. Since year three, he has seen steady increases in yield. I also believe the use of more multi species have contributed to that increase. He has a good carbon to nitrogen ratio in his cover crop mixes. Usually a 28 to 30:1 ratio is sufficient when providing a mixture of cover crops. Farmers need to contact their local NRCS office to develop a mixture with proper carbon to nitrogen ratio. Grasses have higher carbon than legumes and brassicas. The key to improving soil health is increasing soil carbon or soil organic matter (SOM). Soil carbon is 58 % of soil organic matter and the terms are used interchangeably. Increased SOM equals improved soil health due to the many soil indicators that are improved with increased SOM.
I asked Jason why he began to use cover crops and no-till. Jason has two major soil types, Armour silt loam which is an upland soil with natural good drainage. Then he has bottom land soils, Lanton and Roellan, that have higher clay content and have slower drainage when wet. Jason said that the two benefits he wanted the most were better water infiltration and better drainage. Both soil types are infiltrating better, and the bottom land soil is currently not puddling when rains are persistent. I noted the day that I was there, January 12 that there was no standing water. Other fields adjacent to the farm had similar soil types and had standing water. As SOM has increased, the improved soil structure is infiltrating and percolating water much better.
Jason said that a third benefit was much better planting of his cash crop. The soil is much crumblier. I already talked about weed suppression. That is a fourth benefit. Jason said that Palmer Pigweed and mares tail have reduced since using covers. A fifth benefit is more stable nutrient storage. Jason said his soils are naturally high in phosphorus, but now potassium (K) is much more stable. He applies less K. With the higher SOM, there is less demand for lime which is his sixth benefit. Three years ago, he applied 300 tons of lime on 750 acres. Three years later soil test called for only 160 tons. The soil has a higher Cation Exchange Capacity (CEC). Higher CEC buffers the soil or protects it from major shifts in pH. Also by fine tuning his soil tests using grids, he can apply lime by variable rate which also is being more efficient.
A seventh benefit is savings from less applications of foliar fungicides. He has not used foliar fungicides in 2106 on corn or beans. He did use foliar fungicide as preventive use only in 2015. He does use fungicide treated seeds but no foliar spraying during crop growth. He speculates that with no soil splash, there are less diseases. Covers and no-till protect the soil from soil splash. His eighth benefit is soil compaction which is no longer a factor. He said in the past with no-till, alone, he would use a ripper to loosen the soil. He noticed immediate results but then the soil voids would fill in. With covers, the soil voids are maintained. He says farmers need to let the roots work the soil along with the earthworms. No tillage is needed.
Jason went on to say that a ninth benefit is the soil structure has changed to that of cube-like blocks of soil that allow water and air movement. He says farmers need to be persistent the first and second years. The third year will be better. After five years, Jason is seeing major changes in his soil. Another benefit similar to the second benefit on better drainage, is cover crops are helping tiles run better or function better. He credits that to better structure and infiltration. He said his eleventh benefit is more stable yields. This last year was very trying with the drought. Jason said that they had functional yields and gave the credit to the improved soils, cooler temperatures under cover, and moisture retention. Lastly, he said that his farm is more profitable.
I asked Jason about farming wheat after corn. Some farmers want to till or use vertical tillage after corn for wheat. Jason says a good no-till drill can function fine after corn. He goes diagonal across corn stalks leaving stalks intact. He says he receives excellent stands of wheat. He says farmers need to persist in no-till, and keep growing covers. He also drills all of his cover crops and plants diagonal from the previous crop. I asked him what group type soybeans does he grow. He says that his crops are 30% corn, and 70% are soybeans. He grows group 3s full season soybeans and 5s when double cropped with wheat. The 3s full season beans allow for earlier drilling of cover crops.
He says that he drills covers right behind the combine. His drill is 15 feet wide. He says farmers must make covers a priority. On terminating his covers, he said that he has tried all different heights and maturity. He seems to like late boot stage for grass and mid bloom for legumes.
His soil tests show gains in soil health. Jason stated that in 2014, his SOM averaged 3.7% which is good. I took his recent soil test results in 2017 and averaged on 11 grids and came up with 5.35 or 5.4 % SOM. His soils continue to improve as shown by a 1.65 change in % SOM in three years or approximately 0.55% per year in SOM increase. Jason is yielding the results of persistence and consistency using cover crops with his no-tillage.