Second-generation farmer Brad Cochran raises corn, cotton, soybeans, and wheat on 4,000 acres on the Madison and Gibson County line in Tennessee. Up until the 1980s, Brad says he farmed like everyone else – with conventional tillage methods. In that era, erosion was just an accepted result of farming, he said.
Brad now samples his soils in 5-acre grids, making nutrient management decisions accordingly, and rotates his crops on a three-year basis. In 2016, planted 3,000 acres in multi-species cover crops and another 1,000 acres in cereal rye. Brad only receives financial assistance on approximately a third
of his acreage.
Brad says that late in the 1980s and in the early 90s, his family began no-tilling cotton with a bushel per acre of wheat for a cover crop. They would aerial seed the wheat via an airplane. In the mid-1990s, he attended a national no-till conference in the Midwest, which peaked his interest in annual rye grass as a cover crop.
He remembers his grandfather growing cover crops and terminating them by plowing. When asked what his driving force in using a permanent cover crop system and no-till, he said “erosion reduction.” He also says adding crop rotations and leaving corn residues has added to the soil organic matter (SOM) significantly.
Brad’s 2012 soil samples found an average pH of 6.3. His SOM ranged from several samples between 1.1 to 2.5 percent, and his cation exchange capacity (CEC) levels ranged from 5.2 to 11.5 meq per 100 grams of soil. His estimated nitrogen release (ENR) – that is, the potential nitrogen available from soil organic matter decomposition – ranged from 66 to 94 pounds per acre.
By 2015, his average pH was 6.4, SOM ranged from 1.7 to 3.6 percent, CEC ranged from 6.3 to 21.6 in meq per 100 grams of soil (higher CEC levels mean the soil can hold more nutrients for latter plant availability), and ENR ranged from 72 to 100 pounds per acre. His infiltration rates average 7″ inches per hour.
Brad also sampled his fields in 2015 using the Haney Soil Health Test. In two seemingly identical fields, Field A had nutrient value of $96.90, while Field B had $81.00. Nutrient value is derived from levels of recycled nitrogen (N), phosphorus (P), and potassium (K). In Field A, nitrate was 26.8 ppm. In Field B, it was 14.1 ppm. Organic N was 30.6 ppm in Field A and 32.9 ppm from Field B.
The Haney test also provides a respiration test measuring CO2-C (carbon dioxide – carbon). Field A indicated 96.4 ppm CO2-C in 24 hours compared to 37.2 ppm CO2-C from field B. In other words, more respiration indicates higher biological activity. Another component is water extractable carbon (C) which indicates food availability (active carbon) for soil microbes. Field A had 150.9 carbon in ppm compared to Field B with 167.4 carbon in ppm.
Based on the results of the Haney tests, Brad increased the proportion of grass in Field A to increase soil life activity and meet the field’s higher need for available C and N. As Brad increases his grass percent in the cover crop mix, more C and N will feed the higher activity. The result will be more soil aggregation and nutrient cycling. Field B calls for a 50 percent mix of grasses to legumes and brassicas. This will help this field increase soil life activity and continue to decompose C and provide N cycling to plants. All of the nutrient cycling will result in less inputs.
About eight years ago, Brad saw the advantages of going to 1-3 species on certain fields. He planted black oats, rye grass, and crimson clover. Five years ago, he continued with rye grass, black oats and crimson clover. He added forage radishes to the mix. The last two years he has planted 20 pounds per acre of cereal rye, 25 pounds of black oats per acre, 5 pounds of crimson clover per acre and 3 pounds of forage turnips per acre. He has added canola to the mix one out of the last two years. He moved away from rye grass prior to soybeans due to disease risk in soybeans. He plans to interchange rye grass and cereal rye. Rye will be used in the mix prior to planting soybeans, and rye grass will be used prior to planting corn. He likes the deep roots from rye grass.
Brad uses three drills after crop harvest to seed his cover crops. If wheat-beans are late harvest, he occasionally will aerial seed cover crops. His objective is to grow cover crops as late as possible. He normally sprays a burn down herbicide five days to a week before planting. He knocks the cover down with the planter and uses roll cleaners when planting corn, but not with soybeans.
To illustrate the benefits of deep roots from rye grass, Brad had some conservation structure work done on a field. The field yielded 70 bushels of corn per acre in the area where soil was disturbed. After corn, rye grass was planted for winter cover, and then corn was no-tilled in desiccated rye grass cover. The field yielded 150 bushels per acre. The yield more than doubled due to the rye grass cover. The next year, rye grass was planted again, and corn followed. In all three seasons of corn, irrigation was applied as needed.
The second season planted in rye grass, the corn yielded 200 bushels per acre. The rye grass loosened the soil, the roots brought up nutrients, and the soil held more moisture during the season. There was no need for tillage because the roots had healed the hard-compacted soil. Most people tend to revert to tillage when the soil is hard and degraded. What the soil needs is carbon and better infiltration from plants.
Brad advices farmers to commit to using cover crops and letting them growing as long as possible in the spring to yield the benefits. He has seen his SOM increase in three years from 2.5 to 3.6 percent, better water infiltration during and after rainfall events, and no signs of erosion on the farm. He said there are over 40 earthworms per square foot in his soils now (while in tilled fields, it is difficult to find five earthworms per square foot), and the soils are generally much cooler thanks to the cover crops.
Typical inputs, such as high-salt chemicals and fertilizers, are expensive and not the best for the soil, he said. “They tend to make the soil hard with less life.”