Progressing from Single Species to Multi Species Cover Crops to Improve Soil Health
Brad Cochran is the 27th in our series of Profiles of Soil Health Heroes. I visited Brad on November 4, 2016 with Brad Denton, NRCS District Conservationist, Madison County. Brad farms in Madison, Carroll, and Henderson Counties, Tennessee. Brad has essentially farmed his entire life. He is a second-generation farmer. His operation is approximately 4,000 acres. Brad and his family produce corn, cotton, soybean, and wheat farming operation. In 2016, he did not plant any cotton. Brad grows his corn on 30" rows, soybeans on 15" rows, and cotton on 38" rows. He said up to the 1980s, they farmed like everyone else at the time and used conventional tillage methods. Erosion was just an accepted result of farming.
Brad's nutrient management plan involves annual grid sampling in 5-acre blocks or grids. He follows a three-year rotation of liming. He limes by soil test and applies it with variable rates. He grows both full season soybeans as well as double cropped soybeans after wheat, which make up 20-25% of his soybean crop. Brad participates with NRCS. Brad now believes in using cover crops. He currently has planted in 2016 3,000 acres in multi species cover crops. Another 1,000 acres are in cereal rye. Brad only receives financial assistance on approximately 1/3 of his acres. He sees the importance of cover crops, and invests the rest with his funds.
He said in the late 1980s to the early 90s, they 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 Mid-West. That led to his interest in annual rye grass as a cover crop. He said that he remembers his grandfather growing cover crops. Of course, his grandfather plowed the cover under. I asked him what were the driving forces to cause him to go to a permanent cover crop system and use no-till? He said that as he no-tilled his cotton, he saw all erosion reduced as the soil was covered compared to conventional tillage with cotton. He also saw the need to add rotations to his then cotton-dominated crop production system. Adding corn added residues and added more crop biomass which adds to the soil organic matter (SOM). He saw the need from conferences to add cover for erosion control, and to increase SOM. He ultimately wanted to sustain the soil.
Brad soil tests, as stated above, are in 5 acre grids. His 2012 samples in one field showed pH as an average of 6.3. His SOM ranged from several samples of 1.1% to 2.5%. His CEC (cation exchange capacity) ranged from several samples from 5.2 - 11.5 meq per 100 grams of soil. His estimated nitrogen release (ENR) ranged from 66 to 94 pounds per acre. That is the potential nitrogen available from soil organic matter decomposition. His 2015 samples show improvements in soil health. His 2015 SOM ranged from 1.7 to 3.6%. His CEC ranged 6.3 to 21.6 in meq per 100 grams of soil. His ENR ranged from 72 to 100 pounds per acre. His average pH was 6.4. These results show higher SOM on all fields. All fields have increased CEC which means the soil can hold more nutrients for latter plant availability. Higher ENR means more nitrogen will be available due to higher SOM and better quality SOM resulting in more nitrogen available from decomposing soil carbon or SOM.
Brad sampled a field in 2015 using the Haney Soil Health Test. He took a particular field and split it into two for the samples. No major inherent soil differences. We will call each sample field A and B. Field A had nutrient value of $96.90 while field B had $81.0. This is the value from recycled nitrogen (N), phosphorus (P), and potassium (K) as result of increased SOM. Nitrate in ppm is 26.8 and 14.1 for fields A and B, respectively. Organic N was 30.6 ppm from field A and 32.9 ppm from field B. Field A has more nutrients available due to nutrient cycling. Both fields have value from nutrient cycling. Farmers should consider cover crops to cycle nutrients instead of just depending on chemical inputs for nutrients. Soil organic matter is decomposing in a healthy manner to cycle nutrients giving Brad a potential savings in nutrients. 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. This shows biological activity. Higher activity shows healthier environment of soil biology. The more respiration correlates with higher activity. Another component is water extractable carbon (C) which indicates food available (active carbon) for soil microbes. Field A had 150.9 carbon in ppm compared to Field B with 167.4 carbon in ppm. Same findings for water extractable nitrogen, field A had 14.5 ppm in N and Field B had 17.9 N in ppm. Carbon and nitrogen ratio was 10.4 in field A compared to field B is 9.3. Soil health number which is given based on water extractable C, N, respiration, and carbon to nitrogen ratio. Field A had a 12.6 compared to field B had 9.4. Field A has more available nutrients, higher respiration, somewhat lower C and N and somewhat higher carbon to nitrogen ratio. Field B has the higher quality of C and N and better carbon to nitrogen ratio but lacks the respiration and less nutrients which rates it lower in soil health. Both fields are showing gains in soil health from Brad's management. Soil health numbers greater than 7 show good trends.
Soil tests like the Haney test can assist farmers in making adjustments. The Haney tests recommends that Brad increases a higher percent of grass or carbon to field A. That side of the field has higher soil life activity and has a 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% mix of grasses to legumes and brassicas. This will help this field increase in soil life activity and continue to decompose C and provide N cycling to plants. All of the nutrient cycling will result in less inputs.
After attending the national no-till conference, Brad farmed a few years using one species of cover crop. He was drilling the rye grass. 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. He normally drills 100% of 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. He uses roll cleaners when planting corn. He does not use roll cleaners when planting 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. Roots 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 from plants taking advantage of energy flow, sunlight. Plants convert sunlight into carbon (sugars). Sugars are trans located to roots. The roots leak carbon, and feeds soil microbes. Larger soil life feeds off of soil microbes. The plant dies and then soil life decomposes the plant material. The soil food web aggregates the soil which results in crumbly or blocky soil structure. The soil is aggregated by soil biology glues that provide stability to the soil. This results in good air and water movement into and within the soil. The stability of the soil allows the soil to be stable when it rains, reducing soil erosion. All of these factors enable the soil to infiltrate water at a much quicker rate compared to no-till soil without covers or soil that has been tilled. NRCS has run some single ring infiltration tests. They recorded 7" per hour on infiltration rates. Some averages for no-till without cover are 2-3" per hour. Tillage fields average 1/4 - 1/2" per hour. Having a better infiltration rate correlates to better use of water and less runoff.
I asked Brad what are the benefits of him using continuous no-till, and planting cover crops. He said that first and foremost, people once committing to cover crops need to keep 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%. He has observed better water infiltration during and after rainfall events. There are no observable signs of erosion on the farm. Brad describes his soil as having better tilth (crumbly structure), not as hard, and fluffy. The soil has a strong sweet earthy smell. Earth worms are prevalent when moisture is available. He said that measurements recently showed over 40 earthworms per square foot. In tilled fields, it is difficult to find five earthworms per square foot. Earth worms are a general soil biology indicator. As earthworms thrive, then normally other soil life thrives. The soil retains more moisture. The soil is cooler in the summer under covers compared to no-till without covers.
I asked Brad why should farmers reading this article try cover crops and no-till? He said input costs continue to climb. Management practices that farmers use should make the soil more sustainable. He said that typical inputs such as high salt chemicals and fertilizers are not the best for the soil. They tend to make the soil hard and with less life in the soil.
Brad has evolved as a conservation farmer since the 1980s. He has learned the need to use continuous no-till. He began slowly with one species cover crop to consistently using five to six species today. He has assessed his soil by using standard soil test and a soil health test called the Haney tests. These tests conclude that SOM is increasing, more nutrients are available, and soil biology activity has increased. Brad has observed more life in the soil as shown by high numbers of earthworms. He has also measured his infiltration rates and has seen a rate of 7" per hour. Brad's commitment to cover crops and no-till with good nutrient management has improved his soil health as well as his profit margin. Better soils equal better profits.