Crop growers face tillage challenges as they balance production and conservation in the same fields.
Aggressive tillage blackens the soil so it can absorb sunlight for the short growing season. Practices that minimize the impacts of corn root balls, excess stover, and the potential for disease are needed.
But conservation practices are also needed to stop soil erosion, store carbon and keep the soil healthy to produce high quality crops and good yields.
“In reality, we’re still losing soil,” said Jerry Hatfield, director for the USDA National Laboratory for Agriculture and the Environment. “Even with our conservation tillage systems, we have this problem with very intense storms we’ve been getting in the spring.
“We have a lot of runoff before we have a growing crop. Even those things that leave 30 percent residue still have quite a bit of soil wash coming off of them.”
The U.S. farmer has adopted extensive reduced tillage systems on about 10-20 percent of tilled acres, Hatfield said, although the Natural Resources Conservation Service figures some level of conservation tillage is used on 50-60 percent of farm land.
When comparing 1980 with 2010, Hatfield thinks the U.S. farmer has reduced soil erosion. Soil organic matter is remaining at a steady level, and that’s a result of conservation practices. Improving the soil needs to be a continuing goal for every farmer, though.
“We probably haven’t improved as much as we need to in terms of saving our soil,” he said.
Adopting reduced tillage and using cover crops are two methods for improving soils. The addition of small grain cover crops would protect the soil in the late fall and early spring.
“The protection of the soil in the early spring across the Upper Midwest is more critical than at any other time of the year,” he said. “We continue to have higher intensity storms during our springtime when we have very little crop to take up any water, and a limited amount of protection of the soil surface from the storms.”
Cover crops also increase the extraction of carbon from the atmosphere. A cover crop removes carbon, puts it back into the soil, and increases the amount of carbon storage within the soil system.
“Because we change the type of rooting systems (small grains) that we use as our cover crop, we change the whole dynamic of the soil biology, because we have different root materials out there, and have a more fibrous root system than if we have just corn or soybeans,” he said. “We are changing a number of things dramatically that are for the positive in terms of improving our soils over time.”
Researchers are studying the potential for aerial seeding a cover crop following harvest. Another possibility is planting a living mulch, such as clover, that would remain dormant through the growing season but would grow very early in the spring.
For continuous corn, Hatfield would like to see more research conducted on leaving the previous year’s corn stalks and moving the planter over 10-15 inches.
“In actuality, where you’re not disturbing the old root mass and leaving that stalk standing up - that traps the snow and prevents the residue from moving over, and can result in significant increases in organic matter,” he said. “That’s a very simple change in terms of a cropping system out there.”
A planting configuration change is just one item that farmers might want to explore to improve soil health.
To improve yields, soils need high quality biological systems, he said. By managing soil microbial populations, farmers can allow microbes to digest the organic matter in the fields.
“The biological glue is what creates the stable aggregates that make the soil more resistive to erosion,” he said. “We need to think about what it means to adopt systems that allow the soil microbial system to be as efficient as possible.”
As producers push to grow over 200 bushel per acre corn, they will need high quality and healthy soils to accomplish their goals. Finding ways to maximize the water that is available to dry land corn when it is needed is a significant task for farmers too.
“You’re not going to achieve sustainable high yields consistently without allowing that soil to support the plant so it doesn’t lodge, but also supply nutrients and water,” he said. “A lot of our systems - we create the potential yield, but we have a hard time fulfilling that potential, because the plant has limitations.”
Optimizing genetics, the suite of protection systems that are added to a plan, and the soil system are all needed to allow the crops to have access to as much nutrients as they can get.
As producers look at the second decade of the 21st Century, they may well have to adopt varying management practices to achieve their yield goals across the farmlands. It’s very likely those practices will include a combination of tillage, conservation tillage, no tillage plus cover crops to maintain the very valuable farm soils.