Progress: Every time a farmer grows cash crops, including corn and soybeans, the plants extract valuable nutrients (nitrogen and phosphorus) from the soil. To keep yields stable, the amount of nitrogen applied to farmland in the form of synthetic fertilizers has risen more than 300 percent in the last 60 years. And between 1973-2014, as industrial agriculture has risen to prominence, farmers have sprayed more than 3.5 billion pounds of glyphosate-based herbicides to combat invasive weeds. With domestic farmers’ increasing dependence on chemical cocktails, the US food system is now facing a nutrient runoff and soil erosion crisis. But all hope is not lost. In the past decade, the percent of US cropland planted with cover crops, which keep fields covered between growing seasons, has increased by more than 50 percent, from 10.3 million acres to more than 15 million. And with less than 5 percent of the nation’s total cropland planted with cover crops, there is still plenty of room for continued growth.
The recent momentum behind the regenerative technique presents an opportunity to re-orient our approach to farming from one that emphasizes chemicals to one that emphasizes biology. Cover crops act as a Swiss Army knife in the variety of purposes they can fill. Legume cover crops (red clover, vetch, peas, beans) can generally fix 50-150 pounds of nitrogen (N) per acre. And non-legume cover crops, including cereals, forage grasses, and broadleaf species, “trap” soil nitrate that would otherwise be subject to losses by leaching or denitrification. This low-cost tool offers farmers a nature-based method to achieve an array of agronomic benefits, which include but are not limited to:
- Increasing land productivity: Farmers can expect a 3 percent increase in corn yields and a 4.9 percent increase in soybeans after five years of cover crop use. By keeping live roots in the ground year-round. cover crops create nutrient pathways from the sun to the soil while reducing nitrogen losses by 48 percent. After termination, cover crop residue can also block sunlight from weed seeds, providing increased suppression into the cash crop growing season. And the spring cover crop growth can also be repurposed for forage, making it ideal for integrating livestock. Grazing cover crops stimulate higher forage productivity and allow animals to return nutrients to the land in the form of urine and manure. The biomass left over after harvesting and grazing can be reapplied to the soil, feeding minerals back into the ground.
- Providing weather resiliency: The more erratic the weather, the more benefits cover crops provide. During times of low precipitation, the mycorrhizal fungi that build up in the soil help the plants extract more water and nutrients. In 2012, for example, when farmers across the corn belt and parts of the Southwestern US faced a prolonged drought, those who had planted cover crops fared significantly better than those who had not – yielding 9.6 percent more corn and 11.6 percent more soybeans. And when facing intense rainfall, having a diverse set of roots in the ground allows the soil to act as a sponge to hold rainwater via evapotranspiration.
- Sequestering carbon: Cover crops are an important soil carbon sequestration strategy. If planted across 20 million acres, cover crops could sequester approximately 60 million metric tons of CO2-equivalent per year, offsetting the emissions from 12.8 million passenger vehicles. This practice uses photosynthesis to transform atmospheric carbon into food that nourishes crops, soil, and livestock. Moreover, including cover crops in agricultural rotations has been shown to increase soil organic carbon by 15.5 percent.
Even with the uptick in cover crop adoption, many producers assume that they are not economically able to take land out of production, even for one growing cycle, for a future ecological payoff. To overcome this obstacle, state agriculture departments and federal initiatives – such as the Conservation Stewardship Program and the Environmental Quality Incentives Program – have begun offering financial incentives and insurance protection for planting cover crops. Meanwhile, for-profit companies like Cover Crop Exchange, Covercress, and Agrisoma are commercializing marketplaces and “cash cover crops” that can help farmers improve land fertility AND profitability. Accelerating the adoption of cover crops will happen if we can show producers how this practice is not only a long-term investment in soil health but a tool that can improve their bottom line.
Watch: Four billion years of evolution have created the dirt that recycles our water, gives us food and provides us with shelter. One teaspoon of dirt contains a billion organisms working in perfect harmony to sustain a series of complex communities that are a part of our daily lives. In return, humanity has endangered this precious resource through the use of extractive agricultural practices. DIRT! The Movie tells the story of Earth’s most valuable and underappreciated source of fertility – from its humble beginning to its rapid degradation. But the overall message is one of hope. The film, which is narrated by Jamie Lee Curtis, travels around the world capturing the stories of visionaries discovering new ways to mend humanity’s broken relationship with soil.