The Rise of Cover Crops

Every few days during summer, usually around dusk, a small plane would cruise low in the sky and release a fine mist over the cotton field by my house. I remember the steady drone of the plane breaking up the evening stillness like the buzz of an unwelcome fly charting a course over a dinner table. The hazy white blanket was a chemical cocktail of pesticides, herbicides, and fertilizers, distributed methodically over the field to ensure a productive harvest. Our house was far enough away from the targeted crops to avoid direct exposure. Others, like my friend Daniel who lived with his family in a small house at the center of adjacent cotton fields, weren’t as lucky. It’s hard to say if he or his family suffered from toxic exposure, but they were clearly vulnerable. Besides the crop duster pilot’s skill and discretion, nothing stopped the chemicals from raining down on his house. And when the toxins settled into the soil, no buffer existed to shield their property from potential leaching and runoff.

cropdusting_tpmartins-1066This was the early 1990s when tobacco, cotton, and soybeans were still huge cash crops in the South and the Midwest. Pesticides weren’t as heavily regulated then and many farmers weren’t as conscientious about limiting their use. Since then, through a combination of more regulation and pressure from environmental groups, the farming industry has reduced the use of harmful chemicals and improved application methods. The resurgence of one farming practice in particular, however, has helped to slash the use of synthetic fertilizers and herbicides. A practice known as cover cropping.

Cover crops are noncash crops (rye, barley, sorghum, buckwheat, turnips, and hairy vetch) that serve a variety of purposes such as maintaining soil erosion, fertility, water, & pests. In addition to reducing the need for herbicides and pesticides, cover crops offer a substantial solution to another harmful byproduct of farming: nitrate and phosphorous runoff. Across the Midwest, nitrate-filled water from farm fields is making drinking water less safe. Phosphorous runoff feeds toxic algae blooms in rivers and lakes, leading to massive “dead zones” from Lake Erie to the Gulf of Mexico. But this runoff is largely preventable. Farmers can (and many have already begun to) plant cover crops that capture nitrates before the pollution runs into streams. A common method is to plant wide, grassy “filter strips” along stream banks. A filter strip is an area of grass or other permanent vegetation used to reduce sediment, organics, nutrients, pesticides, and other contaminants from runoff and to maintain or improve water quality.

Cover crops are also a reliable substitute for the rampant use of pesticides and fertilizer. Modern farming practices like applying herbicides have helped farmers increase yields and reduced labor, but they have also unintentionally interfered with root systems and disrupted underground microbial activity and insect life that are vital to plant and soil health. (Farmers still use herbicides, but they use much less; and they can often do without fertilizer.) As one Iowan farmer, an expert in cover crops, notes: “While the cash crop brings in money and feeds people…the off-season cover crops feed the soil and the hidden universe of microbes within it, doing much of the work done by chemicals on conventional farms. And the more diverse the mix of cover crops, the better the whole system works.”


Planting cover crops and filter strips is not required by law. The Clean Water Act specifically exempts so-called “normal farming practices” like plowing and maintaining drainage ditches. The use of cover crops is still quite rare and would probably not be considered a “normal farming practice”, anyway. Yet, many farmers are taking the initiative to incorporate cover crops into their businesses. Indeed, planting cover has gone from an obscure, small-scale practice to a more recognizable and widely-accepted farming technique.

Some states have embraced the practice more than others. Minnesota, for example, has taken the lead in establishing water rules related to cover crops. This fall, the state’s farmers will be required to maintain a strip of grass (filter strip), an average of 50 feet wide, along many of the state’s streams. The adoption of cover cropping has grown rapidly in Indiana where about one million of the 12.5 million acres of farmland there are planted with cover crops between harvests. A strong collaboration between Purdue University and state and federal farm services gave birth to the Indiana Conservation Cropping Systems Initiative, a program that offers education and research to farmers in the state. In North Carolina, farmers plant winter cover crops like winter wheat and forage radish, a practice with benefits beyond runoff prevention, including richer soil and increased revenue.  Cover crops have also gained ground here in Illinois, a heavy agricultural state.

The expansion of cover crops appears to be a more valuable and effective way to restore soil and protect water than increased regulation. It’s certainly more preferable to farmers. The benefits it can bring are real and not contingent on the outcome of political and legal battles. Let’s hope cover crops continue to rise.

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