Cover crops are coming back in other areas of the country, too. The practice of seeding fields between harvests not only keeps topsoil in place, it also adds carbon to the soil and helps the beneficial microbes, fungus, bacteria and worms in it thrive.

These properties have led philanthropies like the Howard G. Buffett Foundation and the Samuel Roberts Noble Foundation to underwrite research on cover crops, while Monsanto, together with the Walton Family Foundation, recently put up the money to support the Soil Health Partnership, a five-year project of the National Corn Growers Association to identify, test and measure the impact of cover cropping and other practices to improve soil health.

Cover cropping is still used only by a small minority of farmers. When the Agriculture Department asked for the first time about cover cropping for its 2012 Census of Agriculture report, just 10.3 million acres — out of about 390 million total acres of farmland sown in crops — on 133,124 farms were planted with cover crops. The next census won’t be done until 2017, but experts say that the practice has spread. In an annual survey of about 1,200 farmers, the mean acreage reported as being sown in cover crops was 259 in 2014. That was double the mean reported by respondents in 2010, though results are not directly comparable because different farmers may have been involved in the surveys, said a spokesman for the Sustainable Agriculture Research & Education, a federal government program, which conducted the survey.

“We’ve never seen anything taken up as rapidly as using cover crops,” said Barry Fisher, a soil health specialist at the Natural Resources Conservation Service, an agency within the Agriculture Department.

Interest in cover crops is coming from buyers, too. Dan Barber, a prominent chef who uses locally grown foods, has championed incorporating cover crops like clover and millet into cuisine as a way of encouraging farmers to grow them.

The Blue Ox Malthouse in Maine was established to coax farmers there to grow barley as a cover crop, which the company then turns into malt that is sold to the state’s craft beer industry. Half a dozen farmers are producing good-quality barley as a cover crop, and others “are interested in turning the grains they’ve been growing as cover crops into something there’s a value-added market for,” said Joel Alex, Blue Ox’s founder and maltster.