Roots on the Ground

Green is the new black in Iowa fields.

While Iowa’s rich black soil remains a treasure, guarding it from erosion and sequestering nutrients have become a priority for more and more farmers.

Cover crops were nearly nonexistent a decade ago, but today they cover about 3 million acres of farm ground between fall harvest and spring planting. The off-season crops reduce nitrogen and phosphorus loads by about 30%, on average.

“The reason I started with cover crops was they sequester nutrients,” said Dean Sponheim, a farmer in Mitchell County. “There’s nitrogen, phosphorus and potassium being released when we don’t have corn and soybeans in the field, and I would love to have the rye crop pull it up, and that’s what happens. I use it as a bank.”

Like many who now seed cover crops, Sponheim describes a complete change in mentality. He used to think seeing black dirt between rows was beautiful. The same sight today makes his stomach turn.

Instead, he wants to see a lot of residue on the soil between rows.

But he is also quick to explain to other farmers that the benefit of cover crops goes well beyond the environmental impact. “We actually see yield increases,” he said. “And our 8-year study shows we’re seeing a 7-bushel a year average increase on corn. About a half a bushel on beans.”

He attributes those gains to healthier soil.

Iowa’s Nutrient Reduction Strategy aims for millions of additional acres to be protected by cover crops. The message of profitability in connection with soil and water quality is persuading more farmers to keep roots in the ground.