“My cover crop wasn’t green this spring!” Don Wirth’s answer to what sounded to him like a complaint was, “Go dig!”
His point: when annual ryegrass is established in the fall, it quickly sends roots down below a foot, even in fields that haven’t had a cover crop before. (In successive years, annual ryegrass roots can send roots to deeper than 40 inches, even when there’s only a couple of inches of top growth!) It is those roots that help prevent erosion. But that’s only the beginning. Deep rooting breaks up compaction, improves permeability. That’s still only the beginning. The biggest benefit is that cover crops improve soil biology, including a healthy population of earthworms and microorganisms. When that happens, crops thrive, production increases and costs for inputs go down.
A few years ago, he visited a Midwest farm in the spring, where no cover crop was evident on the surface. And yet, walking across the field, Don was able to point out where the annual ryegrass had grown the year before. It was as if a line had been drawn on the land. Cover crops had already begun to change the biology of the soil beneath. “I’m guessing that the field had very low organic matter content, so the addition of even a year’s worth of cover crop will make a significant difference in how the soil looks and feels,” he said.
Wirth, an Oregon grass seed farmer said there is a lot of reliable information now about the value of cover crops. But he heartily suggests that farmers be more informed about the health of their soil. He recommends reading Gary Zimmer’s book Biological Farmer, written in 2000. Here’s a short excerpt from the book’s description:
Biological farming does not mean less production; it means eliminating obstacles to healthy, efficient production. It is a safe and sustainable system designed to keep production up.
Wirth also suggests becoming more in touch with improving your soil’s health. He said starting with an inexpensive Solvita test (about $150) will give you some basics.
The test uses a couple of soil probes loaded with a certain kind of gel that reacts to soil chemistry. Among other things, the Solvita measures carbon dioxide emissions…mostly due to microbial respiration. The level of microbial activity indicates the amount of active organic matter that is being broken down and the amount of nutrients being released.
Measuring year after year will give you a chart of the growth in soil biology and organic matter. Overlay that on a record of crop yields and you’d have pretty convincing evidence about the connection between cover crops,
soil health and profits.