Soil health is at the heart of crop production. It answers the “why’ questions like, “Why is there more ponding in one field vs. another?” or “Why does this field produce larger yields than another?” or “Why did this field produce a crop in drought conditions while other fields failed?”
The answer to those questions is the presence of active soil biology.
“We can add fertilizers and things like that,” said Kent Solberg, an instructor with the Sustainable Farming Association of Minnesota. “But in a side-by-side comparison, if we have good healthy soil biology seedings are going to be up faster, stronger, bigger and fuller.”
Healthy soil is about 45 percent minerals, 5 percent organic matter, 25 percent air space and 25 percent water, he said. Living roots like cover crops provide food for soil microbes that need a moist environment plus air to thrive.
About 90 percent of healthy soil function is created by microorganisms. Those subaquatic animals create a biotic glue called glomalin that holds soil particles together to create soil aggregates. Soil aggregates expand and contract to hold water and cycle nutrients.
Keeping soil covered is important to keeping it healthy. As rain falls or wind blows, soil movement occurs. It creates an environment that doesn’t grow crops well. Soil movement through erosion is also a contributor to plant diseases – especially white mold in soybeans. Keeping soil covered also reduces soil temperature and allows soil microbes to thrive.
A ground cover of residue or cover crops can reduce soil temperature by 20 degrees and moisture stays in the soil. If the soil temperature reaches 115 degrees, soil microbes begin to break down. At 140 degrees microbes die. A vegetative mulch cover is a good way to keep microbes healthy during drought periods. On a hot day soil temperatures can easily vary by more than 40 degrees between bare soil and knee-high grass.
Crop diversity and rotation also help improve soil health. There are four major crop types that work well in a diverse cropping setting, Solberg said. Those include warm-season grasses, warm-season broadleaves, cool-season grasses and cool-season broadleaves. Some soil-health experts say farmers should really be planting 15 different species of plants in a three-year crop rotation.
“That almost sounds undoable, but when we look at the tools we now have with cover cropping it’s not that hard to do,” Solberg said.
Complex plantings with a variety of plant species results in healthy soil that is resilient to weather extremes.
Bringing livestock onto farmland is a missing link that can greatly improve soil health and production. The natural pruning of cover crops, the fertility of fecal material, and the hoof or foot action of livestock often results in a better soil environment.
“We don’t want livestock on any given site more than three days,” Solberg said. “(So the livestock are) leaving adequate residue to protect the soil (and) to operate that carbon pump. (They put) those photosynthates, that sugar, down into the soil to feed the microbiology, and it helps. What we want to do is leave leaves. We want to leave those solar panels out there to create that photosynthesis.”
Good soil health requires a strong agronomy education and creativity that goes beyond a corn-soybean rotation with tillage. Solberg is part of a growing body of agriculturists who believe farmers are ready to adopt cover crops, livestock and more for good soil health.
Visit www.sfa-mn.org for more information.