Kent Solberg

Kent Solberg, a successful farmer and educator for the Sustainable Farming Association, is showing healthy soil found in non-grazed farmland. A variety of techniques can be used to get similar soil on farmland and pasture. Picture here is U.S. Veteran Tony Norris who farms 25 acres with his wife, U.S. Veteran Charreise Norris near Montrose, Minn. Norris is timing how long it takes an inch of water to soak into the rain-soaked sandy soil. It took about 6 minutes, which is acceptable, said Solberg. Photo by Andrea Johnson.

Soil health is at the heart of crop and garden 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 these questions is the presence of good and active soil biology.

“We can add fertilizers and things like that, 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,” said Kent Solberg, Sustainable Farming Association instructor.

Healthy soil, says Solberg, is about 45 percent minerals, 5 percent organic matter, 25 percent air space and 25 percent water. While he didn’t talk about tiling or the impact of drainage, Solberg pointed to a set of principles that when applied can lead to good soil health.

1) Living roots, like cover crops, provide food for soil microbes that need a moist environment plus air to thrive.

Solberg said that about 90 percent of healthy soil function is created by microorganisms. These subaquatic animals create a biotic glue called glomalin that holds soil particles together to create soil aggregates. The soil aggregates expand and contract to hold water and cycle nutrients.

2) Keeping the soil covered is important to keeping it healthy.

As the rain falls or the wind blows, soil movement occurs to create an environment that doesn’t grow crops well. Soil movement through erosion is also a contributor to soil plant diseases – especially white mold in soybeans.

3) Minimizing soil disturbance by keeping the soil covered also reduces the soil temperature and allows soil microbes to thrive.

A ground cover of residue or cover crops can reduce the soil temperature by 20 degrees and moisture stays in the soil. If the soil temperature reaches 115 degrees F, soil microbes begin to break down. At 140 degrees, microbes die, so a vegetative mulch cover is a good way to keep microbes healthy during drought periods. On a hot day, says Solberg, soil temperatures can easily vary by more than 40 degrees between bare soil and knee-high grass.

4) Crop diversity and rotation also help improve soil health.

There are four major crop types that work well in a diverse cropping setting, he said. These include warm season grasses, warm season broadleaves, cool season grasses and cool season broadleaves. He added that 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,” said Solberg. Highly complex plantings with a variety of plant species results in healthy soil that is very resilient to weather extremes, he added.

5) Finally, bringing livestock onto the farmland is the missing link that can greatly improve soil health and production.

The natural pruning of cover crops, the fertility of fecal material, and the hoof/foot action of livestock often results in a better soil environment.

“We don’t want livestock on any given site more than three days (so the livestock are) leaving adequate residue to protect the soil, to operate that carbon pump, putting those photosynthates, that sugar, down into the soil to feed the microbiology, and it helps,” said Solberg. “What we want to do is leave leaves. We want to leave those solar panels out there to create that photosynthesis.”

All of these principles for good soil health require a strong agronomy education and creativity that go 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.

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