Flash flood? Flash drought? Time for a little slow soil

The U.S Drought Monitor released its latest figures yesterday, verifying what we already knew: Minnesota is extremely dry. In fact, 55 percent of our state now falls under the “severe drought” or “moderate drought” category. Over 60 percent Minnesota’s subsoil moisture is “short” or “very short.” The National Drought Mitigation Center reported that in August Minnesota was the fastest growing drought area in the U.S.

We are suffering through what weather-watchers call a “flash drought”—a situation where one can’t buy a rain after a period of significant wetness. Remember this spring and early summer when the memory of the 2012 drought was washed away by seemingly incessant rains? That faucet was shut off by mid-summer, and now we have some pretty sorry looking crop fields and pastures in parts of the state. Pile on the fact that the planting of most row crops was delayed by all that rain (and snow) this spring, and farmers across Minnesota are hoping against hope that the first killing frost will be a latecomer this year.

Are we helpless in the face of all this whiplash weather? Maybe…maybe not.

In late August I accompanied some 40 farmers, scientists and soil conservationists to south-central North Dakota’s Burleigh County, where we saw what folks are doing to slowly, but gradually, build their soil’s biological health under less than ideal weather conditions. The trip, which was sponsored by the Minnesota Natural Resources Conservation Service (NRCS) and the USDA’s Sustainable Agriculture Research and Education program, is the latest effort on the part of the state’s soil conservationists to counter all that massive erosion we’ve seen in recent years. There are signs that conventional erosion control methods like terracing and grassed waterways aren’t enough as severe weather events become more common.

“We need to take the next step in soil conservation,” said Douglas Miller, Minnesota’s NRCS soil coordinator and one of the organizers of the North Dakota tour.

What the Burleigh County Soil Health Team has found is that a combination of cover crops, rotational grazing and no-till farming can do something many soil scientists once felt wasn’t possible: increase soil’s natural ability to build its own fertility, resist erosion and make better use of any precipitation that falls out of the sky.

That last characteristic is particularly key in an area that generally gets 16 inches of precipitation annually—a foot less than what Minnesota gets in a typical year. The Team, which consists of local farmers, NRCS experts, Soil Conservation District personnel and scientists from the USDA’s Northern Great Plains Research Laboratory, has attracted attention from around the world; just this summer, visitors from Russia and France came to Burleigh County to grub around in the soil.

Visitors from both near and far are having a lot of their assumptions turned upside down. For example, in August the Minnesota contingent saw un-irrigated corn, pastureland and hay ground that seemed to be thriving despite the lack of measurable rain during the previous eight weeks.

Crop fields and pastures where soil organic matter levels had been built up (organic matter is a key driver of healthy soil biology) were often bordering conventionally managed plots, providing a striking contrast in the 90-degree plus temperatures.

“Our pastures would look like that if we hadn’t changed things,” said Burleigh County farmer Mike Small while pointing to a neighbor’s grassland that was brown and as smooth as a billiard table. Small’s nearby pasture was ready to be grazed again after a brief rest provided by his rotation system. The contrast between corn fields was equally stark: members of the Soil Health Team had good, vibrant stands; their neighbors not so much.

All that biological activity created below ground by a diverse mix of plants (and roots) develops stable soil aggregates, which can soak up and store water instead of sending it running off the surface. But another key advantage to keeping the land covered with well- managed pasture grasses and cover crops is that they provide shade during the depths of summer and during those periods early and late in the year when row crops aren’t growing. That can lower temperatures enough to boost the soil’s ability to retain moisture even more.

Miller measured soil temperatures in several Burleigh County fields during the tour—one reading taken two inches beneath bare ground clocked in at 96 degrees; two inches down in a cover-cropped field it was a cool 67 degrees.

Building soil health not only makes it possible for the land to better retain and make use of any moisture that’s available during dry stretches, it also means fields can better soak up and store precipitation during wet periods.

One photo that has been widely circulated in Burleigh County is of farmer Gabe Brown’s fields after 13 inches of rain fell in 24 hours. The photo shows no standing water on this low-lying field, even though plots on neighboring land are inundated. Brown has created a soil profile that allows water to infiltrate efficiently, according to Kristine Nichols, a soil microbiologist at the Northern Great Plains Research Laboratory.

And unlike a field that’s been drained through artificial tiling—sending water at rocket speed through the profile and eventually downstream—Brown’s fields retain that moisture in the system, meaning plants can access it during drier periods. It also means less water runs off the surface of the field, carrying wayward soil and other pollutants with it.

Building the kind of rich soil biology Gabe Brown obviously has takes years, but he and other Burleigh County farmers say they will never go back to the quick fixes provided by relying exclusively on high dosages of petroleum-based fertilizers and other inputs. Those inputs may provide record yields in the good years, but these farmers are instead going for the kind of sustainable production that’s consistent, even when the weather goes sour, which it seems to do more often than not these days.

“We had for so long forgotten about what was going on below-ground,” said crop and livestock producer Jerry Doan as he examined a clod of dark, fragrant soil that had been spaded up from one of his fields planted to a cocktail mix of cover crops.

At one point during the tour, Soil Health Team members used a precipitation simulator to compare the impacts of a one-inch rain on trays of soil representing everything from native rangeland and rotationally grazed pastures to cover cropped no-till fields and conventionally farmed plots.

Water penetrated the trays growing grasses and cover crops and percolated into catch jars hanging underneath. The surface of the conventionally farmed tray was muddied, but little water was in the jar underneath. In contrast, a jar that caught surface runoff from the conventional tray was heavy with muddy water. When the pan was flipped over onto the ground, it was clear only the first half inch or so of soil was wet; the rest was a gray powder.

“You’ve just made a drought,” quipped Jay Fuhrer, district conservationist for the Burleigh County NRCS.

After Fuhrer’s comment, several Minnesota farmers relayed stories of getting three-inch rains and having droughty conditions just a few days later. “That rainfall simulator was a real eye opener,” said one Rice County crop and livestock producer later.

This is no magical bullet being shot across the fields of Burleigh County. There are limits to what even the healthiest soil can put up with when floods and droughts of Biblical proportions engulf a region. But as the tour bus crossed the Red River back into Minnesota where acre-after-acre of yellowed, drought-stressed corn faded in the summer heat, it was clear that when a bit of natural resilience is gradually built into the soil, extreme weather doesn’t always have to be a growing season’s death knell.

“I have worked with irrigators for 20 years and I have never seen a corn crop look this good with eight weeks of no rain,” Brad Wenz, a soil conservationist for the Stearns County Soil and Water Conservation District, told me later. “There is something going on there.”

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Brian DeVore's picture
Brian DeVore