Teaming with Soil Microbes (part 1)

Posted by .

On a crisp morning in September, North Dakota farmer Gabe Brown held two handfuls of soil and searched for signs of life—theoretically not a difficult task considering one teaspoon of humus contains more organisms than there are humans in the world. But many of the bacteria and invertebrates that lurk in the dark basement of our farm fields exist visually only in the world of high-powered microscopes. So Brown, a compact ball of energy who can somehow combine references to soil biology, farm policy and animal husbandry in the same sentence, uses a less scientific assessment method to compare and contrast the two handfuls—one from his field, the other from a neighbor’s.

“When you grab this soil there is no structure,” says Brown, referring to his neighbor’s soil. Indeed, it has a slabbed, compacted look to it, indicating there isn’t much room for worms and roots to facilitate transfer of water and nutrients. It’s also a lighter color than Brown’s darker soil, which is the consistency of cottage cheese. “If you have this dark color, you know you have organic matter. I look at it as an investment.”

It’s an investment in a good crop—just a few feet away stands a field of corn that’s emerged from Brown’s rich soil, and it’s thriving, a rarity this year in a part of North Dakota that has been hit especially hard by drought. But to Brown, that healthy soil represents more than more bushels in the bin. It’s also an investment in his farm’s long-term viability and the future of his entire community—human and natural.

The idea that healthy soil is an investment, not just one of many tools, has led Brown and his neighbors to develop a farming system that combines some of the most exciting advances in sustainable production systems—conservation tillage, multi-species cover cropping, mob grazing and frequent rotations. This system, which is evolving, combines cutting-edge soil science with the desire on the part of natural resource professionals to no longer accept a Band Aid approach to conservation. It also shows how teamwork fueled by a holistic, big picture view of agriculture can produce a farming system that benefits land, farmers and communities.

“What Brown and the others he is working with are doing is one of the most exciting and revolutionary in-the-field developments in agriculture today,” says Richard Ness, a Land Stewardship Project staff member who has worked with sustainable farmers throughout the Midwest and who has spent time in south-central North Dakota, where Brown farms. “They’re pushing scientists, conservationists and sustainable agriculture in general to a new level.”

Getting at the root of the matter

At the core of this story is a change in attitude toward soil—perhaps one of the most taken-for-granted resources around. Consider, for example, how Jay Fuhrer used to do his job. Fuhrer is the Burleigh County district conservationist for the USDA’s Natural Resources Conservation Service (NRCS). Burleigh County lies near the section of the Missouri River where it passes through the south-central part of North Dakota. Here the flatness of the state gives way to a more rolling landscape—a landscape known for wheat, “wild” pastures that contain native species such as big bluestem, hay ground and, in the past decade or so, corn. This part of the state receives on-average 16 inches of rain a year, making water a dear resource. So for many years Fuhrer and other resource professionals focused on short-term efforts to get more water into the soil profile and keep it where plants could use it.

“We had accepted a degraded resource,” Fuhrer recalls as he sits in his office in Bismarck, just a few miles from Brown’s farm. “And when you accept a degraded resource you generally work from the viewpoint of minimizing the loss. And so we would apply a lot of practices.”

Fuhrer’s specialty during the 1980s and early 1990s was putting in grassed waterways in an attempt to keep water from running off so quickly. It helped, but didn’t get at the core of the issue: why was that water not infiltrating the soil in the first place?

“In retrospect very few of those waterways were actually needed,” he concedes.

What farmers like Brown and soil scientists in the area were starting to figure out was that the production system that had come to predominate—extensive tillage, low crop diversity, no cover crops, livestock kept out all-season long on overgrazed pastures—was compacting the soil to the point where little water could make its way beneath the surface. It was also sharply reducing the amount of soil organic matter, which drives the entire soil food web. Unbroken prairie soils can have as much as 10 percent to 15 percent organic matter. But because of intensive tillage, Midwestern soil organic matter levels have plummeted to below 1 percent of total soil volume in some cases. This means the soil has little opportunity to cook up its own fertility via the exchange of nutrients, making it increasingly dependent on applications of petroleum-based fertilizers.

Learning from failure

There is a photo that has acquired almost legendary status in Burleigh County. It shows one of Gabe Brown’s fields after 13 inches of rain fell in 24 hours. The picture 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 quite efficiently. 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. Such a healthy water cycle requires a healthy biological food web.

Kristine Nichols, a soil microbiologist at the USDA’s Northern Great Plains Research Laboratory in Mandan, N. Dak., says this photo is a prime indicator that farmers like Brown are able to increase their organic matter to the point where it is able to, for example, make better use of water. As soil organic matter increases from 1 percent to 3 percent, soil’s water holding capacity doubles. During the past decade or so, Brown has more than doubled the organic matter in some of his fields, raising it from less than 2 percent to nearly 5 percent.

Nichols says that as a soil scientist she was taught that a farmer couldn’t have a positive impact on soil organic matter in a typical lifetime.

“We were told this was something we couldn’t change, except in a negative way. Now we realize we can change organic matter,” she says while sitting in her office across the Missouri River from Bismarck. That’s important, Nichols adds, because in the case of organic matter, “You have something that’s less than 5 percent of the soil, but it controls 90 percent of the functions.”

Brown came to his own realization that he could have a positive impact on organic matter somewhat by accident. He and his wife Shelly bought their farm from her parents in 1991, and in 1994 they went 100 percent no-till as a way to save moisture in their cropping system, which produced mostly small grains like wheat. Brown liked the no-till system, but bad weather produced a string of crop failures during the late 1990s.

It made things extremely difficult financially, to the point where the Browns were having a hard time borrowing enough money to purchase fertilizer. This forced them to start planting more legumes such as field peas, triticale and hairy vetch that could fix nitrogen and provide more homegrown fertility while feeding their cattle herd.

“I was using cover crops but I didn’t really grasp soil health,” recalls Brown. What he did grasp was that his wheat often did better when planted into ground that had just produced a cover crop. His soil color and texture was improving, organic matter levels were rising and water seemed to infiltrate the soil profile, rather than simply running off.

“So we had four crop failures in a row, and I tell people today that was absolutely the best thing that could have happened to me and my family, although we didn’t think that at the time,” Brown says with a laugh as he guides his pickup past beef cattle grazing a cocktail mix of warm season cover crops.

Fuhrer and other soil conservation experts in the region were impressed with Brown’s results and began talking about ways of combining cover cropping, livestock impact and no-till agriculture in a way that soil quality could actually be improved, not just maintained at a high enough level to grow a stand of wheat. For Fuhrer, taking such proactive steps couldn’t have come at a better time—he had grown frustrated with applying practices that simply maintained the status quo, if that.

Diversity is strength

Frankly, cover crops are nothing new. Natural resource professionals have long promoted planting a soil-friendly crop like rye in the fall after corn or soybeans are harvested as a way to reduce erosion. Such cover crops are often seen as having no immediate economic value, making them a tough sell in row crop country.

But in Burleigh County, the cover cropping concept has been taken to whole new level, and farmers have begun to see them as an integral part of their long-term financial viability, as well as the land’s ecological health. Again, this breakthrough on cover crops came at failure’s doorstep.

In 2006 Fuhrer was examining eight different species of cover crops planted on test plots. In one plot each species had been planted as a monoculture, and the other plots contained various combinations: two-way mix, three-way, etc., all the way up to where all eight species were planted together.

“And then we had one of the driest years on record,” recalls Fuhrer. “And then I just thought, oh, everything’s failed and we’re just not going to learn anything this year. And I was so wrong.”

What Fuhrer and his colleagues learned was that the monocultures failed, and the mixes involving just a few species didn’t fare much better. But the eight-way mixture didn’t seem drought stressed at all, and in fact yielded quite well.

“It really taught us a lot from the viewpoint of how plants won’t necessarily compete with each other—they can actually help each other,” says Fuhrer.

Minnesota ecologists have found that in planted prairies, greater diversity resulted in a similar synergistic effect—making the entire system more resilient. Fuhrer and his colleagues started thinking that maybe it was a lack of carbon below the soil that was the problem. The difference between soil and dirt is soil produces life, and it can do that because it contains carbon. And socking away that carbon for a rainy day (or a very dry one) pays big dividends.

Those eight species of plants growing above ground may appear to be in competition, but all the while they are creating an incredibly diverse subterranean ecosystem. Soil scientists say a diverse root system can create a soil that is resilient, less erosion prone and able to develop its own fertility.

“We figured out we wanted to stimulate soil biology through nutrient cycling and through roots,” says Brown. “Well, let’s have something really diverse and try it.”

These days most of Brown’s cover crop mixes contain as many as 20 species. The goal is to keep the soil covered and spider-webbed with roots year-round, and to extend the subsoil’s active biological season as long as possible—the greater variety of species above ground, the greater diversity of species below ground. In a typical year, Brown will do this by planting four crop types: warm season broadleafs such as alfalfa, buckwheat, chick pea, cowpea and sunflower; warm season grasses such as corn, millet, sorghum and Sudan; cool season grasses such as barley, oats and triticale; and cool season broadleafs such as canola, flax, vetch and sweet clover.

A growing season may consist of Brown planting winter wheat, harvesting it in June or July and planting a cocktail mix of warm season crops. Once they’ve grown up by late summer, these crops can be grazed well into the fall and even into early winter, producing good cash flow through the animals. The manure and urine deposited by the cattle, plus the trampling they execute while browsing, builds nutrients and carbon in the soil while supercharging biological activity, providing the basis for planting another cash crop like corn the following spring.

What must be kept in mind is that this isn’t strictly a no-till system, or strictly a grazing system. No-till—planting crops in ground that’s been disturbed as little as possible—is better for the soil than heavy tillage, but it doesn’t take full advantage of the nutrients and biological activity present deep in the soil profile, says Brown. He points out that the neighbor’s soil that’s lower in organic matter than his has actually been under a no-till regime since the late 1990s.

And grazing perennial grasses, again a more soil-friendly system when compared to tillage, isn’t the final word. Hal Weiser, a soil health specialist with the North Dakota NRCS, estimates that some of the season-long grazed land in the area has water infiltration rates of only a quarter inch. “Which is simply unacceptable,” he says.

Several years ago farmers in the region began switching from simply turning cattle out into large pastures for the entire season, to breaking them up into rotated paddocks. This provided extended rest periods for grass, and pastures responded with healthier stands that provided forage longer.

But more recently livestock producers have taken that rotational grazing concept one step further by utilizing mob grazing—a system where a lot of animals are placed in a paddock for sometimes only a few hours. The animals browse the most palatable part of the plants and generate a lot of biological activity, but don’t compact the soil. This system comes with the assumption that the cattle won’t make the most efficient use of all the forage—in fact they may trample a good amount of it, which is not only acceptable, but may be preferable in some cases. All that trampling just puts carbon underground and generates biological activity, in effect feeding the soil.

Making soil the focus

Nichols says the key to this system is accepting that soil is at the center of one’s farming system—not just another input that can be plugged in. That “dirt” is much more complex than we once thought is becoming increasingly evident as new advances in electron microscopes (thanks to medical technology) and DNA testing offer unprecedented glimpses into this fascinating world. But Nichols points out that in a way soil is a “big black box” that’s just becoming “blacker” as science churns up new information about what goes on beneath our feet.

“The chemistry happens the way the chemistry happens. But when you throw biology into the mix, it gets complicated,” she says while flashing microscopic images of soil organisms on her computer. “In some ways it’s a step backwards—we thought we knew 10 percent of the organisms in soil, now we realize it’s less than 1 percent.”

But that may not necessarily be a bad thing. It’s when farmers begin seeing soil as the heart of an extremely complex, oftentimes mysterious, system that they can start taking steps to get at the problem, rather than just treating the symptoms.

Nichols, who grew up on a southwest Minnesota crop farm, says a prime example of treating symptoms without getting at the core of the problem is what’s happening in the Minnesota River Valley with erosion. There are indications that field-level erosion in the Valley has gone down, thanks to the adoption of conservation farming techniques, among other things. However, studies show that sedimentation of the river continues at an alarming rate.

“What is going on with the soil now where we can’t get the infiltration of water?” Nichols asks. “We addressed some of the symptoms, which was great, but did we address the bottom line?”

An example of the bottom line being addressed is when microorganisms do something called “habitat engineering,” which has huge implications for not only cutting erosion, but also making sure soil can cook up its own fertility while staying in place. When soil does not have good aeration and plenty of pore space, it loses its ability to stick together and form strong aggregates.

“The water coming in can actually cause these aggregates to explode with air pressure,” says Nichols of a typical soil erosion situation in compacted soils.

But soils with more carbon feed themselves, and extra “food” goes into developing a waxy glue that holds aggregates together, creating a habitat where water can’t build up explosive pressure.

“They’ve actually engineered an environment that’s safe, that has food and has the ability to produce carbon to self-perpetuate,” she says. “The more of these aggregates there are, and the larger they are, the less susceptible to erosion the soil is. We’ve found management can impact this.”

Investing in the soil bank

Being able to improve soil’s ability to engineer its own healthy environment has huge implications on and off the farm.

Soil provides at least $1.5 trillion in services worldwide annually, according to the journal Nature. For example, soil stockpiles 1,500 gigatonnes of carbon, more than the Earth’s atmosphere and all the plants on the planet. And it’s the organic matter that does the heavy lifting: it can hold 10 to 1,000 times more water and nutrients than the same amount of soil minerals.

In recent decades, great strides have been made in reducing soil erosion to “T”, or “tolerable” loss rates—that’s the rate at which soil can be lost and still replaced. This is thanks to conservation tillage and structures such as grassed waterways and terraces.

But it’s become clear even bigger strides in conservation could be made by increasing soil carbon content, or managing for “C.” One NRCS estimate is that if all of our country’s cropland was managed for T, soil erosion would decline by 0.85 billion tons annually. If cropland was managed in such a way that C was increased, erosion levels would drop by 1.29 billion tons per year. In financial terms, managing for T is worth $16.5 billion annually; managing for C almost $25 billion per year.

But the health of soil on an international or even national level means little unless those dollars can come home to roost on the farm.

Brown says in his case, they already have. He farms around 5,400 acres—1,300 of that is cropland and most of the rest is pasture. The Browns own about 1,400 acres and rent the rest, so maintaining a regular cash flow is important. The main cash crops are corn, spring wheat, triticale and vetch. They run 400 cow-calf pairs and anywhere from 300 to 800 yearlings, depending on the year

Increasing organic matter on his farm has allowed Brown to reduce the use of commercial fertilizer by over 90 percent, and herbicides by 75 percent, and that’s paying off big time. Sitting on a four-wheeler near one of his corn fields, Brown shows a printout that outlines the financials for his 2011 crop. At today’s fertilizer prices, each 1 percent of organic matter contains $751 worth of nitrogen, phosphorous, potassium, sulfur and carbon, he estimates. That means Brown’s 5 percent organic matter content is worth $3,775 per acre. When he figures in his expenses for the 2011 corn crop—seed, herbicide, planting, storage, etc.—his 2011 return to labor, management and land was $5.38 per bushel of corn.

A long-term study done in Iowa recently showed that increasing diversity in cropping systems significantly reduced a farm’s reliance on fossil fuels and chemicals without sacrificing profits.

Still, cover crops and grazing aren’t attractive to producers farming high-priced land and gunning for bin-busting yields.

“There’s such an emphasis on yield and unfortunately with a lot of these systems, there is not an increase in yield,” says Nichols of soil building farming techniques. “But if you can afford to buy an input, then you can afford the cover crop seed or the yield drag. You have to look at your goals: yield or long-term viability?”

Brown says he sees planting cover crops and letting cattle graze/trample them as no different than forward-pricing his fertilizer. But he concedes that in these days of record corn prices, planting a cocktail mix of forages, many of which will end up as worm food, may appear financially foolish.

“And now we’re going to mob graze this with cow-calf pairs probably starting next week,” he says while standing in a former Conservation Reserve Program field he is renting. It was planted to some 20 species of warm season plants on July 20; on this day in early September, the crop is up to his chest. “I’ve got to pay cropland rate on it but I’m going to seed it back to native grasses next year. Everybody thinks I’m crazy seeding good cropland back to native grass but that’s what we want to do. To us, the resource comes first. The cattle can still gain on this and we’re still making money.”

Given the great strides he and other farmers have made in building soil health while improving profitability, Brown is a little perplexed that more producers aren’t focusing on treating the problem, rather than the symptoms. Some of the hesitation may be the result of the “inputs in-results out” model of agriculture that predominates.

Invariably, when Nichols talks to farmers about how fungi can improve soil quality, someone will ask, “Where can I buy them?”

“We are in the mindset that we can always go out and buy something to fix a problem, which may not be a problem, but a symptom,” says Nichols.

Brown says government programs like federal crop insurance don’t help matters any, since in many ways they reward farmers for raising crops in a way that is risky, but not sustainable. Remember: he credits failure for pulling his operation out of its monocultural rut.

“Adversity drives change,” he says.

Without that adversity, farmers aren’t forced to take a closer look at whether their system is just a series of reactions to symptoms, or whether it’s getting at the root of the problem. And without such a reexamination of systems, the true potential of soil, land and farms may never be reached.

“Gabe did something I thought was impossible and instead of telling him, ‘Good job,’ I said, ‘What more can you do?’ ” Nichols says. “I don’t know how far we can take it, but I like the idea of not putting limitations or constraints on a system. Can we take it a little further?”

Read part 2 of “Teaming With Soil Microbes” here.

To listen to an LSP podcast featuring members of the Burleigh County Soil Health Team click here.

Leave a Reply

  • (will not be published)