WHEATLAND — Area farmers and ranchers enjoyed a rangeland soil health workshop/tour Aug. 22 that imparted the most sophisticated understanding of soil currently available to science, which now compels many to explore agricultural techniques that minimize disturbance of the soil.
A tour of local ranches, the Mount and Goertz ranches, took up the afternoon following a morning of classroom-type instruction at Platte Valley Bank presented by Marlon Winger, with the U.S. Department of Agriculture Natural Resources Conservation Service, on five principles of soil health; Dr. Peter Stahl, of the University of Wyoming Department of Ecosystem Science and Management, on soil microbiology and the implications for soil health; and Stan Boltz, with NRCS, on soil health, forage quality/quantity and livestock production.
Plowing not that great
Winger said the five “eternal” principles of good soil health are:
Minimize disturbance.
Maximize soil armor.
Maximize biodiversity of plants in the crop rotation.
Keep living roots in the soil as much as possible — don’t leave a field fallow.
Integrate livestock into the crop system.
Winger began with a slate test, which he explained is to test the internal strength of a dirt clod. Clumps of soil are placed in the top end of tubes of water to demonstrate how quickly they dissolve. Regularly plowed soil has almost no cohesion, dissolving like a sugar clump and readily falling through the screen to the bottom of the water tube in a fine cascade, while aggregate soil that has not been so disturbed keeps its clump in the top of the tube much longer. When it does at last break apart, the aggregate soil produces no fine cascade of silt, only smaller aggregate clumps that drop to the bottom.
Winger said when he was growing up, the understanding was the more you plow it, the better the soil is. However, he said, now science shows that the more plowing is done, the more the soil ecosystem is destroyed.
“It’s like building a beautiful house, or the bank,” Winger said. “We got all this pore space, all this room to live in — a kitchen and a bathroom and a vault. But if a guy bulldozes it three times a year, we still have the same structure, but there’s no pore space. There’s no place to live in, a habitat.”
Winger said microbes in the soil eat each other and release biological glues that cement soil particles together to make aggregate.
Winger also stressed the importance of mycorrhizal fungus, which has a symbiotic relationship with plant roots, as well as releases protein called glomalin that holds soil aggregate together. He compared the glomalin to the scene in “Ghostbusters” when a ghost covered the characters in slime.
“They’re all just boogered, right?” Winger said. “That’s the biological world. They’re all releasing these goos, and with an electron microscope now we can even start seeing some of these goos being released.”
Winger said mycorrhizal fungus doesn’t get its own carbon but has to get carbon from plant roots. The fungus also spreads far beyond the root system and brings nutrients and water back for the plant.
Winger presented on protozoa and other “critters” that live in the micro-aggregate, or pore space, of healthy soil. Mites, bacteria-eating nematodes and more populate the pore space and contribute to the soil ecosystem.
“This is how soil functions,” Winger said, to chuckles, as he sprayed Silly String all over a pile of clutter he was using to illustrate the different components of healthy soil.
He then smashed the pile of clutter to demonstrate how plowing destroys the soil ecosystem, smashing the microbes’ tiny homes and causing the soil to lose horrendous amounts of carbon dioxide. He said soil ecosystems are resilient and can be rebuilt, but the challenge in the West is that soils here are particularly fragile.
Winger said healthy soil functions as a viable living ecosystem that sustains plants and animals. He said he has always advocated sustainability in agriculture, but what he once thought were good soil management techniques are actually destroying the soil.
“I’m almost sick to my stomach and my heart to think most of what we’re farming in America is ‘sustainable.’ I’m just sorry,” Winger said. “I thought we were, but I’m changing my mind very quickly.
“We’re not even close to sustainable systems. We have to think of restorative systems … if you think you have a sustainable nutrient cycle, just look at your fertilizer bills.”
Winger said he knows of some farmers who have taken up strip-till or no-till techniques, and by doing so have developed such good nutrient cycling on their lands that they haven’t applied fertilizers for a decade.
Winger showed some slides of dust blowing in Idaho, Oklahoma and other places because of bare fields. He said a field in fallow is in starvation mode, and the more soil is tilled, the more carbon it loses. He said the U.S. has lost half the organic matter in its agricultural soil during his generation alone.
“Our soil is in trouble — we didn’t learn anything from the 1930s,” Winger said.
Stahl added the Dust Bowl of the 1930s, the worst soil erosion disaster in history, had little to do with the weather and much to do with poor soil management. He noted most soil erosion in Wyoming is due to wind blowing over bare ground, blowing away layers rich in humic acid.
“The same thing that makes scotch taste so good — humic acid — also turns the soil that dark color,” Stahl said.
Winger said soil is seldom disturbed naturally; most natural soil disturbance is catastrophic and rare, such as earthquakes.
In addition to wind blowing it away, water also washes bare soil away. Winger pointed out that aggregate soils do not have a runoff problem, which is actually a water infiltration problem. He illustrated the point with a rainfall simulator later at the Mount ranch during a demonstration that showed how much water runs off versus soaks in to the different soil types. Conventional tilled soil soil and continuously grazed soil had the worst results, with much more water running off the top than soaking in — and carrying soil away with it.
Winger urged everyone to keep living roots in the soil as much as possible, as well as maximize the diversity of plants in their crop rotation to benefit the soil’s resiliency.
Microbes are great
Stahl said much more is happening unseen underground than above ground where plant growth is observed. He said most microbes in the soil get their energy from plant roots, and they provide benefits to the plants in turn. However, he said, if livestock grazes off too much ground cover, it won’t leave enough leaf to photosynthesize nutrients for what’s happening below ground.
Stahl strongly recommended “graze half, leave half” because to defoliate over half the leaf volume dramatically diminishes root growth. Removing up to 40 percent of leaf volume will not stop root growth at all, but removing 50 percent will stop about 2-4 percent root growth. More than that, however, has a huge impact — removing 60 percent of leaf volume halts 50 percent of growth.
Stahl said a square meter of soil contains over 10,000 species of bacteria and fungi, most of which cannot be grown in a laboratory. He said Wyoming has about 2,000 native plant species.
“There are a lot more species of bacteria in just a handful of soil than all the plant species in the state,” Stahl said.
He noted any healthy person has a couple pounds of bacteria in their body assisting bodily functions. He said people depend on bacteria, which perform many different functions, as much as they depend on plants and soil. Stahl said algae also live in soils, mainly near the surface where they can get sunlight. He said tons of insects and arthropods also live in the soil, and all their biological secretions act as glue to hold together the soil aggregate.
Stahl said good healthy aggregate soil contains about 50 percent air space and 50 percent solids. He said sandy soils contain less air space. He explained some aggregate chunks contain no oxygen, therefore no nutrients held within the clump will decompose. He said if the aggregate structure is torn apart by frequent tilling, the organic matter loses its protection and decomposes.
Weeds are not that bad
Boltz was also against conventional tilling methods, which he said are not conducive for maintaining nitrites in the soil. He said the water infiltration rate of soil is determined by the plant community living in it and how the soil is managed. He explained how much better water infiltration happens in aggregate soil as opposed to soil that is often disturbed.
Boltz said properly managed grazing benefits the soil, but too much destroys it. He advised ranchers to graze half their forage and leave half to conserve soil’s organic carbon. He also stressed the importance of keeping the soil covered with plants, although too much litter on the ground can sometimes slow the nutrient cycle.
“Weed control should be a last resort,” Boltz advised.
Boltz said many weeds contain good stores of protein for grazing livestock.
Boltz said the keys to good grazing lie in proper stocking, adequate recovery periods for the soil, changing seasons of use and striving for year-round grazing.
At Dallas Mount’s ranch west of Wheatland, where another slate test and the water runoff demonstrations were set up, Boltz grabbed a handful of rich, dark, clumpy aggregate soil that he held up for everyone to see.
“This is the structure you want— like cottage cheese or chocolate cake,” Boltz said.
Boltz said no-till alone will not solve agriculture’s soil problems; producers must also consider their grazing cycles.
