Dirt clods, mud pies and other insights in soil sustainability

Like most farmers, Doug Peterson’s concepts about farming and soil management were founded on the experiences and teachings of his father and grandfather. The knowledge they imparted was taken as gospel truth, inviolable and immutable. A college degree reinforced those ideas, and a career as an Natural Resources Conservation Service field specialist let him put those ideas to work.

By his 20th year on the job, he felt he knew about everything there was to know about soil—how to use it, how to take care of it, how to improve it.

He was on top of his game. Which was why, when he was asked to evaluate a workshop on soil health for possible inclusion in Missouri NRCS programs 10 years ago, he attended with some skepticism. “What else could it teach me?” he wondered, and sat there in utter disbelief as the instructor, using dirt clods and mud pies to illustrate complex biological processes, methodically and systematically dismantled his understanding of soil.

Everything Peterson thought he knew about soil was based on a world that no longer existed. Since the first farmer broke the soil in Mesopotamia 20,000 years ago, an unimaginable transformation had altered not only societies and cultures but the very fabric of existence of life on earth. Nothing was spared, not the air, not the water, not the soil.

So revelatory was that simple demonstration that Peterson, an NRCS soil health specialist for Missouri and Iowa, now uses it as an opening act for his Soil Health Sustainability in Cropland workshops. Joining him for five such workshops across Kansas in mid-July was Candy Thomas, NRCS Soil Health Specialist for Kansas and Nebraska. The workshops were sponsored in part by the Kansas Alliance for Wetlands and Streams through funding by the North Central Extension Risk Management Education Center and the USDA National Institute of Food and Agriculture. Locations included Iola, Parsons, Clay Center, Stull and Lansing.

Peterson, like most farmers and soil specialists, wasn’t blind. Most of his work dealt with mitigating changes in the soil, in the water, in the climate, but the changes were both resistant and resilient. They could also be oddly contradictory, such as when the Missouri River flooded while two-thirds of the river’s watershed were in drought. Farmers were losing ground, literally and figuratively, and conventional farming practices only seemed to make matters worse.

Whatever underlying causes were wrecking such havoc had to be related to the water cycle, he thought. “If you have flood warnings and drought conditions in the watershed at the same time, how much infiltration is occurring? Not much,” he said. “And we’re not talking 15-inch rains, but three-inch rains that cause flooding like we’ve never seen before. We have to understand water.”

More specifically, we have to understand how water interacts with soil. Peterson took two virtually identical dirt clods, or aggregates as he preferred, and placed them in a matching pair of glass beakers. As he poured water over them to replicate a heavy rainfall, one clod, taken from a field where no-till was practiced, retained its shape while allowing most of the water to filter through; the other, taken from a field under long-term tillage, disintegrated within seconds.

“The most limiting natural resource in crop production is water,” he said, “and the most important part of the water cycle is infiltration. It’s critical to understand how the ability of soil to hold together impacts infiltration.”

The no-till aggregate was held together by organic matter and soil organisms such as fungi, arthropods, worms, millipedes, bacteria, nematodes and protozoa, he said, while the other had little more than sand, silt and clay to bind it.

For infiltration purposes, the most important part of the soil is the nothingness, the cracks, the voids, he said. Water cannot pass through solids. In no-till fields, rain slowly percolates through root channels, cracks, wormholes and other minute openings, while in tilled fields the upper layer of topsoil has little organic matter to glue it together. The entire structure can collapse during even moderate rain events.

“Erosion doesn’t start with a big chunk washing away,” he said. “It starts when individual particles break loose from the aggregate.”

In healthy soil, the combined biomass of soil organisms is staggering. An acre of soil contains more than five tons of organisms such as fungi, arthropods, worms, millipedes, bacteria, nematodes and protozoa, many of them microscopic. Earthworms mix and move residues in the soil, creating large pores that are nutrient rich and filled with microbes. These pores create air and water flow and allow roots to grow and take advantage of resources.

“Pore spaces are the lungs and circulatory system of soils,” Thomas said. “They allow the soil to breathe.”

Not so with soil that’s been tilled. Studies show that long-term tillage drastically reduces soil organic matter. One study conducted in a soybean field showed a 63 percent loss of soil organic matter after 17 years of tillage.

Much of that loss can be attributed to disturbance. Tillage adds oxygen to the soil, which in turn induces bacteria to consume carbon. Half to two-thirds of our soil’s carbon has been lost through tillage, Peterson said. Surface temperatures play a critical role in soil organisms, too, especially in grass systems.

“When we mow hay off on the sunniest days, we jack up soil temperatures 40 degrees or more,” he said. “What happens to soil moisture? We eliminate it. Earthworms go deep, but most of bacteria and the fungi will grow dormant or die.”

Add fertilizers, pesticides and herbicides to the mix and even more damage occurs.

Why then, Peterson asked, if we know that tillage degrades the soil, why is it so ingrained in our society?

Because it was efficient. Whether the first farmers broke the soil in Mesopotamia or, 4,000 years later, in the Midwest, the underlying soil teemed with life. “It had crazy high organic matter, high biological activity, high aggregate stability,” Peterson said. “But after years of tillage, what happened to organic matter? It declined. What happened to aggregate stability? It went down. What happened to production? It went down.”

For early farmers, their only recourse was to break new ground and allow the old ground revegetate. A similar pattern took place in the United States, he said. Settlers tilled areas for crops and left grassland for their livestock. Once the soil became less fertile, they rotated to other sections while the land healed. Then came the 1940s and mechanized equipment. Suddenly, farmers didn’t need extra land to regenerate. They added nitrogen, phosphorus and potassium to the soil and called it good—but they didn’t put back organic matter.

“The reason we’ve been taught that tillage is beneficial is because historically, except for the last 50 or 60 years, it was based on soils with high organic matter, biological activity and aggregate stability,” Peterson said. “Is that the kind of soil we have these days? No. Tillage doesn’t get you the kind of soil that we once had.”

Add overgrazing, overuse of pesticides and herbicides, haying and other sources of soil disturbance, and it seems as if we’re actively trying to get rid of water, he said.

It’s not too late to restore the ecological balance, Peterson said, but it won’t happen overnight and it won’t be easy.

“Change is hard,” he said. People make changes when their backs are against the wall. If you think it’s hard for a farmer to change from tilling to no-till, how much harder is it for the government to change everything its practices are based on?”

Achieving soil health requires utilizing a number of practices that include the use of diverse and strategic cover crops, crop rotations, adapted nutrient management, integrated weed and pest management, and no-till. “Soil health is not a destination, it’s a journey,” he said. “Managing for a living ecosystem is the key to optimum production.”

From a resource concern standpoint, producers should design for what they don’t have. “What does your soil need? Get your shovel out and start digging,” he said. Crop diversity cannot be ignored or overstated. Plants were created to grow in diverse ecosystems. Nature doesn’t have a monoculture.

“If we put these principles to work, we can make huge changes in our fields,” Peterson said. “The last 100 years have been a mining operation. We mined organic matter just like they mined oil and minerals. It was an extraction operation, and all of us are left with something less productive than it was. But we can change it. We have the answer right here. We can improve production and profitability and solve all the issues. We can’t hit the easy button as Candy said, but we can push the start button.”

Funding for the workshops was provided by the North Central Extension Risk Management Education Center and the USDA National Institute of Food and Agriculture. Project partners include the Kansas Alliance for Wetlands and Streams, NRCS-Kansas, Kansas Water Office, K-State University, Kansas SARE, No Till on the Plains, Kansas Dept. of Health and Environment, nine Watershed Restoration and Protection Strategy groups, Kansas Grazing Land Coalition and Friends of the Kaw.