When asked to look at a generic picture of farmland and pinpoint a problem, most attendees at this afternoon's Idaho Environmental Forum
couldn't pick out what was wrong. The scenery showed gentle slopes of tilled soil and a creek with grass growing along it. Some guessed maybe the stream was eroding the land. Others thought there wasn't enough grass between the stream and the tilled soil.
"We have lived in a disruptive soil structure for so long, we can't even see what's wrong with it," said speaker Marlon Winger
, the state agronomist for the Natural Resources Conservation Service.
He said the the problem was the bare, tilled soil covering the land.
"That battle starts up there on the naked soil."
Winger spent the lunch hour explaining how Idaho's system of agriculture is leading to unhealthy soil. Idaho farmers rely almost entirely on heavy machinery to till their farmlands, but Winger said soil should be left undisturbed.
He brought a science class-looking demonstration to prove this. In the demonstration, he took two samples of the same soil—one that had been tilled often and one that had not—and let volunteers pop them into separate tubes of water. The first soil instantly turned the water an opaque brown. The second soil remained intact and the water, clear.
Then he performed another demonstration with the soil samples, where he poured water over the non-tilled soil and watched as the water quickly filtered and drained to the bottom. In the second, the water mostly settled on top, not seeping into the soil at all.
Winger explained that when soil doesn't get tilled, it leaves its natural ecosystem better intact. The fungi and bacteria and other organisms that live in the soil live off of decomposing plant matter, and create carbon, which helps plants grow. When the soil gets tilled, most of the carbon is released into the atmosphere as carbon dioxide and the soil is no longer as fertile.
"Conventionally tilled soil has no room for life," he said.
Having biodiversity in soil also creates pores throughout that trap and hold water, allowing for saturation. Tilled soil doesn't have nearly as many critters like earth worms to help create those pores.
Winger also said that when the soil is tilled and no longer stable, it becomes more susceptible to eroding and blowing away as dust. Sediment, especially when it's coated in phosphorous from fertilizers, is the number one pollutant to rivers and streams, he said.
"Agricultural soils don't have a water erosion and runoff problem. That's just a symptom," Winger said. "They have a water infiltration problem."
In his presentation, Winger talked about a farm outside if Marsing where he helped conduct an experiment. The farmers decided to leave their land untilled for three years. After that, they planted a cover crop to shade the ground and provide nutrients for the soil. Then they brought in 300 cows and let them eat the grassy crop—leaving manure behind as a natural fertilizer.
The soil ended up with 7.2 million earthworms per acre. That's 165 earthworms in one cubic foot, compared to the four to 10 one would usually find in a cubic foot of tilled soil, according to Winger.
"So will soil respond to good soil health practices?" he said. "Yes."
Winger said it's important for farmers around the state to think beyond sustainable farming and start thinking about "restorative farming." He stressed that after harvesting a potato crop, for example, farmers should immediately reseed a cover crop to protect and nourish the soil.
Not tilling the soil also saves money because it requires less water as soil gets better at absorbing the irrigation, and it skips expensive tilling machine operations. He said heathy soil is becoming more and more important in the arid west to conserve water. It's not exactly common yet, though.
"We are in the infancy of no-till systems," Winger said. "But those farms doing that—they are the innovators."