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Limit Physical Disturbances for Soil Health

“We need to cut back on tillage,” says Jill Clapperton, principal scientist with Rhizoterra, Inc., a Spokane, Washington, soil health firm. “Everywhere in the world, we need to reduce the amount of tillage. We need to reduce the amount of habitat destruction.”

Tillage reduces the soils’ capacity to function and causes bacteria to consume soil carbon, explains Ray Archuleta, a Natural Resources Conservation Services (NRCS) conservation agronomist in Greensboro, North Carolina. It adds an additional stressor to the system.

Besides wreaking havoc on the natural cycle, tillage causes you to lose soil at a faster rate than you would with no-till. Don Reicosky, a retired USDA-ARS soil scientist from Morris, Minnesota, cites a 1993 University of Kentucky study that compared conservation tillage with a conventional tillage system.

“On a relative basis, the conventionally tilled system lost soil 52 times more than a no-till system,” says Reicosky. “That was unacceptable. We are losing soil much faster than Mother Nature is making it.”

Reicosky says that is not a sustainable system, and more extreme climate can fuel soil erosion, like those 5- to 6-inch rapid rainfalls.

“No-till has an advantage in that the small amount of erosion that is lost is equal to the rate of soil formation. This will allow for the soil to be sustainable for five to 10 future generations,” he says.

What’s your soil’s most limiting factor? Nitrogen, right? Maybe potassium? How about phosphorus?

Wrong, wrong, and wrong again. Carbon is the most limiting factor in the soil.
Surprised? Don’t be. “Carbon is the energy substrate that drives the soil. Organic matter is about 58% carbon. It runs the system,” says Archuleta.

“Carbon is important in all soil activities,” adds Reicosky. “Carbon impacts the soil structure and nutrient cycling. Carbon is important to maintain the physical, chemical, and biological processes in the soil. That makes carbon the greatest management tool available.”

“We haul it off, we till it, we bale it, it goes off as carbon dioxide,” adds Archuleta. “If we incorporate residue, how much of it actually makes it into the soil? Only 35%. The rest of it goes off as carbon dioxide.”

All this leaves soils carbon-depleted, he points out.

“Carbon input through plants nurtures bugs that chew up biomass in roots, shoots, and leaves. Biomass provides and recycles nutrients. Carbon also helps cycle nutrients. Building up carbon in the soil enhances water-holding capacity,” says Reicosky.

Carbon keeps the soil pores open and facilitates the water cycle. The water cycle isn’t complete until it goes into the soil system. All of these systems are connected intimately, says Archuleta.

No-till paired with cover crops makes all the difference. These carbon-retention twins help retain soil carbon nearly year-round. Without some form of energy that soil carbon can help fuel, soil biology will not function.

“By using no-till and cover crop mixes, you can work with nature’s diversity and synergy to manage carbon in order to achieve better lifestyle for food security,” Reicosky says. "With no-till, you have minimum carbon loss. With cover crops, you maximize carbon input in regard to carbon management. Without good carbon management, you will not have a sustainable system."

Soil residue helps protect the soil surface. “This decreases evaporation, so there is less water wasted and more going to the plant,” Reicosky says.

If you can manage soil carbon better, there will be food security for future generations, says Reicosky.  

The takeaway? Leave crop residue alone.

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