Boosting Topsoil Quality
Dan DeSutter asks a seemingly easy question: If you invested money with money managers who lost half of it, what would you do?
Easy answer: They’re outta there.
Swap money for soil carbon, though, and the answer is harder to face. That’s the U.S. soil carbon loss over the last 60 years, says the Attica, Indiana, farmer.
“Carbon is the key ingredient in soils,” adds Ray Archuleta, a Natural Resources Conservation Services (NRCS) conservation agronomist in Greensboro, North Carolina. “Soil organic matter is 58% carbon.”
Organic matter has a number of benefits, such as being a reservoir of nutrients and boosting water-holding capacity. Soil carbon holds the key to even more benefits.
“We can have soils with 10% organic matter that still don’t cycle water and nutrients,” says Archuleta. Instead, having active carbon is key. That’s because soil teems with thousands of living organisms, including soil microbes like bacteria and fungi.
Without active carbon in soils, it is like living in a mansion eating little cocktail wieners every night,” says Archuleta. “We have to feed the microbes (with active carbon). If you give them food, they release ammonium that can add 17 to 60 pounds (per acre) of nitrogen (N) to the crop.” These microbes also can spur release of nutrients like phosphorus and zinc to crops, he adds.
Of course, having the soil to retain carbon and organic matter comes first. There’s good news on that front. The latest USDA/NRCS National Resources Inventory shows cropland soil erosion decreased 41% from 1982 to 2010. Annual water erosion rates declined from 1.67 billion tons to 982 million tons during this time frame. Meanwhile, annual wind erosion losses dipped from 1.38 billion tons in 1982 to 740 million tons in 2010.
Still, maintaining a thin black line of topsoil that determines bounty or despair is challenging. Archuleta cites a Colorado dust storm that occurred in January 2014.
“I never thought we would experience a dust bowl, but we did,” he says. “The majority of our soils are degraded all over the planet. When I go to a farm, I assume soils are degraded unless I’m shown otherwise.”
|Soil Cores and their Characteristics
Next time you’re by a fence line, plunge a shovel into it. The loose, pliable soil permeating with microbial activity mimics the tallgrass prairie present before European settlers arrived.
“When the tallgrass and mixed-grass prairie was tilled, the oxygen it added increased the rate of organic matter decay,” says Dwayne Beck, manager of the Dakota Lakes Research Farm near Pierre, South Dakota. “When organic matter decreases, the ability of the soil to maintain good structure decreases. The porosity collapses, and the water-holding capacity of the soil decreases. The soil particles are too close together.”