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Facing carbon credits

By Staff | Mar 5, 2010

No matter how proposed climate-change legislation fares in Congress, carbon likely has more value than what it trades for, especially for farmers. Production practices that capture carbon can make economic sense whether or not the legislation passes, according to Jerry Hatfield, director of the National Laboratory for Agriculture and Environment at Iowa State University.

“Too often producers think, ‘If carbon is worth a certain price, then I’ll adopt certain practices.’

“But in reality, the carbon in your soils already has value. It’s very exciting to consider how much we can improve production efficiencies by changing the soil’s organic matter content.”

Increasing levels of organic matter is a form of carbon sequestration. Even though carbon is a small part of the soil, it’s a critical component for soil water holding capacity, nutrient cycling and more, Hatfield said. “Our agricultural systems are limited by water more than anything else. The more organic matter you have, the more available water content you have in the soil, and high plant yields are dependent on high levels of available water.”

The organic matter (including roots, microorganisms and humus) of soil can vary widely, however. Many soils in the United States have less than 1 percent organic matter, although it’s closer to 3, 4 or 5 percent in many parts of the Midwest.

The remainder of the soil volume includes air (25 percent), water (25 percent) and mineral particles (45 percent).

What’s organic matter worth? According to research conducted in Iowa, a 1 percent change in organic matter, which includes roots, microorganisms and humus, across a field, represents a change in corn yields from 16 bushels per acre up to 40 bushels an acre, due to increased water availability, Hatfield said.

More carbon and organic matter also provide a host of other environmental benefits, including reduced soil erosion, less runoff, improved water quality, improved soil tilth and structure, reduced fertilizer inputs and more, he added.

Boosting soil matter

There were three agricultural practices that Hatfield recommended for sequester carbon and improving soil organic matter. These included:

  • Reduced tillage. “Improving carbon sequestration within the soil will require a change in tillage practices, because that’s ultimately where we lose a lot of our carbon,” Hatfield said. “Even if you can’t go no-till in your area, you have options.”

Since much of the organic matter that builds in the soil comes from old root systems, strip-tillage can help preserve organic matter.

“If you have corn in 30-inch rows, for example, don’t till right over the top of the rows,” Hatfield said. “Split the middles with some sort of strip-tillage system, leave the old root system there, and plant between it. By offsetting the rows 15 inches and planting right over that, we’ve seen pretty good results.”

Strip-till systems can begin to accrue organic matter in the upper surface of the soil within the first couple years, and the long-term benefits become evident within five years.

  • Cover crops. These provide a number of benefits. In addition to taking carbon out of the atmosphere and putting it back in the soil, cover crops also promote a healthy biological system within the soil, which helps accrue organic matter faster in the soil, Hatfield said.
  • Crop rotations. Hatfield noted that diverse crop rotations change the time of the year when carbon is being removed from the air and put in the soil.

Although the whole carbon market structure is in a state of flux, and no one is certain what role agriculture will play in this, Hatfield said producers can tap into a variety of resources to sequester more carbon while improving their production efficiency and profitability.

Options include the Natural Resources Conservation Service, district conservationists and the local Extension service. Farmers can also contact the National Laboratory for Agriculture and Environment if they have questions, he added.

“The value of carbon goes beyond $10 or $20 per ton, because more efficient crop production is priceless in terms of what we can do.

“Agriculture needs to look at the impact of increasing carbon within our soils to sustain the agricultural revolution required to feed the world. To do this, we need to look at the integrated picture of water, carbon, light and nutrients to optimize production.”

You can contact Darcy Dougherty Maulsby at yettergirl@yahoo.com.

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