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Reducing greenhouse gases through soil stewardship

BY KARIN DENEKE

Carbon sequestration was not yet a part of my vocabulary when we decided to give no-till a try in 1985 on our recently purchased farm ground in southwest Ohio — ground that had been over plowed, under managed and leaking carbon.


The local Soil and Water Conservation District (SWCD) had recently purchased a no-till drill, a tool available for farmers to test conservation tillage — a new alternative planting method that saved soil and reduced time in the field. It was also a push to retire the moldboard plow. Many farmers of the older generation did not readily trust this newfangled planter. For decades, moldboard plowing was part of their planting regiment. Now they cautiously observed neighbors’ fields that had been converted to conservation tillage before they finally bought in.

Our farm is located in the Wisconsin Age glacial region of Ohio, where broad, gently rolling-hill plains with large areas of deep, fertile, mostly level soils are the norm. Our average annual rainfall is 36 inches — enough precipitation to support dry-land farming

In May of 1985, we took advantage of the no-till drill available from the local conservation district and planted twenty acres of soybeans into previous years’ corn stubble. Harvest was a success with a slightly higher yield than that of years past.

This marked the beginning of a new chapter for our farm operation. Improvements did not happen overnight — it was a steady but slow process. We observed that by not disturbing last year’s crop residue and by planting directly into it, the fields became less prone to soil erosion.

The major soil types on our land were Miamian (Mhb) and Crosby (CeB) silt loams. These soils have a moderate-deep root zone over glacial till. While the Miamian soil type had good drainage, the Crosby soil pockets had moderate permeability with a seasonal, high-water table. Thus we worked with our local SWCD to install grass waterways and other erosion control practices. In later years, cover crops were introduced to protect the soil and to add nutrients as it lay fallow.

As our soils improved, so did the yields. The farm produces field corn, soybeans and wheat on rotation, with some grass hay on steeper slopes. Minimum tillage helped trap or sequester carbon in the soil. By avoiding deep tillage, we gained soil organic matter, resulting in a healthier soil.

What exactly is soil carbon? When you view the periodic table in your old chemistry textbook, carbon is classified as a lightweight gas with an atomic weight of 12. As plants remove carbon dioxide from the atmosphere through photosynthesis, some of this gas is stored in their foliage along with the other greenhouse gas — nitrogen. When carbon is fixed in the soil, the result is a more fertile seedbed. Moldboard plowing on the other hand rips open the soil and allows large amounts of carbon dioxide to escape into the atmosphere.

In the year 1997, I had the opportunity to witness a demonstration showing how greenhouse gases are released during moldboard plowing while visiting the North Central Soil Conservation Research Lab in Morris, Minnesota, now renamed the USDA-ARS North Central Soils Lab. It is the lab where renowned soil scientist Dr. Don Reicosky researches CO2 flux from different tillage methods. At that time, I had joined the staff of the Miami SWCD — our local conservation district in Ohio — and traveled with Barb Francis, member of our board of supervisors, and her husband Bob, to Morris, Minnesota. Barb and Bob practiced no-till on their farm, and Barb was a serious advocate of soil health and carbon sequestration. Following our return from the research lab, Barb went on the speaker circuit to promote conservation tillage. As a result, in the year 2008, Barb was inducted into the Ohio Federation of Soil and Water Conservation Districts Supervisors Hall of Fame. 

Dr. Reicosky’s research in the field included a mobile laboratory housing gas analysis equipment, which among other things could measure and later compare the gaseous losses of various tillage methods. The machine, called MR.GEM, was equipped with a screen that graphed the escaping flux released during moldboard plowing, allowing us to watch the data while the device moved across a sod-covered field.

We could not help but notice the dark, deep, rich soils of the region, an area once covered by Tall Grass Prairie. This vegetation had massive roots, roots that were three times longer than the plants above the surface — thus creating a robust network of decaying organic matter

During the early 19th century, wagon trains pushed westward to start settlements, thus the prairie was attacked by the plow with a vengeance. As a result, just three percent of North America’s Tall Grass Prairie remains today. The state of Minnesota once had 18 million acres of prairie stretched across the state. Just imagine this massive carbon sink.

According to Rattan Lal, director of the OSU Carbon Management and Sequestration Center, “The world’s cultivated soils have lost between 50-70 percent of their original carbon stock — much of which has oxidized upon exposure to become CO2.”

Studies are underway to learn how land restoration in places like the North American Prairie, the North China Plain and the interior of Australia may help put carbon back into the soil.

The USDA-NRCS Soil Survey remains an important resource for farmers, ranchers and land users. It not only lists and maps the different soils in a given area, but also addresses in detail the use and management of soils. It reviews soil properties such as shrink and swell potentials of certain clays — which is important when it comes to construction of house foundations — and describes flood plain soils and drainage potentials.

The soils in every county in every state have been surveyed by soil scientists from the Natural Resources Conservation Service (NRCS), formerly called the Soil Conservation Service (SCS). It was a tremendous effort that continued for decades. My old hard copy was issued in 1978 and is no longer available. Instead, the United States Department of Agriculture Natural Resources Conservation Service upgraded to the Web Soil Survey. It provides a simple, yet comprehensive way to access soil data in three basic steps (websoilsurvey.nrcs.usda.gov).

When Franklin Delano Roosevelt was sworn into office in 1933, the nation still suffered from the aftermath of the 1929 Stock Market Crash, while at the same time being threatened by a serious drought hitting the farmland of the Great Plains. FDR established the Soil Erosion Service in 1933 to address the ongoing devastating erosion issues. The agency’s mission was to introduce conservation practices to farmers and ranchers and to encourage soil stewardship.

In 1935 the Soil Erosion Service was renamed the Soil Conservation Service. Almost sixty years later in 1994, the agency underwent another name change –  it is now known as the Natural Resources Conservation Service (NRCS). Soil Conservation offices assisted by the NRCS are serving landowners in every county of every state.