It is a known fact that greenhouse gases, such as carbon dioxide and methane, are increasing every year in the earth's atmosphere. This buildup may well be leading to global warming.

Scientists say there are two main ways of reversing this trend: (1) reducing fossil fuel emissions, and (2) taking more carbon out of the atmosphere and storing it in natural "sinks" on earth, a process known as carbon sequestration.

Agriculture can help in both ways. With sufficient economic incentives, producers can use currently accepted management practices to help store more carbon and reduce emissions, and this will help the U.S. meet greenhouse gas reduction goals. This can be done on cropland, grazing land, and set-aside ground. It is estimated that up to 20% of U.S. carbon emissions can be sequestered back into agricultural soils.

Agricultural soils represent one of the best sinks for carbon storage in the Earth's ecosystem. Deep ocean storage and deep geological storage are other potential carbon sinks, but are more costly and less practical than using agricultural soils.

How can producers increase carbon storage in agricultural soils? This is being studied by a federally-funded team of scientists at 10 universities and government laboratories known as the Consortium for Agricultural Soils Mitigation of Greenhouse Gases (CASMGS, pronounced "chasms"). CASMGS brings together the nation's top researchers in the areas of soil carbon, greenhouse gas emission, conservation practices, computer modeling, and economic analysis.

With the current state of knowledge, it is known that carbon sequestration can be accomplished by the following means:

Cropland

1. No-till or reduced-till systems
2. Increased crop rotation intensity by eliminating summerfallow
3. Buffer strips
4. Conservation measures that reduce soil erosion
5. Using higher residue crops, such as corn, grain sorghum, and wheat
6. Using cover crops
7. Selecting for varieties and hybrids that store more carbon

Grazing land

1. Improving forage quality
2. Regular use of prescribed burning to increase forage productivity
3. Reducing overgrazing

Set-aside land

1. Growing high-yield grasses, such as switchgrass or eastern gamagrass on Conservation Reserve Program land .

Estimates of the carbon sequestration potential are available for some of these practices:

Agricultural practice                Amount sequestered (tons/acre/year)
Conservation tillage                          0.12-0.20
Summer fallow elimination                 0.05-0.15
Rotation with winter cover crops       0.05-0.15
Fertilizer management                        0.025-0.075
Conservation Reserve Program         0.15-0.35

Many of these practices involve additional costs for producers, and would require some financial incentives to implement on a wide-scale basis. Part of that cost could be accomplished through a private system of "carbon credit" trading. It is estimated that producers who implement one or more practices proven to store carbon in agricultural soils might be able to sell carbon credits to utilities and other industrial concerns for about $2 per acre per year on the open market. This type of trading system is in its infancy now, so there's no way to know how much producers can realistically expect to get from selling carbon credits.

Additional tax incentives or "green payments" from the government would probably be needed, especially for implementing practices with higher costs and limited returns. This would include such practices as buffer strips, most soil conservation measures, and the use of cover crops.

Other practices, such as no-till, increasing crop rotation intensity, manure application, and improved forage production, may be more profitable for producers in themselves. Where this is the case, the increased profitability will help get the practices implemented.

As an example, research at Kansas State University has shown that no-till grain sorghum in western Kansas is about $30 per acre more profitable than conventional-till grain sorghum. The profitability of wheat is largely unaffected by tillage system, according to the research. The biggest benefit in western and central Kansas comes when no-till is used in combination with increased rotation intensity. For example, a long-term study in Hays showed that wheat-sorghum-fallow is about $10 per acre more profitable than either wheat-fallow or sorghum-fallow. In eastern Kansas, no-till has not shown any increase in profitability in K-State research, so other economic incentives would be more important in this area to get farmers to adopt no-till.

The additional amount of carbon that can be stored in agricultural soils through the adoption of no-till and increased crop rotation intensity is estimated to be between 400-500 pounds of carbon per acre per year. Nationwide, this could total anywhere from 80 to 300 million tons per year.

No-till also involves less field work. By reducing the number of trips over the field from 8 to 4, carbon emissions would be reduced by 50%.

The amount of carbon that can be sequestered and the amount of emissions that can be reduced through the adoption of other potential practices, such as the use of buffer strips, requires further research.

If producers can be induced to adopt more practices that store carbon, there will be many benefits to the nation other than just helping to solve the problem of increasing greenhouse gases. Additional benefits include:

1. Improved soil structure and quality
2. Improved soil productivity through increased organic matter
3. Reduced erosion through improved soil structure
4. Improved water quality through reduced erosion

To sum up, changes in practices used on agricultural land can play a role in solving the problem of greenhouse gas buildup at very little cost to the economy. These same practices can also result in several long-term benefits related to the improvement in soil quality.  

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