Dairy Channel: Dairy Channel: Get the dirt on the latest carbon sequestration research in soils


Two research projects currently under way in Ohio will involve producers in Columbiana and Mahoning counties.

I have pledged some of my time to help with important research projects involving E. coli 157 bacteria in dairy cows and carbon sequestration in soils. I will be contacting producers to set up farm visits for the collection of data and samples in conjunction with these projects.

Carbon sequestration. The 2002 farm bill calls for research into the levels of carbon in soils. Research is currently under way to evaluate soil carbon levels as affected by cropping system, tillage, livestock manure use and other aspects of soil management.

The following is a brief explanation of the global carbon cycle and its role in possible global warming:

Plants convert carbon (CO2 from air) into plant sugar, which is the source of all plant and soil carbon on Earth. Of the total carbon converted from CO2 into plant sugar, 50 percent is converted back to CO2 by plant respiration.

Vegetation. The other 50 percent is converted into vegetation. Vegetation in the form of grasses, weeds, crops and forests on earth contain about 560 billion metric tons of carbon.

Soils and plant litter contain about 1.5 trillion metric tons (almost three times as much).

In recent years, researchers calculate that the Earth loses a net of 5 billion metric tons of carbon to the atmosphere per year, which explains why the CO2 content of the atmosphere is increasing.

Offset. By sequestering carbon, agriculture helps to offset greenhouse gas emissions. Rangeland and deep-rooted perennial crops help keep carbon dioxide, the principal greenhouse gas, from the atmosphere.

Agriculture also emits greenhouse gases, mostly methane from cattle, but also nitrogen oxide from fertilizer and emissions from fossil fuel use. Windbreaks to reduce erosion also can help sequester carbon – and when they shelter buildings, reduce energy consumption and the greenhouse gases produced by burning fossil fuels.

Minimum till, no till and other conservation practices in agriculture reduce greenhouse gas emissions by lowering use of machinery and the emissions from fuel burned.

By enhancing organic materials in soil, these practices increase soil’s ability to sequester carbon.

Questions. What is the greenhouse effect, and what do we mean by climate change?

Certain gases such as carbon dioxide, methane, and nitrous oxide act in the atmosphere much as the glass in a greenhouse, trapping heat from sunlight near the Earth’s surface. In the proper balance and occurring naturally, these atmospheric gases are essential to life on Earth.

Climate changes. Climate change – long-term fluctuations in temperature, precipitation, wind, and all other aspects of the Earth’s climate – has been a natural phenomenon over the millennia, induced by such events as volcanic eruptions, ice ages, and changes in forest cover and ocean currents and temperature.

Estimates are that without naturally occurring greenhouse gases, the Earth’s temperature would be 60 degrees (Fahrenheit) cooler than it is today; during the last ice age the temperature was 9 degrees cooler than current temperatures.

With the advent of the industrial revolution, large quantities of carbon dioxide and other greenhouse gases began to be introduced into the Earth’s atmosphere.

The result may well be climate change, this time because of human activity.

Ag potential. What could happen to agriculture?

If climate changes and temperatures rise, there are a number of potential effects. The timing and length of growing seasons might shift geographically, which would alter planting and harvesting dates and likely result in a need to change crop varieties currently used in a particular area.

Seasonal precipitation patterns and amounts could change. With warmer temperatures, evapotranspiration rates would rise, which would call for much greater efficiency of water use.

Weed and insect pest ranges could shift.

Perhaps most important of all, there is general agreement that in addition to changing climate, there would likely be increased variability in weather, which might mean more frequent extreme events such as heat waves, droughts and floods.

What in the world are we doing about it? The likelihood and potential impacts of climate change have been the subject of intense concern and debate over the past decade.

Framework. One result of this discussion was the signing of the Framework Convention on Climate Change (FCCC) at the Earth Summit in Rio de Janeiro, Brazil, in June 1992. The United States is a signatory to that convention, which the U.S. Senate ratified in 1993.

In signing the Framework Convention on Climate Change, the developed nations pledged to “take the lead in combating climate change and the adverse effects thereof.”

To this end, the United States and other countries pledged to seek to reduce their emissions of greenhouse gases to their 1990 levels by the year 2000.

Contribution. What is the American contribution?

The United States generates about 20 percent of the total global greenhouse gases emitted annually. Of this U.S. share, American agriculture generates a relatively small portion: 1.8 percent of the carbon dioxide, 14 percent of the methane and 7.5 percent of the nitrous oxide.

Agricultural emissions of carbon dioxide come from fertilizer and pesticide manufacture, field machinery use, transportation, irrigation, livestock production and crop drying.

Globally, methane emissions come from rice paddies (28 percent), ruminant animals (20 percent), wetlands (11 percent) and other sources (6 percent).

Most methane emissions from agriculture in the United States come from livestock.

Nitrogen oxide in agriculture is emitted primarily by nitrogen fertilizers, which, once applied, break down in the soil and can become airborne in their gaseous forms.

Any help? How can agriculture help?

A number of measures exist that agriculture can take both to increase the quantity of carbon it sequesters (captures) and to reduce its share of greenhouse gas emissions: Use low-greenhouse gas fuels, such as diesel and alcohol-based fuels from biomass (woody and herbaceous plant tissue and animal wastes that can be converted to energy); better manage cattle waste and, if possible, trap or process methane, or both, for its energy and nutrient content; and apply nitrogen fertilizers only when and in quantities and forms needed by crops.

This reduces emissions of the oxide.

Increase conservation tillage and other crop residue management practices to lower emissions from equipment and increase soil organic-matter content.

By carefully husbanding resources and land uses that accumulate carbon (sinks) – such as lands primarily in perennial crops and forest – and by changing the practices to avoid generating green house gases, agriculture can make an important contribution to meeting the goals of the Framework Convention on Climate Change.

Knowledge. Do we know enough? We lack specific knowledge about the nature and effects of current climate change trends (and there are still many uncertainties and disagreements).

We also need to know more about the actual capacity of agriculture to sequester carbon.

Initiatives are being taken by USDA and others to assess, with greater precision than has been done up to now, the nature and extent of carbon sequestration in soil, in the diverse crop systems, and in the many microclimates found in the United States.

Benefits. What are the benefits of taking action now?

The beauty of doing something now about climate change is that almost any action taken helps to solve other problems.

Retaining ground cover for the purpose of storing carbon also can reduce or prevent erosion; restore damaged land and water resources; reduce local air pollution; reduce water pollution by reducing runoff; enhance wildlife habitat and biodiversity; and increase production of biomass and other alternative crops.

Changing tillage practices, preserving crop residues and similar measures can reduce the need for fertilizer inputs that are energy-intensive in their manufacture and application (both of which can produce local pollution and require the use of fossil energy, much of it imported) and also save money.

It can also decrease emissions of oxides of nitrogen by applying nitrogen fertilizers only when and in quantities needed and decrease the costs of chemical and mechanical treatments of crops and the labor they require.

In addition, it can reduce field activity with equipment, thereby reducing farm emissions from fossil fuels; and recognize animal wastes as a resource, rather than a burden, by using them for energy to supplant other forms of energy, and by better using them for fertilizer to substitute for commercial nutrient sources.

Obligations. Likewise, doing something about other environmental problems associated with agriculture – erosion, air pollution, water pollution, animal waste, energy efficiency and alternative energy sources – can help meet the nation’s obligations regarding greenhouse gases and climate change.

The USDA, through the Natural Resources Conservation Service (formerly Soil Conservation Service), is preparing an environmental scan of the status, conditions, and trends of natural resources on America’s nonfederal land, as required by the Soil and Water Resources Conservation Act of 1977 (RCA) Public Law 95-192.

The appraisal will help guide the updating of the National Conservation Program, which directs USDA’s natural resource conservation policies and programs.

Ten other USDA agencies and 10 non-USDA agencies are full partners in this effort.

More info. For more information, contact James Maetzold, USDA, Natural Resources Conservation Service, Natural Resources Inventory Division, P.O. Box 2890, Washington, DC 20013; phone, 202-720- 0132; fax, 202-690-3266.

(The author is an agricultural extension agent in Columbiana County. Questions or comments can be sent in care of Farm and Dairy, P.O. Box 38, Salem, OH 44460.)


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