Extension Ag Update
December 2008
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Research

Long-term impacts of compaction
Candace Pollock, pollock.58@cfaes.osu.edu, (614) 292-3799, and Rattan Lal, OARDC, lal.1@osu.edu, (614) 292-9069

Farmers know that agricultural equipment can cause compaction in no-till crop fields, but Ohio State University researchers have found that, depending on soil type, compaction can be severe and persist for years.  Based on 20 years of compaction studies at various locations in Ohio, just one year of harvest traffic on clay soils can reduce corn yields by as much as 40 percent, and the impacts from compaction can persist for as long as eight years. The research, "Axle-Load Impacts on Hydraulic Properties and Corn Yield in No-Till Clay and Silt Loam," has been published in the November/December issue of Agronomy Journal.

"This is one of the few long-term compaction studies in the nation. We know that equipment causes compaction, but we wanted to know how long that compaction lasts and how severe it really is," said Rattan Lal, an Ohio State University soil scientist with the Ohio Agricultural Research and Development Center. "What we've learned is that it's better to take steps to prevent compaction rather than run into the difficulties associated with compaction and struggle to try to eliminate it."

Lal and his colleagues made a one-time distribution with a single axle 20-ton grain cart and a single axle 10-ton grain cart across fields with two types of soils: clay and silt loam, and then measured how long it took for the fields to recover from the effects of compaction. While compaction from clay soils persisted for years, silt loam soils escaped serious compaction problems.  "Unlike silt loam soils, clay soils drain poorly and don't respond to the freezing and thawing process during winter, so compaction tends to persist more and its impact on crop growth and yield is much more severe," said Lal.

  • Lal said farmers can reduce the compaction hazard through a variety of methods:
  • Practicing minimal tillage techniques, such as chisel plowing or subsoiling.
  • Relying on soil critters, such as earthworms, to break up the soil through natural processes. The study found that compaction can have an impact on earthworm populations, decreasing numbers 70 percent in clay soils and 50 percent in silt loam soils.
  • Growing a cover crop, such as alfalfa, that has a taproot system and can extend deep into the soil. Research Lal conducted in Africa using pigeon peas, a type of taproot plant, showed compaction was eliminated within two years.
  • Leaving crop residue in the field. The residue acts as a buffer to dissipate any wheeled traffic.
  • Using dual-axle instead of single-axle equipment and wider tires to distribute weight.
  • Practicing controlled traffic -- a method whereby all farm equipment is the same width so that traffic is confined to specific paths year after year, and the remainder of the soil is untouched.
  • Planting or harvesting crops only under ideal environmental conditions. Lal's compaction research also found that working in fields during rainy conditions increased the severity of compaction.

Lal plans to continue the long-term compaction study, compacting the soil every year and then implementing various control techniques to determine which one would work best. Compaction can have a number of impacts on the soil and the plants growing in it. Compaction destroys the soil structure and causes erosion by keeping water out. It prevents plant roots from penetrating deep into the soil, and traps carbon dioxide while preventing oxygen from reaching plant roots. The result suffocates the plant either killing the plant or impacting yield performance.


Global Climate Impact on Illinois
Diana Yates, Life Sciences Editor | 217-333-5802; diya@illinois.edu

Extreme weather, drought, heavy rainfall and increasing temperatures are a fact of life in many parts of the U.S. as a result of human-induced climate change, researchers report today in a new assessment. These and other changes will continue and likely increase in intensity into the future, the scientists found.

Researchers representing 13 U.S. government science agencies, major universities and research institutes produced the study, “Global Climate Change Impacts in the United States.” Commissioned in 2007, it is the most comprehensive report to date on national climate change, offering the latest information on rising temperatures, heavy downpours, extreme weather, sea level changes and other results of climate change in the U.S.

The 190-page report is a product of the interagency U.S. Global Change Research Program, led by the National Oceanic and Atmospheric Administration. It is written in accessible language, intended to better inform members of the public and policymakers about the social, environmental and economic costs of climate change. It focuses on effects by region and details how the nation’s transportation, agriculture, health, water and energy sectors will be affected in the future.

Don Wuebbles, the Harry E. Preble Professor of Atmospheric Sciences at the University of Illinois and a contributor to the assessment, outlined the current and predicted effects of climate change in the U.S. Midwest.  “We well recognize that Earth’s climate varies naturally and has been warmer and cooler in the past,” Wuebbles said. “But we also know that the climate changes we are experiencing today are largely the result of human activities.”

Average temperatures have risen in the Midwest in recent decades, Wuebbles said, especially in winter. The growing season has been extended by one week. Heavy downpours are now twice as frequent as they were a century ago, he said, and the Midwest has experienced two record-breaking floods in the past 15 years.

These trends are expected to continue into the future, Wuebbles said. Average annual temperatures are expected to increase by about 2 degrees Fahrenheit over the next few decades, and by as much as 7 to 10 degrees by the end of the century, he said, with more warming projected for summer than winter.

Precipitation is expected to increase in the winter and spring, while summer precipitation will likely decline.   “More of the precipitation is likely to occur during heavier events,” Wuebbles said.   As temperatures and humidity increases, heat waves, reduced air quality and insect-borne diseases are more likely to occur. Pollen production and the growth of fungi will also be stimulated, he said. Heavy downpours can overload drainage systems and water treatment facilities, increasing the risk of waterborne diseases, he said.

The Great Lakes, which contain 20 percent of the planet’s fresh surface water, will also be affected by the changing climate, Wuebbles said. Depending on the extent of climate change, average water levels in the Great Lakes could drop by as much as 2 feet in this century, he said. This would affect beaches, coastal ecosystems, fish populations, dredging requirements and shipping.

Some of the effects of the changing climate are inevitable and will require human and animal populations to adapt, Wuebbles said.  Other effects can be mitigated by limiting future emissions of carbon dioxide and other greenhouse gases that contribute to climate change, he said.   University of Illinois atmospheric sciences emeritus professor John Walsh and University of Illinois research associate Katharine Hayhoe, who is also a geosciences professor at Texas Tech University, were among the scientists who contributed to the report.

The full report, “Global Climate Change Impacts in the United States” is available http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts