ARS Improves Yields in 100-Year-Old Experiment
The 106th cotton crop
grown at Auburn University
in the "Old Rotation"
experiment, the world's oldest
continuous cotton experiment.
1896. McKinley beats Bryan to become president. The first
modern Olympic games take place in Athens. George Burns is born. And
Auburn University professor J.F. Duggar starts a cotton experiment near
the Alabama campus to try to prove that sustainable cotton production
could be achieved in the state if farmers used crop rotations that included
legume cover crops in winter.
That experimentknown as the Old Rotationis still going on today, but Auburn researchers, led by professor Charles Mitchell, the current curator of the experiment, decided to update it after its 100th anniversary celebration. The researchers were getting valuable information and good yields of cotton, but they thought they could get more out of the world's oldest continuous cotton plots and the third oldest of any crop experiment in the United States.
They asked for help from the Conservation Systems Research Team at the Soil Dynamics Laboratory, an Agricultural Research Service laboratory located on campus. With the changes ARS researchers made, record yields have since been noted.
Led by agronomist Wayne Reeves, the ARS team decided to
use a form of conservation tillage with specialized deep tillage. This
method alleviates soil compaction while maintaining crop residue cover
on the soil. They coupled this with new herbicide-resistant varieties
of cotton, corn, and soybean. With the new system, there was an average
increase in cotton yield of 22 percent.
"We noticed dramatic results almost immediately;
soil carbon and associated soil quality and productivity have increased
more rapidly than we thought possible,"Reeves says. A record 1,600
pounds of cotton lint per acre (more than 3.3 bales) was measured on
one plot in 2001. The previous record (before no-till was introduced
to the fields) was 1,490 pounds of cotton lint per acre.
Also, yields of corn increased 38 percent and wheat yields
increased 81 percent when these crops were grown in rotation with cotton.
A record corn yield of 236 bushels per acre was harvested from one plot
in 1999, and record wheat yields were consecutively set in 1999, 2000,
Conservation tillage farming provides many economic and
environmental benefits to the farmer. Since the soil is not touched
after harvest until the next growing season, there is less erosion because
of the residue left on the fields. Reeves stresses the need for crop
residues in conservation tillage, especially in warmer regions. This
residue traps moisture and nutrients in the soil and suppresses weeds,
often reducing the amount of chemicals the farmer must use.
Conservation tillage also requires less machinery and
less labor than conventional tillage. Reeves says, "A farmer may
have to modify or purchase some new equipment with conservation tillage,
but that will pay off with increased yields and less money spent on
herbicides, fuel, and labor."
The plots in the experiment that use crop rotation have
always raised the cotton yield some, but the rotations really improve
yield when conservation tillage is used. Crop residues from the rotation
crops and winter legume cover crops increase soil carbon or organic
matter and improve water and nutrient use by the cotton and rotation
The ARS and Auburn scientists have just started to add
irrigation to half of the experiment. Reeves and Mitchell are curious
to see how that will affect yields and soil quality when used with conservation
farming. More information about the Old Rotation, including photos and
charts, can be found at www.ag.auburn.edu/dept/ay/cotton.htm.By
David Elstein, Agricultural
Research Service Information Staff.
This research is part of Integrated Agricultural Systems,
an ARS National Program (#207) described on the World Wide Web at www.nps.ars.usda.gov.
D. Wayne Reeves
is now with the USDA-ARS J.
Phil Campbell Sr. Natural Resource Conservation Center, 1420 Experiment
Station Road, Watkinsville, GA 30677; phone (706) 769-5631, fax (706)
"ARS Improves Yields in 100-Year-Old Experiment" was published in the May 2003 issue of Agricultural Research magazine.