October 28, 2015

Long-term field experiments offer new breakthroughs

Researchers from the College of Agriculture are using the oldest continuous cotton experiment in the world to find answers to some of the most vexing problems of modern-day agriculture.

The “Old Rotation,” established in 1896, is the third oldest field crop experiment on the same site in the United States. This rotation also includes rotations with corn, soybean, and small grains and includes winter cover crops, mainly winter legumes. It was placed on the National Register of Historical Places in 1988.

The “Old Rotation” was one of the first experiments to demonstrate and document the value of rotating cotton with other crops and with including nitrogen-restoring legumes in the system. Information from this test provided evidence that rotation with legumes could sustain and actually improve yields of cotton and corn in Alabama soils. Data from this experiment have been the source of numerous scientific, popular, and educational publications on cotton production, cover crops, soil fertility and sustainable agriculture.

Because only minor changes have been made in the cropping systems, this experiment continues to document the effect of these systems on productivity, soil and environmental quality, and sustainable agriculture. The “Old Rotation” consists of six cropping systems in 13 plots on one acre of a Pacolet fine sandy loam on the campus of Auburn University. The experiment sits at the junction of the Southern Piedmont and the Gulf Coastal Plain soil physiographic regions.

Alabama’s long-term field crop and soil fertility experiments on a diversity of soils are a resource that exists nowhere else in the world. These experiments are the basis of soil test calibration and recommendations not only in Alabama but throughout the Southern region of the U.S. Experiments such as the “Old Rotation” (circa 1896) and the “Cullars Rotation” (circa 1911) continue to offer new information on sustainable production as the old plots are adjusted to modern technologies such as conservation tillage and irrigation management in a humid region.

They continue to teach about soil quality influences on long-term productivity. These plots have become a resource for scientific investigations by international scientists from other countries and a resource for study by sciences other than agronomy.

They have contributed to the fact that almost 80 percent of Alabama Coastal Plain farmers use some type of in-row subsoiling and conservation tillage to maximize water use efficiency. The Cullars Rotation is the only site in the U.S. where deficiencies of nitrogen, phosphorus, potassium, sulfur and low pH effects can be observed on five crops during the course of a year. These are extremely valuable teaching tools for a college campus.

Data from the Cullars Rotation has clearly shown that sulfur and micronutrient fertilization on sandy, Coastal Plain soils contribute minimally to increased and sustainable yields of cotton, corn, soybeans and wheat. Five long-term fertility experiments on outlying units date back to 1928 when the experiment fields began. Six began in 1954 in support of the new Soil Testing Laboratory. Today, most of these are being used for alternative crops such as biofuels and forages as well as maintaining validation for soil test interpretation and recommendations

These experiments have shown growers 1) the value of cover crops and high residue management on yields; 2) the value of building soil organic matter; 3) long-term crop yields can be increased using new technologies; and the 4) relative significance of selected primary and secondary nutrients on sustainable production. These projects document soil test calibration for service laboratories throughout the South. They also serve as a conservatory of soil resources for new, relevant research on soils with a prescribed history of amendments.

With non-irrigated agriculture in the humid South, yields are always subjected to rainfall distribution in any season. This can be a severe handicap with short-term field research (three to four years). Including irrigation on the Old Rotation (circa 1896) in 2003 has provided a valuable insight into dealing with supplemental irrigation for field crops.

Switching to high-residue, conservation tillage and GMO crops in 1997 has resulted in dramatic increases in crop yield and almost eliminated pesticide use. Some of these long-term experiments have enabled other researchers to do soil test calibration research on new crops – bioenergy crops that would have required many more years without long-term, established experiments. This project is being included in a new project, “Soil Testing as a tool for Efficient Nutrient Management and Sustainable Production.”

Charles C. Mitchell
Extension Specialist Professor
259 Funchess Hall
Auburn Univ, AL 36849


Auburn University College of Agriculture
Alabama Agricultural Experiment Station
AUBURN, AL 36849
334-844-2783 (PHONE)