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The Centennial Rotation
Dr. M. Wayne Ebelhar, Research Professor and Agronomist, Mississippi State University at the Delta Research and Extension Center
recently spoke about managing cotton and corn with crop rotation and cover crops at the National Conservation Systems Cotton & Rice Conference.
Photo by John LaRose, Jr.
After 12 Years, This 100-Year Trial Shows Rotation Pays
BETTY VALLE GEGG-NAEGER
MidAmerica Farmer Grower
MEMPHIS, TENN.
In a presentation on Managing Cotton And Corn With Crop Rotation And Cover Crops at the National Conservation Systems Cotton & Rice Conference recently, Dr. M. Wayne Ebelhar, Research Professor and Agronomist, Mississippi State University at the Delta Research and Extension Center, highlighted The Centennial Rotation underway at the University.
“That’s my claim to fame,” he said, noting he began the 100-year study in 2004 in observance of the 100th anniversary year of the Stoneville campus which was instituted in 1904.
In his presentation, Ebelhar referred to the Morrow plots, the longest running trials in the United States on campus at the University of Illinois in Champaign-Urbana, where he worked previously. The university library is built underground there to prevent shading on the plots. Trials such as this and one in England were the inspiration for The Centennial Rotation which he established at Stoneville. Rotations date back to the 1700s, but fell by the wayside when more money could be made with continuous crops such as cotton.
While crop rotation was in use over 300 years and has been practiced for many, many years, it has regained popularity in the last few decades especially in the Mid-South USA. Often, government programs for farmers favored continuous cotton for optimum profitability with dryland production practices and favorable prices or price supports. As irrigation appeared across the Mid-South and Southeast, many grain crops, corn and soybean, had improved yields and offered profitability in whole-farm enterprises.
In the Mid-2000s, grain crop acreage increased and cotton acreage declined. Research in the Mississippi Delta, initiated by Dr. Ebelhar in 2000 at multiple locations, has shown an average 9 percent to 17 percent yield increases for cotton following corn, compared to cotton following cotton. These were the average results across at least 10 years and range from a yield decline to more than a 50 percent yield increase in some years.
“In 2004 I set up this Centennial Rotation at the experiment station involving a combination of cotton, corn and soybean in rotation. The rotation experiment’s oldest continuous plot is a cotton based rotation with cotton as the only continuous crop because at that time cotton was still king. I was interested in the new century at Stoneville and this was something new and different which could take advantage of many new technologies.”
This trial shows the advantages of crop rotation with cotton and how yields can be increased over a long period without increasing cotton inputs. The study plots deal with rotations of corn, cotton and soybeans in two-year, three-year and four-year rotations. The two-year platt includes corn and cotton; the three-year system uses corn, cotton and soybean; and the four-year rotation is one of soybean, corn, cotton, cotton.
“The uniqueness of my study is that it’s a replicated study. Treatments in the study appear more than one time and every treatment is the same. I have all the possible combinations of soybeans, corn, cotton and cotton,” said Ebelhar.
The two-year plot includes one plot of corn and one of cotton. The next year the plots are rotated to the other crop.
“What that does is it allows us to look at the impact of the weather and prices that year,” he said. “The rotations can often be influenced by the year. This range in responses has been shown in other studies as well.”
The same treatments allows the study to discern how the weather and any other variable affects the treatment.
“At the end of the 12 years, we are back where we were in year one, and we start another 12-year study,” he said. The two-year cycle has repeated six times in that 12 years, the three-year cycle has repeated four times and the four-year cycle has repeated three times.”
Biotech seeds are used in the plots. There’s Liberty Link corn, Liberty Link Cotton and Liberty Link soybeans currently in the study because of herbicide resistant weeds. Soybeans are on a twin-row planting system (two rows on the same bed), with single rows for corn and cotton. Furrow irrigation is used in the study.
“Also, every year we take soil samples, looking for changes in fertility (soil nutrients and other soil characteristics) and impact on yield,” he noted. One important observation is that a large volume of nutrients are being removed with the grain crops.
“We are removing a lot of nutrients. I’m keeping track of nutrient uptake and removal with time and nutrient loss. We total all the NPK and S with time to see how much we are pulling down. These are long-time studies, looking at what happens over a long period. Soil tends to have huge reserves of nutrients but with time these reserves can be depleted.
“At present, we are averaging about 20 percent to 22 percent higher yields of cotton following corn compared to continuous cotton. The rotation effect is the only difference. We have never had a negative yield in this particular study. In some of our best years when continuous cotton yielded 1400 lb lint/acre, cotton following corn produced 1900 lb/acre (500 lb/acre increase).
“It’s really a successful study, and it’s providing a lot of information.”
The Centennial project is scheduled to run through 2104, the 200th year for the university.
“I don’t plan to be there to harvest the last crop,” he quipped. However, the fruits of his labor will speak for him.
The advantages of crop rotation outweigh the disadvantages, but environmental extremes can change even the best intentions in crop rotations. One of the strong points in support of the current research underway at Stoneville is replications and the fact that every crop in a rotation sequence is grown each year. Thus, shifts in market prices, that can vary depending upon the year, can be evaluated in the economic analysis.
Farmers can access information about the study by searching for Plant Management Network. Follow the link to webcasts and scan the list for “The Value of Rotations - Lessons Learned Corn-Cotton Rotations and the Mississippi Centennial Rotation - M. Wayne Ebelhar, Mississippi State University, January 2018.” ∆
BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower
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