The Value of Rotations - Lessons
Learned Corn-Cotton Rotations and the
Mississippi Centennial Rotation
By M. Wayne Ebelhar, Ph.D.
Mississippi State University
Delta Research and Ext. Center
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Crop rotations and green manure crops date back to the 1700's in some areas and were prominent in the US in the early 20th century. As animal agriculture decreased and mechanization increased, the need for livestock feed decreased and highly profitable crops to sell gained prominence and a larger portion on the landscape. In more recent years, the advantages of rotation became more evident as problems in mono-crop agriculture increased. Grain crops became more profitable and could be grown as part of a profitable whole-farm enterprise.
Today’s presentation will focus on research in the Mississippi Delta that illustrates the advantages of crop rotation with cotton and how yields can be increased over a long period without increasing cotton inputs. Although yields of cotton following corn are 9 to 20% higher than continuous cotton, producers can see problems in some years as environmental conditions such as rainfall can impact good cotton growth in a negative way. While research has been conducted in the Mid-South US, the implications are far reaching across the Cotton Belt. This research has concentrated on cotton, corn, and soybean, grain sorghum can also be used in areas where water may be limiting corn production. Today’s presentation will also summarize the first 12 years of the Centennial Rotation with emphasis on crop yield, profitability, and both nutrient uptake and removal. As grain crops are introduced into production systems, greater nitrogen, phosphorus, potassium, and sulfur removal is quite evident. Producers must use sound fertilization practices (soil testing and application of nutrients) to maintain high yields. Nutrient reserves can be removed far more rapidly with grain crops and rotation compared to mono-crop cotton.
Today’s presentation contains data from research on crop rotations in the Mississippi Delta dating back to 2000. The Centennial Rotation (established in 2004) continues to provide valuable information on multi-crop rotation sequences including cotton, corn, and soybean. Long-term research is a valuable tool in understanding the overall impact of crop rotation. As producers deal with more problems associated with growing the same crop in the same field over and over (insect and disease pressure, herbicide resistant weeds, and nematodes); crop rotations allow for shifting many cultural practices and pesticide usage.
Advantages outweigh 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.