Submitted to: Cotton Research and Extension Report
Publication Type: Experiment Station
Publication Acceptance Date: 2/15/2009
Publication Date: 3/15/2009
Citation: Mitchell, C.C., Delaney, D.P., Balkcom, K.S. 2009. The Old Rotation (CIRCA 1896) - 2008. 2008 Cotton Research and Extension Report. No. 33. p. 22-23. Interpretive Summary:
Technical Abstract: The Old Rotation (circa 1896) is the oldest, continuous cotton experiment in the world. Its 13 plots on 1 acre of land on the campus of Auburn University continue to document the longterm effects of crop rotations with and without winter legumes (crimson clover) as a source of nitrogen for cotton, corn, soybean, and wheat. The 112th year of the Old Rotation experiment continues the trend that began in 1996 when the experiment changed from conventional tillage to conservation tillage and GMO crops. Good yields of most crops were produced in 2008 with irrigation. Non-irrigated cotton and corn suffered through another drought year in Central Alabama. Erratic yields from the winter legume cover crop (A.U. Robin crimson clover) have puzzled project leaders for the last three or four years. We speculate that residue from the cotton defoliant, Dropp® (thidiazuron) and Ginstar® (thidiazuron + diuron), may be affecting germination and survival of the crimson clover planted after cotton harvest. An alternative defoliant was used in the fall of 2008. This is the sixth year that irrigation on the Old Rotation could be compared with non-irrigated plots. Irrigation had a highly significant effect on cotton yields in four of the six years. The last two years, 2007 and 2008, have been drought years and dramatic differences are apparent. Corn grain yields are more erratic from year to year even with irrigation. However, mean corn grain yields over the past six years indicate a highly significant increase due to irrigation. Likewise, mean soybean yields following wheat are increased with irrigation.