Alabama's Old Rotation experiment (circa 1896)  on the campus of Auburn University is the oldest, continuous cotton experiment in the world.  For over 100 years, this experiment demonstrated the benefits of crop rotation and winter legume cover crops in cotton production systems in the Deep South.  In 1997 a major management change occurred when the entire experiment shifted from conventional tillage to high residue, conservation tillage.  Another major change occurred in 2003 when irrigation was installed on half of each plot.  The effects of these changes on yields of cotton, corn, soybean and wheat will be discussed with special emphasis on the last 5 years of irrigated versus non-irrigated plots.