ABSTRACT

After 106 cropping years, Alabama's Old Rotation experiment (circa 1896) continues to document the long-term effects of crop rotation and winter legumes on sustainable cotton production in the Deep South. For 100 years the experiment was under conventional tillage. However, since 1997, all crops planted on the Old Rotation have benefited from minimum tillage. Coincidentally, record yields of all crops grown on the Old Rotation have been achieved since conservation tillage techniques have been implemented. Long-term yields suggest that winter legumes are just as effective as fertilizer N in producing optimum cotton yields. Yields are also highly correlated with soil organic matter that reflect the long-term treatments. In the past, crop rotation benefits have had a small effect on cotton yields, considering yield levels and crop value. These benefits are apparently enhanced under conservation tillage. Soil quality differences, e.g., aggregation and soil tilth, due to rotations and cover cropping are dramatic and are likely to increase under conservation tillage.