Long-Term Effects of Conservation Systems on Productivity for the Old Rotation.

Winter legumes in cotton (Gossypium hirsutum L.) production is not new to the Southeast. In 1896, the Old Rotation experiment at Auburn University was established to study the feasibility of producing cotton in crop rotations with winter legumes managed as a green manure crop. Throughout the experiment, production practices have changed over time to reflect prevailing best management practices. For example, genetically modified cotton has been planted since 1997 and conventional tillage was replaced with conservation tillage in the same year. These changes have the potential to impact the profitability and associated risk. This study evaluates cotton lint yields, profitability, and economic risk in eight cotton cropping systems (continuous cotton, cotton-corn [Zea mays L.], and cotton-corn-soybeans [Glycine max. (L.) Merr.]) with varying fertilizer regimes and winter legumes. Three time periods were used in the analysis: 1) the period prior to conservation tillage (1978-1996); 2) the period after conservation tillage (1997-2016); and 3) the period 1978-2016.