Cotton/Corn Rotation In the MidSouth - Effect On Yield and Nematode Dynamics.

Long-term corn/cotton rotations were begun at two sites in the Mississippi Delta in 2000 with corn followed by two years of cotton on soils that are characteristic of the predominant cotton and corn soils.  At each location, Delta Research and Extension Center (DREC) and Tribbett Satellite Farm (TSF), each corn or cotton section had a factorial arrangement of nitrogen (N) and potassium (K) treatments.  A summary of long-term yields from cotton following corn compared to cotton following cotton resulted in a 10% to 18% increase in lint yield for cotton following corn compared to cotton following cotton.  Nematode infestations continue to grow in the Mississippi Delta and are best addressed through crop rotations that involve non-host crops.  Reniform nematodes (Rotylenchulus reniformis) have been an increasing problem where continuous cotton has been grown.  Shifting to corn every other year or at least one year out of three has been shown to curtail reniform nematode numbers.  The initial long-term studies (2000), was adapted in 2007 to address nematode dynamics.  Soil samples, taken after planting, at mid-season, and post-harvest to monitor nematode numbers, showed no statistical relationship between N or K in either cotton or corn.  Reniform nematode numbers, in most years, started out higher in corn following two years of cotton but declined through the season.  With cotton following corn, the reniform nematode numbers were lower than either of the other two systems (cotton following cotton or corn following two years of cotton).  In the second year of cotton, nematode numbers were much higher in the post-harvest samples compared to the other two systems.  Rootknot nematodes (Meloidogyne incognita) were not found to be a problem at either study site.  Both cotton and corn are hosts to the rootknot nematode and must be addressed through methods other than crop rotation.