Effect of Corn, Soybean, and Cotton Rotation On Yield and Profitability.

Long-term cropping systems research involving cotton, corn, and soybean was initiated in 2004 at the Delta Research and Extension Center to examine the long-term effects of crop rotations on crop yield and profitability.  The systems utilize the most up-to-date technology available including bio-technology in cultivars, high fertility management, and irrigation.  Six rotation systems are included with each component of each system included in every growing season.  The six systems include 1) continuous cotton, 2) cotton/corn [2-yr system], 3) corn/cotton/cotton [3-yr system], 4) corn/soybean [2-yr system], 5) soybean/corn/cotton [3-yr system], and 6) soybean/corn/cotton/cotton [4-yr system].   It will take a total of 12 years for all systems to be at the same point as the initial year of the study.  At after six years the 2-yr systems have completed three cycles and the 3-yr systems have completed two cycles.  Of the system being evaluated, cotton is the only continuous crop and thus has not benefitted from crop rotation.    Corn and soybean yields have been good throughout the study especially since shifting to twin-row production and ESPS (early soybean production system) philosophy.  Glyphosate-resistant cultivars are being used for all crops along with insect resistance.   To date corn yield increase has been measured following soybean production and cotton lint yield increases are 10-12% following corn in the system.  The second year of cotton following corn has not shown the same increase as observed for first year cotton behind corn.  As grain prices increased during the last three years and cotton prices remained the same or declined, having grain crops in the rotation system has increased overall farm income.  Fertilizer costs have risen in the past three adding to the cost of corn production.  Weather-related factors in 2009 have also contributed to lower than normal cotton yields compared to corn and soybean yields.