Changes in Soil Nutrient Levels over Time from Multiple Cropping Systems in the Centennial Rotation.

Mississippi’s Centennial Rotation was established in 2004 to commemorate the 100-year anniversary of the Delta Research and Extension Center.  Agriculture was rapidly changing and technological advances were evident in all aspects of production.  Since the onset of the 100-year rotation, cotton has lost dominance on the landscape and grain crops, corn and soybean, have appeared along with the infrastructure to handle the crops.  Rotations were set up with all crops grown during each growing season and include five rotation system along with continuous cotton.  The rotations include: 1) continuous cotton, 2) cotton/corn [1:1], 3) cotton/ cotton/corn [2:1], 4) corn/soybean [1:1], 5) soybean/corn/cotton [1:1:1], and 6) soybean/corn/cotton/ cotton [1:1:2].  The rotations are replicated four times allowing for statistical comparison after only a few years.  With 2-yr, 3-yr, and 4-yr rotations, it takes 12 years for all cycles to repeat with some completing six, four, or three cycles.  The annual crops are managed with the latest technology and cultural practices with yields determined along with an estimate of both nutrient uptake and nutrient removal.  Following harvest and prior to any primary tillage, soil samples are taken to monitor changes in pH, soil nutrients, and other soil test parameters.  As expected, grain crops take up and remove greater levels of nutrients and should more rapidly affect soil nutrient levels.  With record yields for corn and soybean for the last few years, producers have removed record levels of soil nutrients and should be relying heavily on soil testing in order to maintain soil productivity.  Sulfur deficiency has been to surface in some areas and will continue to get worse unless supplemental fertilizer S is supplied.  The Centennial Rotation is providing useful information with respect to the utilization of the latest technology and the advantages to crop rotation.