Feasibility of Four Year Crop Rotations in Western Kansas.

Research on 4-year crop rotations with wheat and grain sorghum was initiated at the Kansas State University (KSU) Southwest Research-Extension Center (SWREC) near Tribune in 1996. Rotations were wheat-wheat-sorghum-fallow (WWSF) and wheat-sorghum-sorghum-fallow (WSSF) along with continuous wheat (WW). Soil water at wheat planting averaged about 230 mm following sorghum, which was about 75 mm more than the second wheat crop in a WWSF rotation. Soil water at sorghum planting was approximately 30 mm less for the second sorghum crop compared with sorghum following wheat. Grain yield of recrop wheat averaged about 80% of wheat following sorghum; grain yield of continuous wheat averaged about 70% of the yield of wheat following sorghum.  Wheat yields were similar following one or two sorghum crops. Similarly, average sorghum yields were the same following one or two wheat crops. Yield of the second sorghum crop in a WSSF rotation averaged about 70% of the yield of the first sorghum crop.