Tuesday, November 6, 2007
151-7

Impact of Crop Rotation on Winter Wheat Yield in a Semiarid Environment.

Thandiwe Nleya, John Rickertsen, and Bruce Swan. South Dakota State University, South Dakota State Univ., 1905 Plaza Blvd., Rapid City, SD 57702

The traditional crop rotation in the semi-arid region of western South Dakota was winter wheat-fallow. The fallow phase was used to store soil water for the subsequent winter wheat crop. Widespread adopting of reduced-tillage systems in the region has increased water storage efficiency and this has allowed for the transition from the traditional rotation to intensified and diversified no-till cropping systems. A long-term rotation study was established in 1994 to compare the traditional winter wheat-fallow to no-till, diversified rotations. Nine rotations, two to six years in duration, are currently being evaluated. All phases of each rotation are grown each year. Reduced and no-till production practices are used to grow the crops except in the winter wheat–fallow rotation. Over the last 10 years, winter wheat yield in the conventional winter wheat-fallow rotation has averaged 3,292 kg ha-1 while winter wheat in diversified rotations that include broadleaf crops (winter wheat-safflower-millet) or corn (winter wheat-corn-millet) averaged 2,552 kg ha-1. Over the same time period, winter wheat in the winter wheat-millet rotation averaged 2,150 kg ha-1. Yields of alternate crops including sunflower, safflower, chickpea and corn varied widely, and were strongly influenced by growing season precipitation.