An ecological approach to strengthen weed management in the semiarid Great Plains

Cropping systems in the semiarid Great Plains are rapidly changing. Previously, winter wheat-fallow was the prevalent system; now, because of no-till practices, producers are diversifying their rotations to include alternative crops. Yet, weed management is often ineffective because of herbicide-resistant weeds and low profit margins. A possible solution is ecologically based weed management, where cropping systems are designed to lower weed community densities and improve crop competitiveness to weeds. Both winter and summer annual crops are grown in the Great Plains, which can help manage weeds because growth periods differ considerably between crop types. Designing rotations to include two winter/spring crops followed by two summer annual crops can reduce weed community density 12-fold compared to less diverse rotations. This rotation design favors natural weed seed decline in soil yet avoids proliferation of weed densities in crops with similar life cycles. However, tillage minimizes the effect of rotation design on weed community. A second component of the ecological approach is to strengthen crop competitiveness with cultural practices. Combining three practices together improved crop competitiveness three- to five-fold. With some crops, such as proso millet, cultural systems are so effective that herbicides may not be needed for in-crop weed control. Designing rotations based on a cycle-of-four with winter and summer annual crops also accrues ancillary benefits such as increased yields and economic returns as well as improved resource-use-efficiency. Furthermore, the ecologically based approach will enable producers to ameliorate the negative impacts of herbicide-resistant weeds and rising input costs. © 2003 Elsevier Science B.V. All rights reserved.