Abstract :
Because of improved water management, producers in the Great Plains are diversifying their crop rotations. A benefit of crop diversity is that some crop sequences can increase grain yields. Along with yield benefits, we also have noted that water use efficiency (WUE) of some crops can be improved by preceding crops. For example, WUE of winter wheat (Triticum aestivum L.) and proso millet (Panicum miliaceum L.) is improved if corn (Zea mays L.) is included in the rotation. If crops respond favorably to rotation, they either increase plant capacity and resource use or improve resource use efficiency (synergism). We suggest that the soil environment remaining after some crops, such as corn or legumes, synergistically improves growth efficiency of following crops. However, synergism appears to be specific between crops. We also suggest that synergism among crops would be assessed most accurately in long-term cropping systems studies.
