Technical Abstract: Water supply is a major constraint for crop production in dryland agriculture across the world, and extensive research has been conducted to improve water use. In the grass steppe of the United States, water use has improved through a series of management advancements, such as preservation of crop residue on the soil surface, no-till, and crop diversity. We have observed an additional advancement after several years of no-till rotations; some crops synergistically improve water-use-efficiency (WUE) of following crops. For example, proso millet (Panicum miliaceum L.) produces 24% more grain with the same water use following corn (Zea mays L.) than following winter wheat (Triticum aestivum L.). The presence of corn and dry pea (Pisum sativum L.) in the rotation also improves WUE of winter wheat. Furthermore, synergism among crops increases tolerance of weed interference. The cause of synergism is not known, but identifying synergistic crop sequences and designing rotations to include these sequences can improve water conversion into grain for dryland agriculture. Because of no-till, crop diversity, and synergism, producers in the U.S. steppe have doubled land productivity with the same water supply.