Summer Fallow for Dryland Winter Wheat in the Semiarid Great Plains 1

A study comparing fallow‐wheat ( Triticum aestivum ) with continuous wheat under semiarid conditions showed fallow‐wheat average yields to be over three times greater than average continuous wheat yields. The fallow‐wheat system provides stable production with no crop failures when compared with continuous wheat, which failed more than 30% of the time. Average water‐use efficiency for fallow‐wheat was 80% greater than that for continuous wheat when annual precipitation was between 24.6 and 43 cm. This showed that fallow‐wheat was the most efficient means of producing winter wheat when average annual precipitation was less than 43 cm. Fifty‐eight or more centimeters of annual precipitation was required before continuous wheat with N fertilizer used water as efficiently as fallow‐wheat without N. Nitrogen content of fallow‐wheat was 0.22% higher than that from continuous wheat. Nitrogen fertilizer was necessary for maximum continuous wheat yields, water‐use efficiency and N content. But in this semiarid area, average fallow‐wheat yields without N were 2.6 times better than continuous wheat yields with N. Continuous wheat with fertilizer N used water only 71% as efficiently as fallow wheat without N fertilization. Furthermore, N content of fallow‐wheat grain without N fertilization was as high as that of continuous wheat with fertilizer N. In all aspects, the fallow winter wheat cropping system was much superior to continuous winter wheat and proved necessary for stable winter wheat production under semiarid conditions in the Great Plains.