Fall Chiseling for Annual Cropping of Spring Wheat in the Intermountain Dryland Region1

Comparisons were made among annual cropping, annual cropping with fall chiseling, and a spring wheatfallow rotation with chiseling after harvest under a climate with near uniform monthly precipitation of 2.5 cm. Because cropping season precipitation averaged only 9.1 cm, soil water storage before planting was necessary to ensure crop production. “Annually cropped” plots averaged 15.0 cm stored available water per 180‐cm depth at planting, whereas “annually cropped‐fall chiseled,” and “cropped‐fall chiseled‐fallowed” plots averaged 21.3 and 22.9 cm, respectively. Soil water storage from the spring of the summerfallow year until the spring of the crop year was dependent upon the previous over‐winter storage (r2 = 0.65). When this initial storage was less than 23.9 cm per 180‐cm depth, water in storage was increased by summer‐fallowing. However when the initial storage exceeded 23.9 cm, summer‐fallowing resulted in a soil water loss. As crop yields were dependent on soil water storage at planting time (r2 = 0.68), it was possible to estimate in the spring what yields would be with annual cropping, and also what extra water might be stored by fallowing as an alternative practice. Nonfertilized, “annually cropped” and “annually cropped‐fall chiseled” plots contained approximately the same amount of soil NO3‐N at planting, but only the chiseled plots with their extra stored water produced a yield response from fertilizer N. In comparison, non‐fertilized fallowed plots con tamed 1½ times as much NO3‐N, and no yield response was obtained with fertilizer N.