The accompanying graph shows the soil water content for summer fallow, spring wheat, and safflower at approximately 2-week intervals during the 2003 growing season. For each cropping treatment, measurements were taken from three plots and averaged. All the cropping treatments being compared have been grown alternately with spring wheat since 1995. On the graph each bar is divided into four sections that represent the water content in each of the 1-ft depth increments down to 4 feet. Alternating sections have been shaded to improve the clarity of the graph. The amounts of rain received between measurement dates are also listed.

At the start of the growing season, there was little difference in soil water content among the three treatments. The soil water content was 10.8 in./4‑ft in the plots to be fallowed, 10.4 in./4-ft in the plots to be planted to wheat, and 9.5 in./4‑ft in the plots to be planted to safflower. The trend of wetness with depth was the same in all three treatments. The soil was wettest at the 1 to 2 ft and 2 to 3 ft depths and drier above and below.

Soil in the fallow treatment both lost and gained water between successive measurement dates until August 14, after which it began to steadily lose water. Soil in the wheat treatment lost water steadily until the July 30 measurement date after which the water content remained constant. Soil in the safflower treatment lost water steadily until the August 27, after which the water content remained constant.

From the first to the last measurement dates (June 4 to September 11), the fallow plots lost 0.9 inches of water, the wheat plots lost 5.5 inches of water, and the safflower plots lost 5.2 inches of water. During the same time, 4.6 inches of rain was received at the site. Thus fallow had a net water loss of 5.5 inches, while wheat had a net water use of 10.1 inches and safflower had a net water use of 9.8 inches.

While on the last measurement date soil in the fallow plots did have an additional 4.9 inches of water carryover compared to wheat, this may not be of much benefit. Last fall (2002), fallow had a similar carryover advantage, (4.4 inches) compared to wheat. Yet by Spring 2003, that difference was only 0.9 inches. A similar situation occurred between October 2001 and May 2002 and illustrates the inefficiency of fallow at providing additional water for a subsequent crop.