The accompanying graph shows the soil water content for summer fallow, spring wheat, and safflower at approximately 2-week intervals during the 2004 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, 10.7 in./4-ft in the plots to be planted to wheat, and 9.4 in./4‑ft in the plots to be planted to safflower. In all three treatments, the 1 to 2-ft depth was the wettest.

      Soil in all treatments gained water by the second measurement date (June 16), then lost water by the third date (June 30). During the next two weeks, the soil in the fallow treatment gained water while soil in the wheat and safflower treatments lost water. During August, the soil in all treatments lost water. During September, soil in the fallow treatment continued to lose water, while soil in the wheat and safflower treatments gained water.

      From the first to the last measurement dates (June 3 to September 22), the fallow plots lost 0.5 inches of water, the wheat plots lost 5.0 inches of water, and the safflower plots lost 4.7 inches of water. During the same time, 5.7 inches of rain was received at the site. Thus fallow had a net water loss of 6.2 inches, while wheat had a net water use of 10.7 inches and safflower had a net water use of 10.4 inches.

¹NDSU Williston Research Extension Center, Williston, ND