Water use and depletion by diverse crop species on Haplustoll soil in the northern Great Plains

In a semiarid-to-subhumid region, water use by crop species can have a considerable impact on both crop production and soil landscape hydrology. Crop production following high water-using crops can be decreased while ephemeral streams and wetlands can be increased by growing lower water-using crops. Water use and soil water depletion were determined with neutron moisture meters in ten crop species (barley, canola, crambe, dry bean, dry pea, flax, safflower, spring wheat, soybean and sunflower) for two years, and measurements are presented for four of these species for one additional year. The observations were made in various species which were grown after spring wheat during crop sequence experiments. Sunflower was the greatest water user, followed by safflower and soybean. Dry pea was the lowest water user, followed in order by barley, crambe, and spring wheat. During an above average precipitation year, the depth distribution of soil water depletion among canola, dry pea, spring wheat, and sunflower was similar. In contrast, during a year of relatively low seasonal precipitation, differences were evident among the four crop species. Sunflower and canola extracted 49 percent and 45 percent of their soil water depletion, respectively, from soil depths greater than 60 cm, while spring wheat and dry pea extracted 33 percent and 27 percent of their soil water depletion from below 60 cm depth. Using a three-year dataset, it was found that water use and soil water depletion were highly correlated with seasonal precipitation, significantly correlated with median depth of water depletion and days from seeding to harvest, but not correlated with root growth parameters. As a general guide to water use by crop species, length of active growing season appears to be the most important factor.