Soil water content and crop water use in contrasting cropping systems

Practices to improve the efficient use of water are of high relevance in rainfed agriculture. The effect of cropping systems on soil available water and water use of crops grown in a humid and temperate climate was investigated. This study was conducted at the University of Minnesota Southwest Research and Outreach Center near Lamberton, Minnesota, during three growing seasons. The treatments studied included an extended 4-year crop rotation (oat/alfalfa-alfalfa-cornsoybean) using organic inputs or high external (mineral) inputs and the traditional 2-year corn-soybean rotation, with a prairie as the control treatment. Response variables included crop yield, soil moisture monitored at 0.10, 0.20, 0.40, 0.60, 1.00, and 2.00 m depths, root length density, and crop water use. We found that alfalfa depleted more water than the other crops, including the prairie. Regardless of the extent of the rotation and the type of input, the soil water depletion and crop water use followed the same pattern: alfalfa ≥ corn ≥ oat/alfalfa ≥ soybean. For conditions in the humid and temperate climate of southwest Minnesota, the average water use of crops was 652 mm for alfalfa, 535 mm for corn, 340 mm for oat/alfalfa, and 484 mm for soybean. The average water use of the prairie was 604 mm.