Soil Water Extraction For Several Dryland Crops

Dryland cropping decisions would benefit from information about soil water extraction by various candidate crops. The objectives of this experiment were to: (i) quantify average soil water extraction by depth in the soil profile for winter wheat (Triticum aestivum L.), corn (Zea mays L.), proso millet (Panicum milliaceum L.), and dry pea (Pisum sativum L.), and (ii) verify previously published values of drained upper limit (DUL) and lower limit (LL) of water extraction for each crop grown on a silt loam soil in northeastern Colorado. Soil water contents at planting and physiological maturity were measured over a 21-yr period. Average ending soil water was least at all measurement depths for wheat and greatest for millet. The greatest total profile water extraction was seen for wheat (141 mm) and the least for pea (46 mm). Soil water extraction occurred, on average, from the 0- to 180-cm profile for wheat, 0- to 150-cm profile for corn, 0- to 120-cm profile for millet, and 0- to 90-cm profile for pea. When soil water was plentiful at planting and followed by dry growing season conditions, millet extracted soil water from the entire 0- to 180-cm profile. Crop rotational sequences utilizing shallow rooted crops (such as millet and pea) that do not fully extract soil water at lower depths will allow for greater soil water availability to subsequent crops such as wheat and corn that are able to explore the lower soil profile more effectively for soil water.