Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 1997
Publication Date: N/A
Technical Abstract: Plant available water (PAW) is usually considered to be the water between field capacity and wilting point within the root zone. The difficulty with this description of PAW is that field capacity is only defined for soils with no impeding layer or water table at a shallow depth, and that the description ignores the upward water movement (UW) into the root zone from a shallow water table (WT). The objectives of this study were to develop a better description of PAW and to relate to crop yield variability within a field in central Iowa. We monitored soil water content, tension, water table depth, evapotranspiration, rain, and variable crop yield over four growing seasons. Corn (Zea mays) and soybean (Glycine max) were grown in rotation, with both crops present each year. UW was calculated from the water balance and related to mean WT depth. PAW included terms for both UW and soil water storage. Calculated PAW did not explain all of the crop yield variability because there was not a term for flooding stress.