Dryland Evaporative Flux in a Subhumid Climate: III. Soil Water Influence¹

Abstract

This investigation was conducted to determine the relationship between evaporative rates of field‐grown cotton (Gossypium sp.) and grain sorghum [Sorghum bicolor (L.) Moench] and the soil water status for use in predicting evaporation on watersheds. Soil water content and soil water matric potential of Houston Black clay were measured throughout complete growing seasons for cotton and grain sorghum concurrently with measurements of the daily evaporation rate. Evaporation rates were independent of the soil water status until soil water was depleted beyond a threshold value. This threshold, termed the lower limit for potential evaporation (LLE0), was reached when approximately 18.2 cm of water had been removed from a soil profile initially wet. Another 6.5 cm of soil water was extracted at a decreasing rate before evaporation practically stopped. Evaporation rates after the LLE0 threshold was reached were practically independent of the energy available for evaporation and depended on the rooting distribution and the water movement to the roots. An analysis of the soil water transmission characteristics after the threshold LLE0 was reached showed that practically all the water extracted by plant roots was moving from the volume of soil immediately surrounding the roots. This result points out the need for growing crops with deep, dense root systems in dryland for maximum utilization of stored soil water.

Water Stress of Tallgrass Prairie Plants in Central Oklahoma

“…Deep root penetration and high root densities are important for water uptake (Kramer, 1969;Ritchie and Jordan, 1972).…”

Osmolyte accumulation: can it really help increase crop yield under drought conditions?

“…Virtually all major processes contributing to crop yield including leaf gas exchange (Ritchie, Burnett & Henderson 1972;Ritchie 1973;Sinclair & Ludlow 1986;Kuppers, Kuppers & Schulze 1988), leaf growth (Sinclair 1986;Rosenthal et al . 1987;Lecoeur & Sinclair 1996;Muchow & Sinclair 1991) are inhibited late in stage I or in stage II of soil drying.…”

Plant-available soil water capacity: estimation methods and implications

“…Despite not considering the dynamics of the soil-water-plant-environment interrelationships (Reichardt, 1988;Carlesso, 1995;van Lier, 2000), this concept has a recognized practical importance for water balance, soil drought, definition of planting times, agricultural zoning, and particularly in irrigation projects, which makes AWC a parameter of great importance in planning land use. The AWC can be understood as a soil property that indicates the duration and intensity of water deficit, with the advantage of depending mainly on the water use rate and soil physical properties (Ritchie et al, 1972;Carlesso, 1995).…”