Reducing turbulent transfer to increase water-use efficiency | Reducing turbulent transfer to increase [crop] water-use efficiency [Windspeed modification]
1974
Hagen, L.J. | Skidmore, E.L.
Because of limited precipitation in the Great Plains, it is necessary to increase crop water-use efficiency (WUE) to increase crop yields. However, to understand how windspeed affects WUE, both the energy budget and photosynthesis rate must be considered. On the leaf scale, an incremental change in windspeed changes transpiration most at windspeeds less than 100 cm sec-1. Increasing windspeed may increase, decrease, or have no effect on transpiration, depending upon stomatal resistance of the leaf. High WUE often is associated with small leaves, which have significant stomatal resistance. On a canopy scale, the transfer of sensible heat to the surface (advection) is a significant source of energy used in evapotranspiration (ET). The amount of advection varies with season, crop, and location in the Great Plains, but in some crops a third of the energy used in ET comes from advection. In such cases, reducing turbulent exchange with the atmosphere should significantly increase WUE. Using shorter crops or sheltering a crop with windbreaks or a few interspersed tall plants can reduce turbulent exchange with the crop. To realize the full potential from reducing turbulent exchange, crops must be adapted specifically for a shelter environment. Such adapted plants would maintain high WUE in shelter to conserve water until needed for critical growth periods and would not grow tall enough to induce lodging. Adapted tall plants are also needed to provide shelter. These should be compatible with the sheltered crop, produce little shade under low light, have high WUE, and reach heights of at least 20 cm above the sheltered crop.
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