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The energy required per unit mass of water vaporized. (J g −1) L v = Volumetric latent heat of vaporization. The energy required per unit volume of water vaporized. (L v = 2453 MJ m −3) E = Mass water evapotranspiration rate (g s −1 m −2) ET = Water volume evapotranspired (mm s −1) Δ = Rate of change of saturation specific humidity ...
Given the coarse accuracy of the Blaney–Criddle equation, it is recommended that it be used to calculate evapotranspiration for periods of one month or greater. [ 1 ] The equation calculates evapotranspiration for a 'reference crop', which is taken as actively growing green grass of 8–15 cm height.
Water stress is the most ubiquitous stress factor, often denoted as K w. Stress coefficients tend to be functions ranging between 0 and 1. The simplest are linear, but thresholds are appropriate for some toxicity responses. Crop coefficients can exceed 1 when the crop evapotranspiration exceeds that of RET.
The Penman equation describes evaporation (E) from an open water surface, and was developed by Howard Penman in 1948. Penman's equation requires daily mean temperature, wind speed, air pressure, and solar radiation to predict E. Simpler Hydrometeorological equations continue to be used where obtaining such data is impractical, to give comparable results within specific contexts, e.g. humid vs ...
It is also known as available water content (AWC), profile available water (PAW) [2] or total available water (TAW). The concept, put forward by Frank Veihmeyer and Arthur Hendrickson, [ 3 ] assumed that the water readily available to plants is the difference between the soil water content at field capacity ( θ fc ) and permanent wilting point ...
[10] [11] If there existed a situation where water deficit induced lower transpirational rates without simultaneously decreasing photosynthetic rates and biomass production, then water-use efficiency would be both greatly improved and the desired trait in crop production. Water-use efficiency is also a much studied trait in Plant ecology, where ...
Crop water productivity (WP) or water use efficiency (WUE) [5] expressed in kg/m³ is an efficiency term, expressing the amount of marketable product (e.g. kilograms of grain) in relation to the amount of input needed to produce that output (cubic meters of water). The water used for crop production is referred to as crop evapotranspiration.
Evapotranspiration is a combination of evaporation and transpiration, measured in order to better understand crop water requirements, irrigation scheduling, [4] and watershed management. [5] The two key components of evapotranspiration are: Evaporation: the movement