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The Blaney–Criddle equation is a relatively simplistic method for calculating evapotranspiration.When sufficient meteorological data is available the Penman–Monteith equation is usually preferred.
Irrigation scheduling is the process used by irrigation system managers to determine the correct frequency and duration of watering. The following factors may be taken into consideration: Precipitation rate of the irrigation equipment – how quickly the water is applied, often expressed in inches or mm per hour.
The first MPR nozzles, the MP Rotator, were produced by Nelson Irrigation in 2003, and acquired by Hunter Industries in 2007. [4] [5] [6] Since then the popularity of these highly uniform yet low application sprinklers has caused every major sprinkler manufacturer to produce their own version of an MPR sprinkler, including Rain Bird [7] and Toro.
Surge Irrigation is a variant of furrow irrigation where the water supply is pulsed on and off in planned time periods (e.g. on for 1 hour off for 1½ hour). The wetting and drying cycles reduce infiltration rates resulting in faster advance rates and higher uniformity [4] than continuous flow.
Distribution uniformity may be helpful as a starting point for irrigation scheduling. For example, an irrigator might want to apply not less than one inch of water to the area being watered. If the DU were 75% (0.75), then the total amount to be applied would be the desired amount of water, divided by the DU.
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 ...