Ground-based remote sensing system for irrigation scheduling

The Penmane-Monteith (PM) equation is the best-known approach to estimate evapotranspiration from meteorological data on a daily basis. Limited information is available on an hourly basis, mostly because of the requirement for the parameterization of aerodynamic and canopy resistance (ra and rc, respectively), which are difficult to estimate. The objectives of this study were a) to develop a new remote sensing approach to estimate rc and ra from the output of an infrared radiometric system; b) to include rc and ra in the PM equation to calculate evapotranspiration (ET) for irrigation scheduling; and c) to formulate a numerical model that solves the changes in soil water profile with time using a onedimensional Richards' equation (RE). The integration of the time-dependent changes in the soil water profile provided the effect of irrigation on soil water balance. Infrared radiometers and a conventional meteorological system were stationed on top of a linear move irrigation system. The output signals were collected remotely in a personal computer (PC) that was equipped with specific code to solve the PM equation for ra and rc, which were then used to calculate the water requirement of the plants. The software used the actual ET as a boundary condition for the instantaneous calculations of the soil water balance components based on the hydraulic properties of the soil in Western Negev, Israel. Currently, all components that are required to improve irrigation management are controlled remotely, including the automatic data collection, models, hardware and software.