Browsing by Author "Phene, C.J."

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    Soil Matric Potential Sensor Measurements in Real-Time Irrigation Scheduling
    (1989) Phene, C.J.; Allee, C.P.; Pierro, J.D.
    Soil metric potential, a measure of the holding strength of the soil matrix for water, is a critical variable in crop yield, runoff, cvapotranspiration and irrigation scheduling. A method for real-time in-suit measurement of soil metric potential ψ,,,) has been developed and tested. The accuracy of the measurement is dependent upon the calibration of the soil metric potential sensor (SMPS) against known standard pressures and independent of salinity, temperature and soil texture. The SMPS has a linear voltage response between — 10 and —300 J/kg; and depending upon the data acquisition system used, the resolution of the soil metric potential measurement ranges from 2.5 to 5.5 J/kg. The response time of he SMPS to change in pressure plate pressures is less than 24 h between — 10 and — 100 J/kg but increases rapidly to several days for soil metric potential lower than — 120 J/kg. SMPS were used to monitor soil metric potential in field soil in real time and to control drip irrigation systems automatically by initiating irrigation when a preset threshold was exceeded and terminating irrigation cycles when the time needed to apply 1.2 mm of water had elapsed. The timing of the irrigation cycle is a function of the irrigation method used, the hydraulics of the irrigation system, the soil physical properties and the crop water requirements.