Calibration of Granular Matrix Sensors for Irrigation Management

Abstract

Granular matrix sensors (GMS) represent an alternative technology for measuring soil water to schedule irrigation. When GMS were tested by drying them to measure changes in electrical resistance with decreasing water content, their resistance response to drying in air in an oven was similar (t = −0.87, 134 df) to that for drying in a field soil, with a response curve that suggested GMS could be used to measure soil water potential (Ψ). Granular matrix sensor meter readings were compared with tensiometer, neutron probe, and gravimetric measurements of soil water in the root zone of potato (Solanum tuberosum L. cv. Russet Burbank) grown in silt loam. Measurements with GMS were closely related to soil water potential measurements and to soil water measured gravimetrically or by neutron probe. Meter model 30KTC, as supplied by the manufacturer, when calibrated against tensiometers, had a linear response represented by the equation y = −6.44 − 0.738 x, where y = Ψ J kg−1), and x = 30KTC meter reading (dimensionless units) of GMS, with r2 = 0.89. Granular matrix sensors were used to monitor transitory soil water stress treatments in an experiment to determine potato response to water stress.

Irrig-OH: An Open-Hardware Device for Soil Water Potential Monitoring and Irrigation Management

“…This is achieved by using suitable calibration functions. In recent decades several authors have developed different calibration curves for the Watermark 200SS sensor (Eldredge et al, 1993;Thomson et al, 1996;Shock et al, 1998;Leib et al, 2003;Intrigliolo and Castel, 2004). Allen (2000) stated that a combination of three different functions, each one valid within a specific range of output electrical resistances (R ≤ 1 Ohm; 1 Ohm < R < 8-Ohm; R ≥ 8 Ohm, respectively) produces the best result, providing reliable SWP estimates up to values of À200 kPa (Nolz et al, 2013).…”

Iwcmse

“…Sensor networks are being deployed for crop water management [26], irrigation management [25] [27], waste water management [31] [30] and to construct analytical methods for reliable water distribution [32]. Sensors are being placed in municipality water networks for detection of contaminants [24].…”

Respuesta agronómica y fisiológica del almendro al riego deficitario. Indicadores de estrés hídricos

“…Son sensores formados por una matriz granular y miden indirectamente el potencial matricial del agua en el suelo a partir de su resistencia eléctrica. La matriz granular que va fijada a un soporte de metal o plástico lleva insertados dos electrodos (Eldredge et al, 1993). La resistencia eléctrica entre estos dos electrodos varía en función de la humedad del suelo.…”

“…Las lecturas pueden ser tomadas con un lector manual o bien de forma automática y continua mediante el uso de dataloggers (Phene et al, 1971;Campbell, 1988;Campbell et al, 2006). La información proporcionada puede servir para el control y revisión de dosis y frecuencias de riego establecidas por otros métodos (Eldredge et al, 1993), o bien, ser directamente responsables de la apertura y cierre de válvulas de acuerdo a valores consigna definidos en estudios previos (Cohen et al, 2001;Intrigliolo y Castel, 2004).…”

“…Las principales ventajas son: bajo coste, no requieren mantenimiento, medidas en el mismo sitio, miden tensiones mucho mayores que los tensiómetros, etc. Y como desventajas: lenta respuesta a los cambios de humedad del suelo, muestran fenómenos de histéresis, influencia de la temperatura, pueden requerir calibraciones puntales (Eldredge et al, 1993;Thompson et al, 2006), existe cierto riesgo de que con el tiempo el yeso se deshaga, pequeña zona de influencia del elemento sensor, etc.…”