Calibration of soil moisture sensors, determination of soil water retention properties for precision irrigation based on soil water content measurements

Abstract

Water is becoming a scarce commodity. Therefore, proper water management in precision irrigation is crucial to increase productivity and reduce the cost of crop production. Precision irrigation is based on measuring the soil water content, which is often measured with dielectric sensors that measure the apparent permittivity of the soil. Although the sensors are already equipped with a factory calibration function that converts the measured permittivity into volumetric water content, the function does not work properly for all soil types. It is therefore recommended to check whether a soil-specific calibration is required for accurate soil water content measurements. Precise irrigation also requires adequate determination of soil water retention properties, which can be determined using various procedures and methods. In this paper, we presented the results of applying different approaches to determine soil-specific calibration functions using two types of dielectric sensors (SM150T, Delta-T Devices and MVZ 100, Eltratec) in different soil samples obtained from locations in Slovenia where precision irrigation is performed. In addition, the results of determining the water retention properties of the soil using different methods were also compared.

Keywords

• precision irrigation
• soil moisture sensors
• water retention properties
• calibration methods