Abstract
ABSTRACT Knowing the soil moisture available to plants is important for adequate management of water use in agricultural farms, with automated methods being the most accurate. However, acquisition costs are high and most of the commercially available irrigation controllers still work using pre-set times. This study aimed to develop and calibrate a low-cost automated tensiometer with high efficiency in irrigation control, based on real-time monitoring. The research was conducted at the Laboratories of Hydraulics and of Water Soil Plant and Atmosphere Relationship, which belong to the Federal University of Grande Dourados (UFGD), in Dourados, MS, Brazil, with soil classified as an Oxisol. Pressure transducers and a microcontroller were used to assimilate the pressure inside tensiometers and transform it into readings of soil water matric potential (Ψm). Thus, the calibration was carried out by comparing the different readings of the transducer and digital tension meter. Different tensions were applied to obtain a soil moisture curve, starting from the most humid point (saturated) to the driest one (oven-dried soil), collecting 20 valid points. Subsequently, the data were subjected to the normality test, with subsequent statistical analysis and regression curve models. Linear adjustments with a high coefficient of determination (R2 = 0.99) were observed, with the automated system built in this study being capable of monitoring soil water tension in real-time.
Highlights
Material and MethodsTechnology is used in different sectors, such as agriculture
Automated tensiometers can be simple to use and low cost for farmers, most commercial irrigation controllers connected by soil sensors are programmable with only fixed times
The electronic system has a high coefficient of determination between the sensor and digital tensiometer readings
Summary
Technology is used in different sectors, such as agriculture. Innovations in rural areas have pointed to precision agriculture as a common practice in the future (Lowenberg-Deboer et al, 2020). Automated tensiometers can be simple to use and low cost for farmers, most commercial irrigation controllers connected by soil sensors are programmable with only fixed times They may disregard changes in soil moisture or water potential levels. In this context, the study aimed to develop and calibrate a low-cost automated tensiometer with high efficiency of irrigation control based on real-time monitoring. Low market cost (around US$12.00), meeting the management requirements proposed in the project This sensor acts as a differential pressure sensor between two points (P1 and P2), consisting of a silicon diaphragm, which deforms according to the stress induced by the pressure of an external agent, causing an analog signal proportional to the pressure exerted on the diaphragm. Regression models were constructed to determine the linear calibration equation (Eq 3):
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