Abstract
Due to the need to monitor soil water tension continuously, the instantaneous profile method is considered laborious, requiring a lot of time, and especially manpower, to set up and maintain. The aim of this work was to evaluate the possibility of using capacitive sensors in place of tensiometers with the instantaneous profile method in an area of the Lower Acarau Irrigated Perimeter. The experiment was carried out in a Eutrophic Red-Yellow Argisol. The sensors were installed 15, 30, 45 and 60 cm from the surface, and powered by photovoltaic panels, using a power manager to charge the battery and to supply power at night. Records from the capacitive sensors were collected every five minutes and stored on a data acquisition board. With the simultaneous measurement of soil moisture obtained by the sensors, and the total soil water potential from the soil water retention curve, it was possible to determine the hydraulic conductivity as a function of the volumetric water content for each period using the Richards equation. At the end of the experiment, the advantage of using capacitive sensors with the instantaneous profile method was confirmed as an alternative to using a tensiometer. The main advantages of using capacitive sensors were to make the method less laborious and to allow moisture readings at higher tensions in soils of a sandy texture.
Highlights
The availability and movement of water in the soil are important factors for crop growth and productivity, since as well as satisfying water demand they determine plant access to nutrients
With the intention of proposing a more accurate and less laborious alternative for recording soil moisture, this study proposes the use of capacitive sensors to replace tensiometers in the instantaneous profile field method, in a soil of the Lower Acaraú Irrigated Perimeter
The capacitive sensors, the data acquisition system, and the power manager used in the experiment were developed at the Agricultural Electronics and Mechanics Laboratory (LEMA) of the Department of Agricultural Engineering (DENA), at the Federal University of Ceará (UFC)
Summary
The availability and movement of water in the soil are important factors for crop growth and productivity, since as well as satisfying water demand they determine plant access to nutrients. As the soil is the main water reservoir for plants, it becomes essential to determine its hydraulic properties. Among the hydraulic properties of the soil, hydraulic conductivity is important as it reflects the ease with which water moves in a saturated or unsaturated profile. The relationship that best describes soil water flow is the Darcy-Buckingham equation (Equation 1) in which the hydraulic conductivity (K) is the proportionality constant between the flow density (q) and the total water potential gradient (∆Ψt/L). According to Equation 1, the higher the hydraulic conductivity, the greater the ease with which water moves in the soil, reaching maximum value with saturation. Movement occurs to decrease this potential, i.e. the water moves from points of greater potential towards the points of least potential
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