Low-cost sensors and microcontrollers as irrigation management tools

ABSTRACT Water is the resource that contributes the most to crop development. However, quantity and quality need to be improved, especially in semiarid regions, which makes it important to use techniques that allow rational use, especially in sensitive crops, such as lettuce. Thus, the objective was to apply a system for monitoring soil moisture, in addition to the volume of water applied through irrigation, for rural producers in the semiarid region, using low-cost sensors to cultivate leaf lettuce under irrigation depths. For this purpose, an experiment was conducted with a randomized block design in a strip-plot scheme, with five irrigation depths corresponding to 50, 100, 160, 250, and 380% determined based on the level of water replacement used in irrigation management carried out empirically by the producer, in the control range (100%), corresponding to 190 mm, with 5 replicates. These irrigation depths were monitored for soil water content using low-cost moisture sensors (HD-38) with integrated circuits (LM 393) at depths of 0 to 20 cm and 20 to 40 cm in lettuce cultivation carried out in beds. The resistive sensor allowed accurate measurement of soil moisture after calibration. The highest lettuce production and highest water use efficiency were obtained with the 723 and 95 mm irrigation depths, respectively.