A Solar-Powered IoT-Based Smart Irrigation and Fertigation Monitoring System for Chili Cultivation

Abstract

Smallholder chili production in Malaysia is frequently constrained by inconsistent manual irrigation, imprecise fertilizer application, and unreliable rural electricity supply. This paper presents the design, implementation, and seven-day field evaluation of a solar-powered Internet of Things (IoT) smart agriculture monitoring and automation system built around an ESP32 microcontroller. The system integrates an analog soil moisture sensor, an RS485 Modbus RTU soil pH probe, and two ultrasonic level sensors to continuously track water and liquid-fertilizer reservoir volumes. A closed-loop control algorithm automatically activates dedicated irrigation and fertigation pumps whenever soil moisture falls below a 40% threshold or soil pH drops below 5.5, while reservoir-level interlocks disable the pumps once liquid levels fall below 20% to prevent dry-running. A 20×4 I2C liquid-crystal display provides on-site status feedback, while the ESP32 relays sensor data to the ThingSpeak cloud platform for logging and visualization and to the Blynk mobile application for remote monitoring and manual override. A solar panel, charge controller, and 12 V/7 Ah sealed lead-acid battery sustain uninterrupted operation independent of grid electricity. Field results show soil moisture cycling between approximately 82% and 92% with automatic recovery to 80-86% following each irrigation event, soil pH remaining stable between 5.4 and 5.8, and battery voltage peaking at 13.4 V at solar noon while staying above 12.1 V overnight. Functional validation of all five sensor-actuator interlocks returned a 100% pass rate. These findings demonstrate that a low-cost, solar-sustained IoT architecture can deliver reliable, low-maintenance precision irrigation and fertigation, offering a scalable and economically feasible pathway toward off-grid precision agriculture for smallholder farmers.