IoT-Based Smart Soil Monitoring and Fertilizer Recommendation System

Agricultural productivity is strongly influenced by soil health and the availability of essential nutrients. Conventional soil testing methods generally require sample collection, laboratory analysis and manual interpretation, which may delay decisions related to irrigation and fertilizer application. Internet of Things (IoT) technologies provide an opportunity to monitor important soil parameters continuously and make the information available remotely. This review paper studies IoT-based approaches for soil monitoring and fertilizer recommendation, with emphasis on measurement of nitrogen, phosphorus, potassium (NPK), soil pH and soil moisture. The reviewed approaches use sensors, embedded controllers, communication interfaces and cloud-based monitoring platforms to collect and process soil information. Particular attention is given to STM32F103C8T6 as the proposed processing controller, RS485 Modbus for sensor communication and ESP8266 for wireless connectivity. The paper also reviews existing methods, identifies limitations such as sensor accuracy, calibration, communication reliability and recommendation complexity, and discusses the role of data analysis in converting measured soil conditions into useful fertilizer recommendations. Based on the review, an IoT-based architecture integrating NPK, pH and moisture sensing with remote monitoring can provide a practical foundation for smart and precision agriculture.