From point sensing to intelligent systems: a comprehensive review on advanced sensor technologies for soil health monitoring

Soil health monitoring plays a critical role in enhancing crop productivity, mitigating adverse environmental impacts, and promoting sustainable agricultural practices. This review synthesizes recent advancements in sensor system technologies, examining their transformative potential for precision agriculture. It explores three interconnected themes: (i) the significant enhancement of sensor accuracy, specificity, and field-deployability for parameters such as moisture, nutrients, pH, and temperature through innovations in material science and transducer design; (ii) the capacity of integrated platforms, including Wireless Sensor Networks (WSN), the Internet of Things (IoT), and advanced spectroscopy, to overcome the spatial and temporal limitations of conventional point-based sensing; and (iii) the primary technological and scalability challenges that must be addressed to transition these technologies from research to widespread, practical adoption. Findings reveal that advancements in microelectromechanical systems (MEMS), nanotechnology, and polymer-based sensors have markedly improved sensitivity and cost-effectiveness, enabling rapid in-situ detection of NPK nutrients and reducing reliance on laboratory methods. Dielectric-based moisture sensors (TDR, FDR) and remote sensing techniques have proven highly effective for real-time irrigation management, while ion-sensitive field-effect transistors (ISFETs) and optical systems have enhanced nutrient profiling through improved pH and EC monitoring. The integration of these sensors into IoT-enabled networks facilitates extensive, real-time data collection and predictive analytics, supporting data-driven decision-making. Despite these advancements, key challenges persist, including the need for soil-specific calibration, high costs, and limited connectivity in remote areas. The evolution of soil sensor technology is progressing from basic devices to sophisticated systems capable of detecting specific ions and biological processes. Future prospects hinge on developing durable, cost-effective sensors with universal calibration models, leveraging machine learning for predictive analytics, and employing biodegradable materials to enhance sustainability. This review underscores the pivotal role of sensor technologies in achieving sustainable soil management and highlights the interdisciplinary innovations required to bridge the gap between prototyping and large-scale implementation in global agriculture.