Comprehensive Review of IoT-based Smart Agriculture: Technologies, Applications and Barriers

The integration of Internet of Things (IoT) into agriculture is increasingly transforming conventional farming practices into intelligent, connected, and data-driven systems, offering opportunities to enhance productivity, and resource-use-efficiency and promote sustainable food security.This study presents a comprehensive systematic literature review of IoT-based smart agriculture, following the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA 2020) framework.A total of 203 peer-reviewed publications between 2020-2024 were systematically reviewed to examine three interconnected dimensions; IoT technologies, agricultural applications, and implementation barriers.The technological analysis covers sensing technologies, embedded controllers, communication protocols, and computing architectures with particular attention to programmable logic controllers (PLCs), ESP32, microcontrollers, and Raspberry Pi platforms, wireless sensor networks, long range wide area network (LoRaWAN), NB-IoT, Zigbee, and cloud, edge, and hybrid computing architectures in supporting data processing, intelligent analytics, and real-time decision-making approaches.Practical applications-oriented analysis identifies enormous contributions in crop monitoring, precision farming, livestock management, irrigation automation, soil health monitoring, and pest and disease management.Across these domains, we then reviewed the improving performance of IoT technologies, including crop yield increases of up to 78%, water-use efficiency of up to 64% in crop-monitoring applications, water-use efficiency improvements of approximately 21-48% in smart irrigation systems, and pesticide-use reductions of 43-82% in selected pest and disease management applications.Despite these benefits, their widespread adoption remains constrained by high-initial and maintenance costs, inadequate rural connectivity and digital infrastructure, limited technical expertise and energy, interoperability limitations, concerns of data security and privacy challenges.In response to these challenges, we examined an emerging approach, including low-cost open-source platforms, resilient and self-healing hardware architecture, energy-efficient communication protocols, solar-powered systems, ruggedized sensing devices, localized edge intelligence, and hybrid networking and computing architectures.Furthermore, we presented an integrated agricultural IoT framework that connects data acquisition, communication, computing, data visualization, and system management to illustrate how technological components can be coordinated within agricultural ecosystem.Overall, this study consolidate integrated synthesis of recent IoT developments, critically examines the relationships between technological capabilities and implementation challenges, providing a comprehensive evidence base for researchers, technology developers, policymakers, and agricultural practitioners.Its findings offer strategic insights for advancing scalable, cost-effective, and sustainable IoT-enabled agricultural systems and strengthening their contribution to long-term food security.