A comprehensive review of proximal spectral sensing devices and diagnostic equipment for field crop growth monitoring

Abstract

PURPOSE: This review synthesizes advancements in proximal spectral sensing devices—including portable, vehicle-based, UAV-based, and IoT-based—for monitoring field crop growth traits. By evaluating their technical capabilities, applications, and limitations, it addresses critical challenges in scalability, data integration, and environmental adaptability to advance precision agriculture (PA) practices. METHODS: A systematic analysis of literature (2001–2024) was conducted using keywords such as “proximal remote sensing,” “spectral sensors,” and “crop growth monitoring” in the Web of Science database, yielding 1,278 publications. The performance, sensing mechanisms, and practical applications of these devices were analyzed across platforms, with a focus on their ability to estimate key growth indicators (e.g., biomass, leaf area index, nitrogen content) and resolve PA-related challenges. RESULTS: Portable spectral sensors excel in capturing high-resolution, targeted measurements but face limitations in accuracy during early crop growth stages and under complex field conditions. Vehicle-based systems enable efficient large-area scanning but encounter synchronization challenges between sensors and machinery, alongside susceptibility to environmental interference. UAV-based devices deliver rapid, high-throughput data collection but require enhanced endurance and integration with satellite imagery to achieve regional scalability. IoT-based networks support continuous monitoring but are constrained by a lack of specialized spectral sensors and insufficient durability in harsh agricultural environments. Cross-platform data fusion remains impeded by heterogeneity in data types, spatial scales, and storage protocols, while device durability, algorithmic robustness, and environmental resilience emerge as critical factors for reliable field deployment. CONCLUSIONS: Proximal spectral sensing devices hold transformative potential for multi-scale crop growth monitoring, yet persistent technical gaps hinder their widespread adoption. Future research should prioritize the development of lightweight hyperspectral imaging systems paired with advanced computational algorithms, unified frameworks for cross-platform data fusion, and durable IoT sensors tailored for harsh field conditions. Additionally, integrating UAV-based data with satellite observations will enhance regional insights, while standardized protocols and interdisciplinary collaboration are essential to bridge ground-to-space monitoring networks. These advancements will foster intelligent, sustainable crop management systems, ultimately addressing global agricultural productivity and sustainability challenges.

Plant phenotyping relevance

作物生育形質（バイオマス、LAI、窒素含量）を推定する近接スペクトルセンシング機器の性能・技術・限界を体系的にレビューしており、フェノタイピング手法が中心である。

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