Terahertz Sensing for Agricultural Engineering: Applications and Intelligent Data Analysis

The growing demand for rapid and nondestructive sensing in precision and smart agriculture, particularly for continuous crop monitoring in controlled environment agriculture (CEA), has stimulated interest in terahertz (THz) technologies. Owing to their sensitivity to water, low-frequency molecular vibrations, and dielectric properties, THz waves provide a promising approach for probing agricultural materials. This review summarizes advances in THz sensing for agricultural engineering. The principles and characteristics of THz time-domain spectroscopy, frequency-domain spectroscopy, and imaging are first introduced, together with the major interaction mechanisms between THz waves and agricultural materials. Advances in THz data analysis are then discussed, focusing on model selection, reliability under small-sample conditions, multi-source information fusion, and mechanism-informed analysis. Applications are subsequently reviewed in seed quality and germplasm identification, soil property assessment and contaminant detection, crop water-status monitoring, stress and disease detection, and agricultural product quality and safety assessment. Key challenges include complex-matrix interference, weak target responses, limited model generalization across scenarios, and system integration. Future research should emphasize high-sensitivity sensing, mechanism-data-integrated modeling, and miniaturized online detection systems to facilitate the practical deployment of THz technologies in agriculture, including greenhouses and other controlled production environments.