Researchers build a portable, low-cost reflectance sensor for crop health monitoring

17 Oct 2025

Precision agriculture is improving agricultural processes. Various sensors have been developed, such as spectral reflectance and transmittance sensors, multispectral canopy sensors, and passive and active spectral sensors, to enhance crop monitoring.

Building low-cost and reliable plant health-related sensors is essential in the agriculture industry. In this study, a portable, low-cost reflectance sensor for crop health monitoring was developed. This new approach helps optimize crop production and fertilizer application, and effectively manage crop planting and harvesting. It incorporates various sensors to determine crop and environment parameters effectively. Common crop parameters include leaf chlorophyll content, normalized vegetation index (NDVI), crop reflectance, nitrogen content, canopy spectrum, and other macro and micronutrients essential to crop production.

The sensor comprises a white LED source and an S1133 photodiode detector. The angle between the source and detector was varied from 30 °, 45 °, 60 °, and 90 ° to determine the angle at which it would have an optimal reflectance value. The white LED source was connected to a three-volt and 0.3-ampere power supply, while the S1133 photodiode detector was connected to an oscilloscope to measure the response voltage. Different green intensities were utilized using an RGB color scheme that imitates the color of the leaf, characterizing its health status. Reflectance intensities were calibrated using white standard reflectance. The results show that the 45 ° angle between the source and detector yields the highest R-squared value (R² = 0.958).

This study provides an overview of the effects of varying detection angles for crop reflectance sensors, which can be used to assess plant health status and help improve crop yield.

Authors: Jejomar Bulan (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University) | Jumar Cadondon (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University; Division of Physical Sciences and Mathematics, College of Arts and Sciences, University of the Philippines Visayas) | James Roy Lesidan (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University) | Maria Cecilia Galvez (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University) | Edgar Vallar (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University) | Tatsuo Shiina (Graduate School of Engineering, Chiba University)

Read the full paper: https://www.mdpi.com/2673-4591/82/1/40

Researchers build a portable, low-cost reflectance sensor for crop health monitoring

Precision agriculture is improving agricultural processes. Various sensors have been developed, such as spectral reflectance and transmittance sensors, multispectral canopy sensors, and passive and active spectral sensors, to enhance crop monitoring.

Building low-cost and reliable plant health-related sensors is essential in the agriculture industry. In this study, a portable, low-cost reflectance sensor for crop health monitoring was developed. This new approach helps optimize crop production and fertilizer application, and effectively manage crop planting and harvesting. It incorporates various sensors to determine crop and environment parameters effectively. Common crop parameters include leaf chlorophyll content, normalized vegetation index (NDVI), crop reflectance, nitrogen content, canopy spectrum, and other macro and micronutrients essential to crop production.

The sensor comprises a white LED source and an S1133 photodiode detector. The angle between the source and detector was varied from 30 °, 45 °, 60 °, and 90 ° to determine the angle at which it would have an optimal reflectance value. The white LED source was connected to a three-volt and 0.3-ampere power supply, while the S1133 photodiode detector was connected to an oscilloscope to measure the response voltage. Different green intensities were utilized using an RGB color scheme that imitates the color of the leaf, characterizing its health status. Reflectance intensities were calibrated using white standard reflectance. The results show that the 45 ° angle between the source and detector yields the highest R-squared value (R² = 0.958).

This study provides an overview of the effects of varying detection angles for crop reflectance sensors, which can be used to assess plant health status and help improve crop yield.

Authors: Jejomar Bulan (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University) | Jumar Cadondon (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University; Division of Physical Sciences and Mathematics, College of Arts and Sciences, University of the Philippines Visayas) | James Roy Lesidan (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University) | Maria Cecilia Galvez (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University) | Edgar Vallar (Environment and Remote Sensing Research (EARTH) Laboratory, Department of Physics, College of Science, De La Salle University) | Tatsuo Shiina (Graduate School of Engineering, Chiba University)

Read the full paper: https://www.mdpi.com/2673-4591/82/1/40