Optical Caliper for Contactless Measurement of Plant Stem Diameter

Area of Science:

• Agricultural Engineering
• Plant Science
• Sensor Technology

Background:

• Precision agriculture relies on monitoring plant parameters like stem diameter for optimal crop yields.
• Traditional measurement methods can negatively impact plant growth due to physical contact (thigmomorphogenesis).

Purpose of the Study:

• To introduce and evaluate a novel contactless device, the Optical Caliper (OC), for accurate and non-invasive stem diameter measurement.
• To assess the OC's performance compared to traditional methods in controlled and field conditions.

Main Methods:

• The Optical Caliper (OC) uses a projected light beam to cast a stem shadow onto an image sensor for diameter calculation.
• Laboratory tests compared OC accuracy with a Digital Caliper (DC).
• Field trials were conducted on tomato and cucumber plants to assess repeatability on irregular stem structures.

Main Results:

• The OC demonstrated laboratory accuracy comparable to a Digital Caliper (DC).
• Field trials showed high repeatability for the OC, ranging from 0.1-0.2 mm on variable plant stems.
• The non-invasive nature of the OC avoids thigmomorphogenic effects, unlike the DC.

Conclusions:

• The Optical Caliper (OC) is a highly repeatable, non-invasive tool for precise stem diameter measurement.
• Its performance surpasses traditional methods for monitoring soft, variable plant structures.
• The OC is a promising technology for optimizing crop yields in precision agriculture and high-throughput plant phenotyping.