Use of an ultrasonic sensor for plant height estimation in irrigated cotton

Plant height in field crops like cotton (Gossypium hirsutum L.) have long been of great interest to agronomists and plant breeders. Canopy height sensors can replace laborious point hand sampling and enable site-specific management. Study objectives were to compare manual plant height measurements with ultrasonic distance sensor measurements in subsurface drip-irrigated cotton, and to assess the effects of nitrogen and water management. Two Honeywell 943 sensors were used weekly to estimate canopy height in a nitrogen- and water-management study in Maricopa, AZ from 2016 to 2018. Hand measurements of plant height-ultrasonic-sensed height correlation increased with growth stage with r(2) of .92 to .99 at mid bloom. Root mean square errors ranged from 0.9 to 4.0 cm. Canopy height was strongly affected by nitrogen and water treatments, starting at first square. This rapid-response ultrasonic distance sensor is accurate and has great potential as a canopy height measuring instrument in cotton.

Automated summary

The study found that ultrasonic distance sensors can accurately measure canopy height in cotton plants, with a correlation between manual measurements and sensor measurements improving at different growth stages. Nitrogen and water management had significant effects on canopy height, especially starting at the first square stage.