An energy based indicator of plant health

Principal Investigator

Clarence Swanton & Roydon Fraser

Research Institution

University of Guelph / University of Waterloo

External Funding Partners

This project was funded in part through Growing Forward 2 (GF2), a federal-provincial-territorial initiative. The Agricultural Adaptation Council assists in the delivery of GF2 in Ontario.

Project Start

April 2014

Project End

October 2017


  • Determine if surface canopy-air temperature differential will increase as early emerging weeds are controlled.
  • Determine if surface canopy-air temperature differential will increase as the amount of nitrogen applied to corn is increased to an optimum level.
  • Determine if, as crop plants mature, the surface canopy-air temperature differential will decline, i.e. become more similar to air temperature.
  • Develop a commercial prototype sensor based on the results of above objectives.


  • The development of new crop stress detection technology with direct application to precision agriculture, including precision applications of nitrogen or herbicides.
  • The enhancement of on-farm profitability while reducing the potential impact of agricultural practices on the environment.

Scientific Summary

Crop surface temperature is extremely important when it comes to crop health because of the amount of exergy received by the plant from the sun. “Exergy” is a term used in thermodynamics to label the maximum work that a system can perform on moving from a given state (i.e., crop is stressed) to a state of equilibrium (i.e., crop is healthy) within its environmental surroundings. Applying this thermodynamic theory, it is hypothesized that healthier plants should have a lower surface temperature during the day in order to gain access to more exergy from the sun. This research is focussed on developing new technology that is capable of detecting physiological stress in crop plants caused by a nitrogen deficiency or by weed competition.

Using existing technologies, it is possible to detect differences in leaf surface temperatures based on high and low rates of applied nitrogen. A new algorithm was developed that significantly improved rapid detection of leaf temperature differences. Further refinement of this technology will enable better detection of leaf surface temperature differences in response to nutrient deficiencies or stress caused by weed competition. The results to date indicate clearly the potential to apply the concept of exergy to precision applications of nitrogen and herbicides.

Grain Farmers of Ontario is the province’s largest commodity organization, representing Ontario’s 28,000 barley, corn, oat, soybean and wheat farmers. The crops they grow cover 6 million acres of farm land across the province, generate over $2.5 billion in farm gate receipts, result in over $9 billion in economic output and are responsible for over 40,000 jobs in the province.