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The Manitoba Corn Initiative: Corn Heat Unit Evaluation

Crop Types
  • Corn
Collaborating Locations


This project will utilize data being collected on plant development and maturity from a proposed network of corn breeding nurseries and yield trials in Manitoba (proposal currently under consideration by MCGA and MAFRD) as well as the Manitoba Corn Committee trials. This data will be used to model the current predictive ability of corn heat units and provide suggestions on how to improve the system from use in Manitoba.


This project is a part of the larger Manitoba Corn Initiative - Corn Agronomy, fertility and agrometeorology. Overall objectives for the program include:

  1. Identify the best crops to grow prior to corn in a rotation
  2. Evaluate fertilization strategies for corn grown after canola
  3. Conduct an economic analysis of optimal crop rotations involving corn
  4. Identify optimum corn residue management strategies.
  5. Evaluate fertilization strategies for alternative tillage systems for corn production
  6. Evaluate the corn heat unit system for Manitoba


This was a field-based study located adjacent to Agriculture and Agri-Food Canada’s grain corn yield trials at eight locations (six in Manitoba and two in southern Alberta). Five corn hybrids with varying corn heat unit (CHU) ratings (2200, 2275, 2550, 2600 and 2700) were grown in plots alongside the yield trials. Climatic values of long-term growing season CHU accumulation are not an accurate means to determine which hybrids are suitable for production in a given area. Additional site-years of study, especially for early maturing hybrids is required to draw stronger conclusions with statistical significance. The study indicated that accumulated General Thermal Index (GTI) is a potentially better alternative heat unit for selection of corn hybrids suitable to specific regions in cold temperature areas such as the Canadian Prairies. Contrary to popular belief, exposure to cold nights did not increase the heat units required for corn to reach PM and, for one hybrid, it reduced the accumulated CHU.

Key Takeaways

  1. The difference in heat unit accumulation to any phenological development stage did not differ among the 5 corn hybrids
  2. All hybrids accumulated more CHU to reach maturity than suggested by their ratings. On average an additional 300 CHU above rating was required to reach PM
  3. General Thermal Index is potentially a better alternative heat unit for selection of corn hybrids in cold temperature areas such as the Canadian prairies.

Project Details

Principal Investigator
Dr. Paul Bullock, Dr. Yvonne Lawley and Dr. Lana Reid
Project Status
Start Date
Completion Date
Funding Partners
MB Agriculture
Total Project Cost
MCA Funding

Field Issues

  • Other