Impact of high air temperatures on Brassicaceae crops in southern Ontario

The yield patterns of many cool season vegetable crops were observed to be different from the gradual increase in yields that has been reported over time for corn and soybeans in Ontario. A study was conducted to determine if there was a relationship between yield and seasonal weather patterns for five vegetables (broccoli, cabbage, cauliflower, radish and rutabaga) in the family Brassicaceae. The iterative chi-squared technique was used to identify correlations between daily temperature and marketable yield. Yields of all five of the crops showed some damage due to hot weather in August. For cauliflower, cabbage and rutabaga there was roughly a 10% yield loss for every 10 d that the temperature reached 30 degrees C or above during the growing season. These results shed new insight into the mechanisms by which weather affects yield.