Cardinal temperature

• Every plant community has its own minimum, optimum and maximum temperature known as their cardinal temperature.
• These critical low and high temperatures are required for better growth and development of crops.
• The three types of temperature ranges are:

1. Optimum temperature

• The temperature at which a plant functions best is called as the optimum temperature.
• The ideal temperature conditions for crop production are in the range of 31-37oC for hot season and 25-31oC for cool season crops.

2. Maximum temperature

• Maximum temperature is the one that can be tolerate without injury to crop plants. The maximum temperature tolerance varies greatly with the crop species. Above which plant growth stops.
• The tolerable maximum temperature for hot season is 44-50oC and cool season crop is 31-35oC.

3. Minimum temperature

• Minimum temperature is the temperature at which any plant can continue its activity and below which no growth occurs.
• It is approximately the freezing point of water. The growth of many of the tropical plants is retarded at 20oC and are frequently killed at 10oC.
• The tolerance range of minimum temperature for cool season crops ranges between 0-5oC and hot season crop 15-18oC.

Cardinal points of some common crops