Hydroponics

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Ideal temperature and humidity regime for greenhouse crops

Temperature and humidity regime for peppers.

Temperature and humidity go hand in hand. Quite often increasing the one has an effect of the other. So keeping a good balance can be difficult.

The ideal temperatures at which peppers grow are between 18°C at night and 30°C during the day. The grower must make sure that temperatures do not rise above 34°C otherwise yields will decrease due to a decrease in number of fruits developing. Growth is reduced at temperatures above 34°C. The ideal relative humidity should be between 55% and 65%, the same as for tomatoes. These are ideal and cannot always be maintained, especially growing under shade cloth and conventional tunnels. There is always a trade-off between temperature and humidity.

Temperature and humidity regime for tomatoes.

The ideal temperatures at which tomatoes grow are between 18°C at night and 28-30°C during the day. Pollination takes place between 8H00 and 11H00 in the morning. The grower must make sure that temperatures are not above 34°C during these periods otherwise yields will decrease due to a decrease in number of fruits developing. Growth also stops at temperatures above 34°C. The ideal relative humidity should be between 55% and 65%. These are ideal and cannot always be maintained, especially growing under shade cloth and conventional tunnels. There is always a trade-off between temperature and humidity.

Temperature and humidity has a significant influence on fruit development during the growth season. A significant change in temperature will affect the quality of the fruit. For instance a change from a cold spell to warm spell or a sudden change from warm spell to a cold period will adversely affect fruit quality. The fruit goes either soft or cracks occur at the shoulder.

As has been mentioned, the management between temperature and humidity always results in a trade-off. Bad ventilation causes calcium crystals to form on the fruit which is often referred to as “Golden spots” and often confused with bacterial infection.

Quality tomatoes are produced when the temperature difference between day and night is at least more than 10°C (as a guide line). Day and night temperature and humidity should be the same. The plant requires the temperature difference in order to grow optimally. As soon as temperatures during the night falls below 10°C consistently, small and hollow fruit develop. The ideal is an average of 18°C with a maximum of 18°C and minimum of 12°C. Growth stops at day temperatures above 34°C. Pollen also tends to become sticky at these high levels so there is a reduction in yields. The ideal temperatures during the day are 28°C with maximum 34°C and minimum 22°C. The optimum pollination temperature is 26°C and takes place between eight and eleven in the morning. Minimum temperature for pollination is 24°C.

green pepper yield night temperature

The relation between night temperature and plant fresh weight

 

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