You are here:

A nation that can't control its energy sources can't control its future. Barack Obama
  • The idea of a semi-sealed greenhouse was a natural development from the completely-sealed greenhouse that was pioneered over 10 years ago. In this Technical Update, we look at the advantages and disadvantages of a semi-sealed greenhouse system, and what the future holds.
  • Common practice is to put measuring boxes in a position that is both practically convenient and which provides representative measurements of the conditions in the greenhouse.
  • Using heat to control humidity in a greenhouse gives the advantages of a good yielding and a disease-free crop. But with energy prices rising, many growers are left wondering whether humidity control is something they can really afford.
  • What are the energy implications of using ‘pre-night’ or ‘drop’? ‘Pre-night’ is a technique used by some edible crop growers who believe that a rapid drop in greenhouse temperature just before sunset helps crop development.
  • In recent years, the accepted norm for growers of edible crops such as tomatoes, cucumbers and peppers has been to control humidity based on humidity deficit (HD). This is because conventional wisdom suggests that maintaining a minimum HD promotes transpiration, which, in turn, ensures optimised plant development and growth.
  • In our article 'Where should you position your measuring box?', we showed how relying on a measuring box placed in the traditional position at the top of a tomato crop can give non-optimised control of the greenhouse environment and lead to wasted energy.
  • Minimum pipe temperature set points are used to force heat into a greenhouse even if it is not required to maintain the required greenhouse temperature.
  • Avoiding condensation on plants is a key part of any disease control strategy. Poinsettia growers have to pay particular attention to this problem as they use a technique to control plant height called ‘Drop’. ‘Drop’ involves reducing the greenhouse temperature to as low as 12 degrees C before sunrise and is followed by an increase in the greenhouse temperature to the daytime set point within one hour after sunrise.