Humidification System for Propagating Houses

New Zealand Journal of Agriculture, Volume 87, Issue 1, 15 July 1953, Page 29

Humidification System for Propagating Houses

By

A. A. POWELL,

Storage Specialist, Department of Agriculture,

Wellington THE successful propagation of plant cuttings and grafts, especially • the more difficult subjects, in a glasshouse is often dependent on the maintenance of correct relative humidity. A simple method of maintaining relative humidity is described in this article. Similar methods have proved successful overseas. A PRESSURE water supply is usually available in a glasshouse and installation of the necessary fittings to atomise the water sufficiently so that it is readily taken up by the atmosphere is therefore simple. A water pressure of 75 to 1001 b. per square inch is required in the main water supply piping. To this water supply is connected fin. copper piping. Galvanised piping could be used, but additional filters or strainers .would be required in the pipeline to prevent scale from blocking the nozzles. A filter may be necessary in a copper pipeline also if the water supply is not perfectly clean. The copper piping may be fitted overhead along the apex of the house and could be slung on wires so that it does not restrict working in the glasshouse. The vaporising nozzles should be spaced alternately along both sides of the piping, and brass tees with flared joints, as shown in the illustration, should be fitted in the pipeline to take the nozzle. The fine gauze filter or strainer fits into the base of each nozzle. For a 20ft. x 15ft. glasshouse 6 nozzles should be sufficient, but actual requirements depend on water pressure, size of nozzle, and size of house. Nozzle sizes available are 1| gallons and 2 gallons per hour at 1001 b. per square inch water pressure. The best type of nozzle atomises the water into a very fine mist which is readily taken up by the atmosphere until it is fully saturated; that is, has a relative humidity of 100 per cent. The humidity can also be controlled as required, thereby creating ideal propagating conditions for a range of subjects. Control of Humidity The automatic control of high relative humidity conditions would be difficult. A clock switch and solenoid valve

could be fitted to turn the water on for a few minutes every hour, but this equipment is expensive. A manual control valve or water tap by which the water can be turned on and off at intervals should be all that is necessary for most propagating houses. From the following approximate costs of materials individual requirements can be readily estimated: Brass tees with flared couplings, 7s. 6d. each; fin. copper piping, Is. 6d. per foot; nozzles of 1| to 2 gallons per hour size with filters, £1 each. The cost of materials for a 20ft. x 15ft. glasshouse would be about £lO.