F.-W. Frenz
It is reported on a tension switch, consisting of a pottery element, plexiglass and a vacuum quickbreak switch and its application in irrigation of balcony- and window-sill plants. The water distribution is realized by a Volmatic-drip irrigation system. In the climate of Upper Bavaria and a cultivation period from early May to the end of November, the plants received water for 811 times. With a total water requirement of 43.14 litres per plant this makes 53 ml per watering operation. It is expected that the developed watering and control system will obtain importance beside the hobbyist cultivation also in greater grounds around public buildings and in horticulture.

In summer every owner of balcony-boxes and window-boxes is longing for an overflowing adornment by flowers. To reach this purpose a great number of determinations are necessary. To begin with, the species and varieties of the plants have to be selected. The next step is the planting of the boxes and finally the cultivation during the summer should be thought over. Thereby watering is one of the most important tasks.

On hot summer days it is even necessary to water several times a day. To avoid that water is running through the boxes and bothering inmates of the house or passers-by, one should not give too much water all at once. Another problem is the watering of balcony-plants during absence. Neighbours or friends, who would take care of the watering, are on vacation at the same time. This is for many persons the reason to do without a decoration at the balcony.

However, one can commit watering to an automatism. For this purpose a tension switch had been elaborated (Photo 1). The feeler consists of a pottery element, a plexiglass-tube and a vacuum switch. By the commencement of service it is replenished with water and closed by a rubber stopper. The pottery element of the tension switch is sticked in the substratum in the boxes next to a plant. While evaporating water by the plant, the soil becomes more desiccate. Reaching a certain dryness, the vacuum switch makes a contact. Now an electric current is able to open a solenoid valve at the water pipe.

The water will be distributed simpliest by a drip irrigation system, in principle constructed of a distributing pipe with inserted drip tubes or drip elements. The Volmatic-drip irrigation system proved very useful. It has been laid on balconies behind the flower-boxes, in the described example (Photo 2). For an optimal water supply, every plant gets its own emitter. A black ½ inch polyethylene tube serves as distributing pipe. The drip tubes could be inserted in the pipe by the user of the system himself with a special punch, which is delivered by the firm.

DOI: 10.17660/ActaHortic.1979.89.14

Acta Horticulturae