FIELD PRODUCTION OF GHERKINS UNDER PLASTIC TUNNELS TO PROMOTE EARLIER AND HIGHER YIELDS

It has already been stated in previous papers of this colloquium that the pickling cucumber is a heat-requiring plant. In the northern countries of the moderate climate, like ours, the production of gherkins as field crop is strongly influenced by the weather conditions in the summer season.

In The Netherlands the weather conditions in June and July are in general most favourable for the growth and production of gherkins in the open. The number of days in the months of April till July of which the minimum temperature was 5°C or lower, respectively 10°C or lower is given over a range of years in table 1. In April and May temperatures are not only too low for vigorous growth, but mostly the crop is damaged seriously, even completely killed by night frosts. For that reason planting out cannot be started successfully until the third decade of May. Hence the main harvesting-period falls in August till half of September. The weather conditions in August are often less favourable, because of much rainfall, mostly attended with lower temperatures than in the preceding month. Roughly it may be said that for that reason the yields of the field production are too low for an economic production in at least two years out of a period of five years.