Effect of irrigation frequency on rose flower production and quality

A better understanding of the effects of irrigation frequency on flower production and quality of rose plants can help to propose optimal irrigation scheduling. For this purpose, experiments were conducted on a soilless rose crop (Rosa hybrida, cv. First Red), with a closed hydroponic system, in a greenhouse located near Volos, on the continental area of eastern Greece. The plants were grown following the bending technique, on rockwool slabs. Irrigation scheduling was based on crop transpiration, and irrigation was performed whenever accumulative solar radiation outside the greenhouse reached 1600 kJ m -2 [high irrigation frequency (HIF)] and 3200 kJ m-2 (low irrigation frequency). The amount of water applied was 0·2 and 0·4 mm for high and low irrigation frequencies, respectively. Accordingly, the total water applied was equal for both cases. In order to study the effects of irrigation frequency on rose crop, measurements of fresh and dry weight of the cut flower shoots, number of harvested flowers and flowering stem's length, as well as measurements of microclimate variables were carried out. The total period of measurements ended 100 days after the last severe shoot bending (which was performed 60 days after planting). The results showed that irrigation frequency influenced cut flower fresh and dry weight, since the total fresh and dry weight of cut flower shoots measured at the end of the experimental period was about 33% higher in the HIF treatment. Statistical analysis revealed that there was no significant difference between the mean fresh or dry weight of cut flower shoots of the two treatments. As far as the number of shoots harvested is concerned, the results showed that the higher the irrigation frequency, the higher the production, as the total number of cut flowers measured at the end of the experimental period was 20·7 and 16·2 per greenhouse m -2 for high and low irrigation frequencies, respectively, namely about 28% higher in the HIF. Furthermore, the results showed that the length of rose flowering shoots was not affected by the irrigation frequency. In conclusion, it seems that the higher irrigation frequency improved the biomass production but did not affect the quality of harvested flowers. © 2005 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd