Effects of type of plug and the growing media on evapotranspiration and growth of potted carnations

Plugs have a reduced rooting volume and consequently the key issue is to obtain an adequate water holding capacity. Hydrogels have demonstrated their potential to increase water retention in the medium. The physical properties of different growing media determine the availability of water which is a potential problem for the proper irrigation management in nursery pot production. This study evaluates the effects of using hydrogel added plugs and of two growing media on the evapotranspiration (ETp) and growth of potted Dianthus caryophyllus cv. 'Mondriaan'. Plugs were grown in two different substrate mixtures: peat moss and coconut fiber. Plugs with or without the addition of hydrogel (12 g L-1) were used. At the end of the cultivation cycle the plants growing from hydrogel added plugs and then cultivated in peat moss provided the highest fresh and dry weight, and the highest number of shoots and flowers per plant. The chlorophyll content of leaves was also higher when the plants were cultivated in peat moss. The water supplied to the peat moss grown plants was 13% higher than that needed by the plants grown in coconut fiber. The use of hydrogel-amended plugs did not significantly affect the water balance at the end of the cultivation cycle. Plant transpiration was significantly higher in peat moss compared to coconut fiber, probably due to the higher water holding capacity of the former. During the drought period imposed for five days at the end of the growing period, water was lost most rapidly from the peat moss during the first two days, while in the following days dehydration was more pronounced in the pots filled with coconut fiber.