Evaluation of Two Different Irrigation and Fertilizer Applications on Dianthus 'Telstar™ White' and 'Telstar™ Red'

Fertilization and irrigation are important components of greenhouse container crop production. Application method of controlled release fertilizer by topdressing or incorporating as well as hand watering vs. drip irrigation can affect plant growth and visual quality.  The objective of this study was to evaluate the effect of application method on plant quality of Dianthus ‘Telstar™ White’ and ‘Telstar™ Red’ grown in the greenhouse.  Fertilizer treatments of either 0, 10, or 20 g of 16–9–12 (N–P–K) Osmocote® Plus were applied as a topdress application or were incorporated into the media, and tap water was then used during irrigations.  Pots were drip or hand watered at a rate that allowed media saturation and some leaching. Seven weeks after planting, data was collected on plant height, width, fresh weight, number of flowers, and plant survival rates.  For all fertilizer treatments except the control, higher values were seen for drip irrigated plants for height, width, and fresh weight.  For the measured variables mentioned above, higher fertilizer treatments (20 g and 30 g) did not lead to significantly higher values except for  the number of flowers under hand irrigation using topdressed fertilizer, and fresh weight using drip irrigation for either topdressed or incorporated fertilizer for either cultivar.  For plant survival, the interactions of irrigation × treatment (P =0.037) and irrigation × cultivar (P = 0.013) were significant.  Plant survival was highest for both irrigation treatments using 10 g of fertilizer incorporated, however, for drip irrigation 20 g and 30 g of incorporated fertilizer were also not significantly different. ‘Telstar™ Red’ plants had significantly fewer plants (20%) survive under hand irrigation compared to drip irrigation or ‘Telstar™ White’ under either irrigation averaging 53% survival.