Substrate Water Content and Fertilizer Rate Affect Growth and Flowering of Potted Petunia

Abstract

<jats:p>Rising concerns over environmental impacts of excessive water and fertilizer use in the horticultural industry necessitate more efficient use of water and nutrients. Both substrate volumetric water content (θ) and fertilizer affect plant growth, but their interactive effect is poorly understood. The objective of this study was to determine the optimal fertilizer rates for petunia (<jats:italic>Petunia</jats:italic> ×<jats:italic>hybrida</jats:italic>) ‘Dreams White’ grown at different θ levels. Petunia seedlings were grown at four levels of θ (0.10, 0.20, 0.30, and 0.40 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup>) with eight different rates of controlled-release fertilizer (CRF) (Osmocote 14-14-14; 14N–6.1P–11.6K; rates of 0 to 2.5 g/plant, equivalent to 0 to 6.25 kg·m<jats:sup>−3</jats:sup> substrate). Shoot dry weight increased as the CRF rate increased from 0 to 1.67 g/plant but decreased again at even higher CRF rates. The effect of CRF rate on growth was more pronounced at higher θ. Leaf size doubled as the θ thresholds increased from 0.10 to 0.40 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup>. Flowering was reduced by a combination of high CRF rates (greater than 0.63 g/plant) and high θ (0.30 and 0.40 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup>), indicating that optimal conditions for vegetative growth are different from those for maximal flowering. These results suggest that without leaching, high-quality petunias can be grown with lower CRF rates than commercially recommended rates.</jats:p>

Growth, Quality, and Economic Value Responses of Bedding Plants to Reduced Water Usage

“…4 than it is in the vegetative stage due to energy being redirected to the reproductive organs (Taiz et al, 2015). Previous research also indicated that higher SMC combined with more fertilization increased petunia shoot growth and reduced flowering (Alem et al, 2015). Therefore, when there is a water deficit during postproduction, the competition for photosynthetic products between the root and flower could cause more flower senescence in petunia with NR-SMC, as observed in our presented research.…”

“…A water deficit during production has been shown to cause shoot growth inhibition, including reduced leaf surface area, plant height, and shoot DW. Previous studies reported that petunia, salvia, and lantana shoot DW decreased as the SMC level decreased (Alem et al, 2015;Eakes et al, 1991;Kim and van Iersel, 2009). Lower SMC inhibited the shoot growth of other bedding plant species, including vinca, carnation (Dianthus caryophyllus), angelonia, American alumroot, and gaura (Alem et al, 2015;Burnett and van Iersel, 2008;Garland et al, 2012;Guo et al, 2018;Jacobson et al, 2015;Jaleel et al, 2008;Kim and van Iersel, 2009).…”

“…Considering the economic value of potted bedding plants and the economic and environmental needs to reduce irrigation water usage, many studies have been conducted to determine bedding plants' responses to water deficits using one of two methods: holding the substrate moisture content (SMC) at a constant level or repeatedly drying down from container capacity (CC) to a lower SMC level. Lowering SMC to a constant 20% from 40% combined with lower fertilization increased flowering of petunia 'Dreams White', which increased the visual quality while lowering production costs (Alem et al, 2015). Conversely, it was reported that petunia 'Hurrah White' grown at a constant 10% SMC and impatiens (Impatiens walleriana 'Cajun Violet') grown at 30% SMC using the dry-down method reduced flower number (Blanusa et al, 2009;Chyli nski et al, 2007).…”

“…The sensor-based irrigation system was first developed by Nemali and van Iersal in 2006 to reduce water consumption by maintaining a distinct and constant SMC (Nemali and van Iersel, 2006). Previous research showed 40% SMC to be similar to the traditional wellirrigated treatment commonly used by growers for potted plant production, whereas 20% SMC was an alternative irrigation treatment that reduced water usage without detrimental effects on plant quality (Alem et al, 2015;Bayer et al, 2015;Guo et al, 2018;Jacobson et al, 2015).…”

Substrate Water Content Influences the Flowering of Doritaenopsis Queen Beer ‘Mantefon’

“…Nevertheless, water is commonly applied excessively in greenhouse production to assure complete wetness of the growing medium. Conventional irrigation with timers may result in unnecessary water application and runoff because a set irrigation volume is provided regardless of substrate moisture condition or plant water status (Alem et al, 2015). Models estimating daily water requirements from plant size and environmental factors such as daily light integral (DLI) and vapor pressure deficit (VPD) have been developed.…”