Growth and Water Use of Petunia as Affected by Substrate Water Content and Daily Light Integral

Abstract

<jats:p>More efficient irrigation practices are needed in ornamental plant production to reduce the amount of water used for production as well as runoff of fertilizers and pesticides. The objective of this study was to determine how different substrate volumetric water contents (θ) affected petunia (<jats:italic>Petunia</jats:italic> ×<jats:italic>hybrida</jats:italic>) growth and to quantify the daily water use of the plants. A soil moisture sensor-controlled irrigation system was used to maintain θ within ≈0.02 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup> of the θ threshold values for irrigation, which ranged from 0.05 to 0.40 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup>. Shoot dry weight increased as the θ threshold increased from 0.05 to 0.25 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup> and was correlated with the total amount of irrigation water applied over the 3-week course of the experiment. The daily water use of the petunias grown with a θ threshold of 0.40 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup> was 12 to 44 mL/plant and was positively correlated with both plant age and daily light integral. Lower θ thresholds resulted in a decrease in both leaf water (ψ) and osmotic potential (ψ<jats:sub>S</jats:sub>). A decrease in turgor pressure (P) at lower θ was seen at 11, but not 20 days after the start of the treatments. There were no significant effects of θ on ψ, ψ<jats:sub>S</jats:sub>, or P on fully rehydrated plants at the end of the study. Plants were able to survive and grow at all θs, although water at a θ less than 0.20 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup> is generally considered to be unavailable to the plants. Results show that it is possible to automatically irrigate plants with the use of soil moisture sensors, and this approach to irrigation may have applications in controlling the growth of ornamental plants.</jats:p>

Water Use and Growth of Hibiscus acetosella ‘Panama Red’ Grown with a Soil Moisture Sensor-controlled Irrigation System

“…Fluctuations in q were generally larger at the lower q thresholds, as has been described previously (Garland et al, 2012;Nemali and van Iersel, 2006;van Iersel et al, 2010). Reduced hydraulic conductivity has been observed in peat-based substrates with low water contents (Naasz et al, 2005), which slows the movement of water throughout the substrate.…”

“…In the greenhouse study, the automated irrigation system used small but frequent irrigation events to maintain q just above the thresholds throughout the course of the experiment (Fig. 1), even with changing water needs resulting from plant growth and changing environmental conditions, similar to what was observed by van Iersel et al (2010). Drying of the substrates to the q thresholds occurred between Days 1 and 8 of the greenhouse study ( Fig.…”

Substrate Volumetric Water Content Controls Growth and Development of Containerized Culinary Herbs

“…Additionally, restricting P to 5 mg·L −1 produced basil, dill, parsley, and sage shorter than plants provided with 40 mg·L −1 [5]. While cultivar selection and nutrient management are useful forms of nonchemical growth control, it may be necessary to use multiple nonchemical methods of controlling growth to achieve the degree of control required in the absence of PGRs.Reducing irrigation or substrate volumetric water content (VWC), commonly referred to as "deficit irrigation", is another effective method of controlling containerized plant growth [6][7][8]. The water available for plant uptake increases and growth is promoted as substrate VWC increases and, as such, restricting irrigation and reducing the substrate VWC can diminish turgor pressure and subsequent stem extension and growth [9].…”

“…and petunia (Petunia × hybrid Vilm.) bedding plant growth is promoted by substrate VWC and, by reducing VWC, compact plants of marketable quality can be produced [7,10]. Additionally, using regulated deficit irrigation can suppress stem elongation of flowering potted plants, such as poinsettia (Euphorbia pulcherrima Willd.…”

“…Reducing irrigation or substrate volumetric water content (VWC), commonly referred to as "deficit irrigation", is another effective method of controlling containerized plant growth [6][7][8]. The water available for plant uptake increases and growth is promoted as substrate VWC increases and, as such, restricting irrigation and reducing the substrate VWC can diminish turgor pressure and subsequent stem extension and growth [9].…”