Effects of Maintained Substrate Water Contents on Bedding Plant Production

Abstract

Growers differ on the ideal substrate moisture content for early stages of bedding plant production. The studies presented in this thesis were conducted to evaluate the effects of substrate moisture content on growth of two bedding plant species [Impatiens walleriana (Hook.f) and Catharanthus roseus (L.)] when not thoroughly watered in at potting and the feasibility of adopting this system for producer use. The objective of the experiment in Chapter 2 was to determine the effects of substrate water content on Impatiens walleriana ‘Xtreme Red’ in early production stages and to determine depth of root growth within the container at varying substrate water contents. Five irrigation treatments [64%, 68%, 72%, 76% and 80% gravimetric water content (GWC)] were evaluated for their effect on growth of Impatiens walleriana ‘Xtreme Red’ growing in Fafard 3B potting mix. Size index, shoot dry weight, and root dry growth increased with increasing GWC. Plants in the 80% GWC treatment contained the greatest root dry weight within the bottom half of the substrate profile. In the experiments described in Chapter 3, five irrigation treatments (78%, 80%, 82%, 84% and 86% GWC) were evaluated for their effects on the growth of Catharathus roseus ‘Pacifica Deep Orchid’ and Impatiens walleriana ‘Xtreme Orange’ grown in an 80 peat : 20 perlite substrate (by vol.). Size index, shoot dry weight, and root dry weight of impatiens increased with increasing substrate GWC. Impatiens in the 86% treatment contained the greatest number of roots within the bottom half of the substrate profile. Size index, shoot dry weight, and root dry weight of annual vinca were not affected by substrate GWC. In the experiments described in Chapter 4, substrate was irrigated daily to 70%, 74%, 78%, 82% or 86% GWC during early weeks of production and placed in one of two irrigation regimes (simulated wet/dry cycle and continually wet) during the final weeks of production. The objectives were to determine the effects of irrigation regime on growth of Impatiens walleriana ‘Xtreme Orange’ and Catharanthus roseus ‘Pacifica Deep Orchid’ in early production stages when not thoroughly watered in at potting and to determine effect of irrigation regimes on depth of root growth within the container. There was a quadratic response between target GWC and annual vinca size index, shoot dry weight, and root dry weight. Annual vinca in the drier treatments (70% and 74% GWC) throughout the entire production cycle were larger compared to the plants no subjected to the wet/dry cycle. There was no difference between target GWC and impatiens size index or height. Impatiens in the driest treatment (70%) throughout the entire production cycle were taller when compared to all other treatments.