EVALUATION OF SELECTED POTTED ORNAMENTAL PLANTS PERFORMANCE UNDER CAPILLARY WICK IRRIGATION AND FERTILIZER APPLICATION METHODS

Abstract

Ornamental horticulture industry is a major industry in the world, comprising a complex group of enterprises which consume a lot of water. Water resources are limited all over the world and there is an urgent need to adopt effective irrigation management strategies. With 640m3 water per capita availability, Kenya for example, is classified as a water deficit country. A number of approaches are being used to enhance efficient water use and to minimize the detrimental effects of water stress in plants. Capillary Wick Irrigation System, (CWS), a subirrigation system, is an innovative technique of irrigation that is simple to install, operate and uses minimal amount of water and fertilizer. This system is not currently widely used in Kenya despite her water scarcity status. It is therefore necessary to evaluate its performance in order to determine its suitability in greenhouse potted ornamental plants production. This study was therefore carried out from May, 2015 to April, 2016 in a greenhouse in JKUAT farm, Juja, Kenya; to evaluate water use and plant growth of the selected potted ornamental plants (Epipremnum aureus, Money Plant; Spathiphyllum clevelandii, White Anthurium; Dracaena fragrans, Corn Plant; Chlorophytum comosum, Spider Plant; and Cordyline terminalis, Red Dracaena) under CWS, Conventional Irrigation System (CIS) of overhead hand watering and different fertilizer application methods in Kenya. The potted ornamental plants were grown in a medium constituted of soil, sand and manure in the ratio of 3: 2: 1 respectively, under CWS and CIS. The experiment was laid out in a split-split plot design replicated three times. The amount of water applied in the two systems was determined weekly throughout the growing period. Vegetative growth in both systems was assessed in terms of leaf expansion, number of leaves and plant height. Leaf length expansion was recorded daily throughout the growing period. Stem length and leaf number were assessed weekly throughout the growing period. The growth data (leaf length expansion, number of leaves, plant height) was subjected to Analysis of Variance (ANOVA) at 5% level of significance. Means separation was accomplished using Tukey’s test. After the twelve-month growing period of the ornamental plants, this study revealed that gross water use of the CIS was higher compared to the CWS. Gross water use for the CIS and CWS was 9725 and 3529 litres respectively. The difference was significant (p≤0.05). This was a 63.75% reduction in water use when using the CWS compared with CIS. Thus, CWS offers promising potential for water saving during potted ornamental plants production when compared with CIS, given the added benefits of water conservation and reduced nutrient runoff. Leaf expansion was characterized by an initial slow expansion rate followed by a fast expansion rate before levelling off. This study also showed that Chlorophytum comosum, Dracaena fragrans, corn and Epipremnum aureus; had better growth in terms of leaf expansion and plant height, under the CWS as compared to Spathiphyllum clevelandii and Cordyline terminalis; which performed better under CIS. However, the differences were not significant (p≤0.05). The number of leaves produced did not differ between the CWS and CIS. There was no significant difference in plant height of plants in CWS (965 mm) and CWS (935 mm) (p≤0.05). In this study, it was also observed that fertigation was the best fertilization method for the selected potted ornamental plants under CWS followed by top fertilization and then side fertilization. Therefore, CWS is suited for effectively growing potted ornamental plants without lowering their quality. Adoption of the CWS for potted ornamental plants production is therefore recommended in greenhouses and/or commercial production, since it conserves water and minimizes runoff. This would also translate to increased incomes thus improved standards of living for growers. These findings form a basis for testing the system with a wider range of potted ornamental plants, other crops and ultimately commercialization of the system for the Kenyan conditions. It is expected that this will benefit growers and conserve water as well as the environment from pollution resulting from the application of excess fertilizer.