Evaluation of a cocopeat-based hydroponic system for production of roses, Rosa hybrida in Naivasha, Kenya

Abstract

The cut flower industry is a key sub sector in the Kenyan economy due to its contribution to the national foreign exchange earnings. Rose flower is Kenya’s leading cut flower in terms of production and export. Much of the production of this flower occurs around Lake Naivasha which is a major source of water for production. This lake has experienced declines in the water level and water quality in the recent past due to abstraction of large volumes of water and pollution by agrochemicals from the horticultural farms situated around it. Economic and social benefits derived from the lake can therefore only be sustained if there is sustainable utilization of the lake taking the declining levels of water into consideration. Mitigation measures may include recycling of water through hydroponics cultivation system. A study was carried out from January to December 2013 at a commercial rose farm in Naivasha called Van den Berg Roses, Kenya, to evaluate the potential of a cocopeat-based system, which additionally enables re-use of the drain water in a soil-based system. Vegetative growth in both systems was assessed in terms of leaf expansion, number of leaves, stem length, chlorophyll content (represented by the measured SPAD value) and flower head expansion. The number of stems produced, weight of stems, the proportion of stem classes, rejected stems and the vase life were used to assess the production quantity and quality. The water used throughout the year in both soil and cocopeat systems was also measured. Water volume drained from the cocopeat system, the nutrients contained in the water and its quality were also assessed. Finally, the economic benefit of rose production in cocopeat substrate was calculated. Leaf expansion was characterized by an initial slow expansion rate followed by a fast expansion rate before levelling off. Maximum leaf length reached was 63 mm in the cocopeat system, while it was 60 mm in soil system; however, the difference was not significant. The number of leaves produced did not differ between the soil and cocopeat systems. The maximum number of leaves per stem was 20 for both systems. There was no significant difference in stem length of plants in cocopeat system (650 mm) and in soil system (630 mm). Measured SPAD valueon plants grown in the cocopeat system were significantly higher than for plants grown in soil (P<0.01). Flower head length and width showed no significant difference between the two