Effect of sawdust and rice husk based growing media irrigation on growth and floral quality of zinnia (Zinnia elegans)

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Abstract

Two pot experiments were carried out at the University for Development Studies, Tamale, Ghana, to determine the effects of feedstock specific composts as soil amendment and soilless media on growth and flower quality of ornamental Zinnia. Standardized composts were developed from co-composting of i) single species sawdust (SS), ii) mixed species sawdust (MS) and ii) Rice husk (RH) feedstock with poultry manure in volumetric ratios of 2:1. In the first experiment, the three standardized compost types were mixed with soil in 1:1, 1:2 and 1:3 ratios.  In the second experiment, the SS and RH based composts were each mixed with rice husk biochar in volumetric ratios of 1:0, 1:1, 1:2 and subjected to half (0.1125 mm) and full (0.225 mm) irrigation regimes. The results showed that 1 part MS compost + 3 parts topsoil improved growth of Zinnia by increasing plant height and fresh and dry biomass. The 1 part of RH compost + 2 parts topsoil increased flower diameter whiles the 1 parts of SS compost + 3 parts topsoil produced plants with the shortest flower stalk. The 1 part of RH compost + 2 parts rice husk biochar soilless media also produced the tallest plants with the widest flower head diameter. The results of our study have shown that composts and soilless media developed from variety of sawdust, rice husk and biochar can be used to improve growth and modify the flower quality of Zinnia elegans. These substrates, therefore, have a great potential for use in the production of quality composts and soil amendments for ornamental plant production in the tropics.