Seed Germination and Seedling Growth of Four Bedding Plants in Substrate Containing Coal Bottom Ash Mixed with Coir Dust

Abstract

Coal bottom ash (BA) is a by-product of coal-fired power generation and can be utilized as a growing substrate for ornamental plants. The physical and hydraulic properties of BA-mixed substrates (coir dust:BA, 10:0, 9:1, 8:2, 7:3, and 6:4, v/v) and commercial germinating media (BM2; Berger Peatmoss) were investigated, and the effects of the substrate mixtures on seed germination, seedling growth, and heavy metal concentrations (Cd and Pb) were evaluated for four common bedding plants (periwinkle (Catharanthus roseus), globe amaranth (Gomphrena globose), impatiens (Impatiens walleriana), and petunia (Petunia multiflora)). As the BA:coir dust increased, the air space rate in the substrate increased from 25.5 to 28.0%, providing the substrate with sufficient porosity. However, the container capacity and amount of easily available water decreased from 63.1 to 53.7% as BA proportions increased. In the final germination percentage and days to germination of the four bedding plants, no significant differences were detected among the substrate mixtures. Although the impatiens and petunias displayed poor growth (46–55% and 42–56% of dry weight, respectively) in the BA-mixed substrates compared to the BM2, no apparent differences in the seedling growth of periwinkles and globe amaranths were found between 7:3 (coir dust:BA) substrate and BM2. These results indicated that the BA-mixed substrates had the potential to replace the commercial germinating media. The plants grown in the BA-mixed substrates contained Cd, but it was unlikely to be derived from the BA.

Trichoderma atroviride Enhances Impatiens walleriana Hook. f Growth and Flowering in Different Growing Media

“…Coir has become one of the most commonly used peat alternative growing media constituents worldwide, at least in the last two decades [ 7 , 8 , 9 ], despite some emerging criticisms about its sustainability due to the environmental impact related to composting processes and shipping, as well as the social issues such as community infrastructure problems and human and labor rights respect [ 7 , 10 ]. It is a renewable material with optimal well-known physical–chemical properties [ 11 , 12 ], which allow the successful production of many soilless crops, such as bedding plants, including Impatiens spp., used both as a stand-alone substrate or in mixtures, starting from germination and seedling growth [ 13 , 14 , 15 ]. Coir, as organic matter, has higher microbiological activity compared to peat [ 16 , 17 ], and it has a recognized natural content of plant growth-promoting bacteria (PGPB), such as phosphate-solubilizing bacteria and indole-3-acetic acid-producing bacteria [ 18 , 19 ].…”