Haines, Olivia and Dodd, Ian and Collins, Richard and Fairhurst, Sarah (2023) Evaluating alternatives to peat based growing substrates for use in ornamental horticulture. Masters thesis, Lancaster University.
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Abstract
The horticultural industry urgently needs alternatives to peat based growing media as harvesting peat depletes a huge carbon sink. Although peat is an incredibly effective growing medium, the environmental costs are incredibly concerning. Factorial experiments involving spring barley (Hordeum vulgare), rye (secale cereale), dianthus (dianthus plumaris) and petunia (petunia F1 prism sunshine) were carried out in four substrates: a high peat content potting and bedding mix, a peat and wood fibre mix, a peat free coir and wood mix, and a peat free sand and topsoil mix. The research aims to address the following hypotheses: (I)The addition of surfactants improves plant growth in potted ornamental species; (II) Ornamental species grown in peat reduced and peat free media produce a lesser biomass and overall plant health than those grown in a peat-based medium; (III) Peat reduced and peat free substrates are not able to sustain potted plants and tolerate drought stress under a deficit irrigation regime to the same extent as peat-based substrates. The addition of surfactants increased above ground dry biomass in the substrates while the high peat content mix produced the greatest biomass compared to the other substrates in the majority of instances. However, there were few instances in which the peat and wood fibre mix produced plants with a greater biomass. It was determined through measurements of leaf water potential, stomatal conductance and biomass measurements that the plants grown in the high peat content substrate performed better than those grown in other substrates under deficit irrigated conditions.