Reducing peat in substrate mixture formulations for press pots using the Taguchi method

• Published in: Scientia horticulturae Vol. 295; p. 110838
• Main Authors: Tietjen, Sarah, Graubner, Ines, Sradnick, André
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-03-2022
• Subjects: Compost; Growing media; Nitrogen; Nursery; Peat substitution; Rice husks; Sawdust; Compost; Peat substitution; Rice husks; Nitrogen; Sawdust; Growing media; Nursery
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/j.scienta.2021.110838

•Peat was successfully replaced by 50% in press pot substrates.•Fibrous materials positively influenced the density and stability of press pots.•N supplements are needed to balance N immobilization.•Taguchi design reduced sampling effort and enabled an effective impact analysis.
The need to substitute peat in growing media has become an urgent issue. Approximately one-third of European horticultural peat consumption occurs in vegetable production, where seedlings are cultivated in press pots. More research is needed to detect suitable, high-quality peat substitutes that provide the needed nutrient content, malleability and form stability. Mixtures of several raw materials can balance and mitigate negative effects in peat-reduced substrates; however, optimizing those mixtures may require considerable analytical effort. The Taguchi experimental design allows for a reduction of experimental trials as well as a minimization of variance. It therefore can be considered a time- and cost-saving alternative to classic experimental designs for identifying optimal mixtures. For this study, nine peat-reduced substrates (orthogonal array: L9, 34) were created, with different proportions of green compost, bark compost, sawdust and rice husks constituting 50% of these mixtures. Several biochemical, physico-chemical and physical properties were tested to assess the substrate qualities. Green compost affected the salt content, stability and bulk density of the substrates, whereas bark compost influenced nitrogen dynamics and substrate pH-values. With respect to their smaller overall proportions (0–20%), the added fibrous materials positively influenced the density and stability of the press pots. Even though N was immobilized in the peat-reduced substrates, low salinity and pH-values as well as improved stability make them promising for the creation of high-quality press pot substrate mixtures containing less than 50% peat. The “robust” Taguchi design might be a useful tool to evaluate the effects of different mixtures of up to four components with a low sample size effort.