Peat-free and peat-reduced growing media for greenhouse petunia (Petunia × hybrida Vilm.) production

T.K. Haraldsen, S.M. Aurdal, T.L. Woznicki
The aim of this study was to compare various types of peat-free or peat-reduced growing media on growth and flowering of ‘Purple piruette’ petunia hybrids. In experiment 1, 30 variants of growing media, including commercial peat-based growing media, different peat-reduced and peat-free mixtures based on garden/park waste compost and wood fiber were tested. All the peat-free variants failed in producing normal, healthy plants without chlorosis. A commercial peat-reduced growing medium with peat, garden/park waste-compost and crushed rock material (0-2 mm), base fertilized with chicken manure, and similar growing media mixtures with other types of base fertilizer gave larger plants with more flowers than the peat-based reference. The highest performing mixture with the smallest amount of peat (35% wood fiber, 30% garden park/park waste-compost, 30% peat and 5% sand) gave equal results as the commercial peat-reduced growing medium. In experiment 2, further studies of the effect of peat reduction by incorporation of wood fiber and four compost types were performed. The effect of start fertilizer incorporation to the substrates was also assessed. One of the peat-free variants with compost and wood fiber gave normal plants with rich flowering but didn’t reach the performance of pure peat on plant size. The pH (H2O) of the composts seems to be a key factor for successful substrate mixtures of compost and wood fiber. The composts with highest pH gave small plants and start fertilizer had no effects on the growth. The results show that there is a potential for development of peat-free substrates based on compost and wood fiber presuming that pH (H2O) of the composts is not too high.
Haraldsen, T.K., Aurdal, S.M. and Woznicki, T.L. (2024). Peat-free and peat-reduced growing media for greenhouse petunia (Petunia × hybrida Vilm.) production. Acta Hortic. 1389, 41-50
DOI: 10.17660/ActaHortic.2024.1389.5
ash, compost, rock dust, peat, wood fiber, struvite

Acta Horticulturae