Water management in peat-reduced and peat-free growing media: the effects of different frequency and volume on pelargonium

P. Alexander, N. Bragg, I. Nevison
With increased use of peat-reduced and peat-free growing media as well as increased pressure to improve the sustainability of production, UK growers need sound advice regarding water management. Our understanding of water relations in these new media mixes needs to match our understanding of peat based systems that has been built up over many years. This experiment examined the performance of Pelargonium ‘Horizon Orange Ice’ when grown in six commercially available products, a peat based control, coir based peat-free, wood fibre (two peat-free and one peat-reduced mix) or green compost based peat-free. Five different irrigation regimes, determined by regulated deficit irrigation (presented as evapotranspiration potential (ETp) rates) were studied at two frequencies, every 24 or 48 h. Dry biomass and plant quality for all treatment combinations were recorded. When examining log-transformed dry plant biomass, there was very strong evidence (P<0.001) of differences in mean values between growing media, between water frequencies and between ETp rates. While there was some evidence of two and three-factor interactions (P≤0.05) the main effects accounted for most of the differences in mean values found in dry plant biomass. Similarly for plant quality there was very strong evidence (P<0.001) of differences in mean values between growing media, between water frequencies and between ETp rates. In general, the plants were bigger and of better quality when grown in the peat control, coir and peat-reduced wood fibre at higher ETp rates and when watered daily. It would appear that our understanding of the effects of new growing media mixes needs to develop. Implications for water use are evident but consideration also needs to be given to how these materials will interact with, and potentially partially or fully replace some chemical additives too (e.g., fertilisers and plant growth regulators).
Alexander, P., Bragg, N. and Nevison, I. (2019). Water management in peat-reduced and peat-free growing media: the effects of different frequency and volume on pelargonium. Acta Hortic. 1266, 429-436
DOI: 10.17660/ActaHortic.2019.1266.59
https://doi.org/10.17660/ActaHortic.2019.1266.59
regulated deficit irrigation, coir, green compost, wood fibre, peat
English

Acta Horticulturae