QUANTIFYING DIFFERENCES BETWEEN TREATED AND UNTREATED COIR SUBSTRATE

R. Poulter
The use of coir (coconut fibre) as a growing medium, either on its own or in various mixes, has increased throughout the nursery and cut flower industries. This is largely due to its affordability, sustainability and favourable physical characteristics. The medium is available as treated or untreated coir. The treatment process involves soaking the coir with a solution high in calcium which displaces the sodium. The sodium can then be removed by further washing with good quality water.
The treatment is a solution of calcium nitrate and sometimes includes additional magnesium nitrate therefore providing calcium, magnesium and nitrate as beneficial nutrients. It is suggested that coir substrates treated with beneficial nutrients are a superior growing medium. However, the process of treating coir results in a more expensive final product; therefore many horticultural producers are favouring untreated coir based on price alone.
This research was conducted to compare the productivity and cost-benefit differences between treated and untreated coir substrate products.
A pot trial was conducted under protected cropping practices in which three growing media (treated coir, untreated coir, bark/coir mix) were compared in terms of total productivity and also flower quality parameters such as stem length and flower diameter over a five months growing period. The untreated coir produced significantly less flowers than those grown in a pine bark/coir mix or in treated coir. The pine bark/coir mix produced a greater number of flowers, but they had shorter stems.
Cost-benefit analysis showed that the higher return (prices) from better stem length outweighed the benefit from an increase in stem numbers. In an average production system with 50,000 plants, the difference in revenue would be $ 60,000.
The results suggest that favouring untreated coir products based on price alone is based on a false economy in this instance. These outcomes can assist in the future selection of appropriate and cost-effective substrates for nursery production.
Poulter, R. (2014). QUANTIFYING DIFFERENCES BETWEEN TREATED AND UNTREATED COIR SUBSTRATE. Acta Hortic. 1018, 557-564
DOI: 10.17660/ActaHortic.2014.1018.61
https://doi.org/10.17660/ActaHortic.2014.1018.61
gerbera, cut flowers, coir, growing medium, coconut fibre
English

Acta Horticulturae