New research by Agri-Science Queensland shows nursery and cut-flower producers can actually grow plants more cost effectively using treated coconut coir potting mix, rather than the less expensive untreated varieties.
Agri-Science Queensland’s Dr Rachael Poulter said the use of coir (fibre made out of coconut husks) as a potting mix by the nursery and cut flower industries was increasing as it was affordable, sustainable, lightweight, and retained moisture.
“However, the process of treating coir results in a more expensive final product than the untreated version, so many producers have been favouring untreated coir based on price alone,” she said.
Over the past year, Agri-Science Queensland has put this to the test by researching, for the industry’s wider benefit, the productivity and cost/benefit differences between treated and untreated coir products.
“Funded through Horticulture Australia Limited, the aim of the project was to quantify differences of growth, yield and quality of gerberas grown in different treated and untreated coir products. We found there were significant effects on plant health, growth, yield and quality between those grown in treated and untreated coir. Overall, the results showed that when it comes to value for money as well as quality growth performance, treated coconut coir is the best option.”
Dr Poulter said a field trial was conducted under protected cropping practices in which three growing media were compared in terms of total productivity and flower quality parameters such as stem length, flower diameter and vase life.
“The coir supplied with no pre-treatment or buffering produced significantly fewer flowers than those grown in a pine bark/coir mix or the pre-treated coir,” she said.
“While the pine bark/coir mix produced a greater number of flowers, the flowers generally had shorter length stems than those grown in treated coir.”
A cost benefit analysis shows the higher return from better stem length outweighs the increase in stem numbers, giving a cost:benefit ratio of 2.58 for treated coir, 2.49 for untreated coir, and 2.52 for pine bark coir mix, for every single dollar spent.
“While this does not seem a large difference, when considering the number of plants a nursery or flower grower might maintain, there is potential significant cost savings from using treated coir instead of untreated coir,” she said.
“Using this cost-ratio calculation in the case of a grower maintaining 50,000 plants, the difference in revenue from using treated coir instead of untreated coir could amount to more than $60,000 per annum.
“The main conclusion drawn from this study is that favouring untreated coir products based on price alone is a false economy, she said.”
Dr Poulter said further research was recommended to assess the products over a longer time period, and using a wider range of plant species.
Agri-Science Queensland is a part of the Department of Employment, Economic Development and Innovation. Ω