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THECOMMERCIAL GREENHOUSEGROWER • JULY 2017
GROWINGMEDIA •
NEWAPPROACH
COULD IMPROVE DIVERSITY
the northof Europe, though some of the smaller family
farms inSouthernEuropemay look for an even longer
useful life than this,” he adds. “Themediamust therefore
maintaingood air porosity over this period.
Dependingupon its size, apottedplant canbe required
tobe in the same container for amatter of weeks or a
matter of years. For youngplants themedia needs to
have a fineparticle size toprovide constant and even
moisture andnutrients to youngdelicate rootswhile at the
same time having adequate air porosity. Older plantsmay
be required to remain in situ for several years anddespite
the applicationof nitrogen andother nutrients thephysical
quality of themediamust remainwithin anoptimum range
of air porosity andwater retention throughout this period.”
For growers sellingplants, such as protected
“Peat alternatives are not a new subject,”WayneBrough
of AHDBHorticulture commented at a recent knowledge
exchange event ongrowingmedia. The fact that reducing
or removingpeat fromorganic growingmediamixes
has been an issue for so long illustrates not only the
versatility that peat provides, but also the complexity of
the horticultural industry and the importance of growing
mediawithin it, reportsRichardCrowhurst.
AsWayne explained, the original driver to reducepeat
use has been environmental: initially focusedonprotected
finitepeat bogs and latterly, also thewider implications
of peat extractionon climate change.Whatever your
views onpeat use, there is nodoubt that a series of
newdrivers are alsomaking the industry look again at
the growingmediamixes it uses, including economic
resilience to limited resources. This canbe illustrated
by thewidespread use of coir in fruit production, which
has successfully replacedpeat, but is currently equally
dependent on a single, albeit different,material.
Inprotected salad crops, comparedwith ‘non-organic’
growing systems such as stonewool andperlite, “Organic
materials have the advantage of bufferingnutrients and
if the structure is good initially, then the growbags can
be keptmore thanone season,” points out Dr JimSmith,
ICL technical manager for growingmedia. He adds that
disposal is not aproblemwithorganicmaterials, which
are often used as soil improvers after use. “There is a
big [disposal] problemwith inorganicmaterial like stone
wool,” he adds. “Nutrient film technique, NFT, is finebut
aeration is essential andgetting levels spot on is also
essential.Most inorganic andNFT systems are for salad
production, with little found inpot plants.”
Soft fruit production is one areawhichhas embraced
organicmedia, with the use of growbags (and trough
systems) nowwidespread for strawberry production in
particular. “For soft fruit coir has been the growingmedia
of choice for several years now,” points out TomdeVesci,
ManagingDirector of Horticultural Coir Ltd. He claims,
“This is because it has a longer useful life at optimal
performance (air porosity&water retention), is easy to
dispose of and has better environmental credentials than
othermaterials, especially stonewool andpeat.
“Growbags are normally used for twoor three years in
Dr Raul Cabrera, technical partner at Horticultural Coir Ltd,
demonstrates root growth in thecompany’s 100%coirmix,
which issuitable for long termproductionof tenyearsormore.
