Importance of storing growing media correctly and how to do it

25 August 2022
  • Whastsapp

While semi-bulk handling systems have simplified and improved growing media storage for many growers, ICL sales manager Adrian Thirtle-Watts explains why it’s still important for all growers to store product correctly and pay close attention to use by dates.   

During the 30 years I’ve worked in the growing media industry, I’ve seen just about every variation of growing media storage. In the early days, most growing media was sold in bags, or as bulk. 

Bags offer simplicity. Usually containing a standard peat-based product with no additives, the media was sealed away from any potential contaminants. As such, they could be stored pretty much anywhere for up to a year.  

In contrast, bulk was the complete opposite - often exposed to the elements and containing additives – such as controlled release fertilizer (CRF) and, later, Intercept (replaced by Exemptor).  

Some growers stored their growing media on the ground, often with no more than a tarpaulin or polythene sheet protecting it from rain, weed seeds and other contaminants.  Others built fairly sophisticated sheds with moving roofs; or had bulk handling bins with moving floors.  

At the other end of the scale, there were purpose-built bays with growing media harvesting equipment. More recently these have evolved into computer programmed units that identify where one load finishes and the next starts – helping ensure the media is automatically rotated. 

Semi bulk resolved many storage issues  

As the industry moved to semi bulk handling systems, many storage issues were automatically resolved.  

Big bales, or even bulk bags, offer good protection from the elements as well as wind borne seeds – although. However, once opened, growers should take care as the growing media is exposed and needs protecting. Individually labelled, these systems have made stock rotation easier to control.  

Even so, the basic principles still apply.  Growers need to understand how to store and when to use growing media; this includes awareness of use by periods and the effects of CRFs, controls, biologicals, biostimulants and sustainable raw materials. 

Bulk bulk - how to maintain quality  

Bulk product should only be stored on sound concrete, which is well drained and preferably under cover – offering protection from contaminants. 

Rain not only damages growing media structure but also adds significant weight, making it challenging to handle and can contain damaging pollutants. Leaving growing media exposed to weather, surface rain or run off from fields should be avoided. 

Leaving growing media uncovered exposes it to weed seeds, air borne spray residues and potentially damaging insects and animals. Visiting nurseries over the years, as well as bird and animal droppings, I’ve seen dead animals which have burrowed into the growing media. Not only unpleasant for nursery staff, this creates particular issues for food crops or plants sold into supermarket chains. 

When storing bulk growing media in bays, avoid unused material being left at the back.  Try to use up all existing product before a fresh load is delivered or remove and rotate to the front, once the new load is dropped. 

Take note of use by dates 

It is important to be aware of, and follow, use by dates – they are there for a very good reason.  Right back to my days with Fison’s Horticulture, we had a 21-day storage period for any mix containing a CRF. This was later extended to include Intercept, a growing media incorporated long term vine weevil control. 

There are good reasons for these storage restrictions as CRFs start to release once the environment contains sufficient moisture and reaches a certain temperature. Particularly with shorter longevities or higher rates, the EC starts to increase with potential to damage young roots. 

21 days remains good guide  

Of course, the rate, longevity, temperature, moisture content and other fertilizers - such as base feed or calcium nitrate - will differ, impacting the storage period.  However, 21 days remains a good guide and is the point at which most manufacturers, including ICL, will end any legal responsibility - regardless of additional actions the grower has taken to increase storage longevity. (Check use by period with your supplier.) 

With CRFs, temperature is one of the most influential factors. It is extremely hard to adjust once the growing media has been mixed as peat and peat-free raw materials have high insulating values. As such, if a probale is manufactured in summer - when materials are warm - moving it into a cold store will have little, or no, impact on core temperature in the short to medium term. 

Non peat raw materials 

As we transition to more ‘sustainable’ raw materials, there are additional considerations to factor into storage. Wood based products, such as bark and some woodfibre products are known to draw down nitrogen over time, other products may have higher initial ECs, as such it is recommended to use these products as soon as possible. 

ICL, as well as other manufacturers, will update storage and use by periods to account for these factors. 

Consider load size and delivery options 

We all want to maximise our load sizes, for the simple reason it makes distribution far more cost effective and, indeed, environmentally friendly. However, particularly with peat free products, consider what you need and how long you need to store it. A smaller load size, while being more expensive, may in the long run be more cost effective. 

What to do if use by date has passed 

Growing media is a major investment and nobody wants to see it go to waste. If in doubt, consult your local ICL Technical Area Sales Manager (TASM) for advice.  

Generally, we recommend taking samples for analysis - to ensure the product is safe. There may be opportunities to flush nutrients out to minimise risk, however, this should only be done taking into consideration the EC, the crop and its sensitivity. As the CRF will have reduced longevity, additional feed may be required during the cropping period.  

Be aware, once the guaranteed use by period has passed – the growing media is used at the grower’s risk. 

Don’t overlook other additives  

Increasingly ICL and others are adding controls, biostimulants and biologicals to bespoke mixes. Always consider manufacturer and label recommendations for use and storage within a growing media mix, as long storage periods will have a detrimental effect on product efficacy.  

ICL makes this information available in product information and non-standard product disclaimers but, if in doubt, please contact your local Technical Area Sales Manager or our main office on +44 (0)1473 237111