AIPH moderated a panel session at GreenTech to discuss sustainable growing media solutions and industry readiness.
Creating a good mixture for the crop that’s based on locally-sourced raw materials will be a top consideration for growers as they move towards peat-reduced and peat-free substrates.
This was the takeaway message from a discussion entitled Sustainable Growing Requires Sustainable Substrate and moderated by AIPH’ secretary general Tim Briercliffe.
The discussion took place on the third and final day of this year’s international GreenTech Amsterdam trade show on June 13 (2024) and featured guest speakers Dr Van Nguyen, researcher – growing media at the Netherlands’ Wageningen University & Research, Gracie Barrett, technical manager of the Farplants Group – one of the largest growers of container ornamental plants in the UK, Nedeljko Basic, commercial director at Finland-based substrates supplier Kekkilä-BVB, and Henri Potze, CEO/owner of Greenhouse Sustainability BV, which supports the industry in reducing and calculating its environmental footprint.
Van Nguyen from Wageningen revealed that global demand for new growing media is expected to increase to 283 million m by 2050 – a figure that is some four times larger than the volume we currently have available to us. To that end, a large amount of new and growing media materials will be required in the future. The team at Wageningen has therefore identified and is assessing the viability of five groups of potential new growing media, including acrotelm (vegetative growth on peatland, mainly sphagnum), modified wood/bark made from woods such as pine or cedar, biochar, made from different materials, plant fibre from grass plants like reed canary grass, and pre-mixes, where two or more different components are combined.
When Briercliffe asked Nguyen if there is an alternative substrate that offers the most exciting and best opportunity for growers – or if the solution is always going to be a combination of different types of growing media, she replied: “I think we should pay attention to all of them so that we can create a good mixture for a certain application. It also depends on the growers’ location as well. For example, if someone is located in Asia, I would say coir is best for them – but in America, where you have a lot of forests, your focus would be on the wood-based materials. But you should have the right mixture so that you can create the right condition for the plants.”
Briercliffe noted: “So the solution is probably going to be a local solution. So, it’s not going to be the same for everyone. But, of course, that makes it challenging for the industry – but that is part of what makes it sustainable.”
In a similar vein, Nedeljko Bašić from Kekkilä-BVB asserted: “The location of the grower and also the production locations of the [substrate] supplier is really important”. The firm has a system whereby it ranks each material according to its “Future Fit” score. This, he said, is based on whether or not a material is local and other factors such as climate resilience, circularity (such as whether the material is a waste product/biproduct from another industry), and how well the material conserves water.
Bašić added that the complexity of the growing media mixes is likely to increase in future. “We cannot expect that one material will save us and replace peat by itself,” he said. But, on a positive note, when a mixture containing different materials is well-balanced the plants can grow “even better than in a traditional substrates solution.” He noted, however, that new raw materials also have to be affordable for the grower.
In discussing her experience of Farplants’ journey towards peat-free cultivation, Barrett revealed that in the UK (where a peat ban is highly likely to come into force over the next few years), the majority of peat-free substrates tend to be made out of wood.
She said: “Wood fibre seems to be the main peat replacement. There is coir in the mixes, but there are questions about the long-term sustainability of coir [which is sourced from coconut husk fibres from countries like Sri Lanka). So, there is hesitancy within UK distributors regarding relying on coir.”
She added: “We are very reliant on wood materials in substrates, but I think one of the issues we found is that because demand is increasing so rapidly in the UK for peat-alternative materials, there is some concern about whether we have enough base materials to meet supply.”
Trialling – “absolutely crucial”
Barrett stressed the importance of trialling new substrates – describing trialling as being “absolutely crucial” because their nutrient and water management regimes can be very different to peat. “With wood-based substrates in the spring, for example, we do need to add more nitrogen-based fertilisers – and water has been a real learning curve for us. They [peat-free materials] hold water very differently depending on the wood fibre you’re using and the proportion of coir and bark [in the mix]. You do really have to be quite careful – they dry out differently, they hold water differently,” she warned.
Barrett added: “The thing about peat-free substrates is that, depending on which one you go for, they can be completely different in their physical and chemical properties. You really need to match a substrate to your production system and to your crop. And the only way you can do that effectively at the beginning is by trialling different substrates in your production and collecting meaningful data on the differences – and what that might mean for crop production going forward.”
“That was really the first step for us at Farplants – it’s been quite a complex and labour-intensive process, but I don’t see any other way of doing it to get effective results.”
Nguyen said that microbes in new growing media tend to use up the nitrogen from the fertiliser. She, therefore, advised growers to add base and slow-release fertilisers to the mixes. She also warned that new substrate material can have a high pH that can affect nutrients such as iron – but that this can be rectified by adjusting the nutrient solution and by adding a chelate.
Bašić stressed that the greater the change in the mixture, the more the growing regime will change. “If you change it slightly – say, 30 per cent of the mixture, you may just need to adapt the irrigation system. But if you change 70 per cent of the mixture you’ll need to also be aware of pH management and fertilisation.”
The need for data and global standards
Meanwhile, Henri Potze highlighted the need for an industry-wide (and, arguably, global) standard for measuring the environmental footprint of such materials. In fact, the lack of standardisation and collated information was identified as a problem that needs resolving in this area.
For example, when a member of the audience asked Barrett how data could be better shared between growers and companies, she replied: “In the UK, this is a big problem. We don’t have a good data set or a good understanding of how peat-alternative materials perform. I think we have some quite large questions about the overall environmental impact of peat-free substrates. We know that they can lead to more nutrient loss because we know we need to use more fertilisers. Does that equate to them being in more or less environmentally sustainable? It is quite difficult to be able to answer these questions … I think it relies on manufacturers, growers, and researchers coming together somehow. It’s something that needs to be looked at by the industry as a whole certainly.”
Nguyen noted that the Wageningen team is developing a calculation model that will be able to predict the physical and chemical properties of the different materials that are mixed – and calculate how much base fertiliser should be added into a certain mixture so that enough the starting nutrition is supplied for the plant.
This article was first published in the July-August 2024 issue of FloraCulture International.
