In November a new one-year field lab started, looking into eliminating peat from propagation using growing media blocks. It builds on previous work funded by Innovative Farmers and The Pebble Trust to develop a peat-free growing medium suitable for producing propagation blocks for vegetable and salad transplants. The project involves three growers, based in Fife, Perthshire and Moray, with research support from SRUC (Dr Robin Walker) and project management from Earthcare Technical (Dr Audrey Litterick).
The general feeling amongst growers experimenting with the manufacture of peat-free growing media is that it is very difficult to get the textures and physical properties required for producing blocks on any scale without peat. If the group is successful in producing a substrate which has suitable chemical and physical properties, the impact on the sector could be significant, as it would allow commercial growers to produce their own growing media, whilst also eliminating peat and plastic from the propagation stage.
The trial will build on previous work, which compared five peat-free growing media recipes for seed sowing based on locally sourced feedstocks in order to determine which were most suitable for making propagation blocks for raising seedlings (as outlined in the criteria above).
The aim is to eliminate the use of peat and minimise the use of plastic in the propagation stage of vegetable production, through the use of nursery-produced growing media blocks based on “hot bin compost”, soil, leaf mould and other constituents. The propagation blocks will:
The three trials hosts will begin making compost in November 2023, with a view to making growing media in spring 2024 which can be used to form blocks for vegetable transplants in that same season. The growing media will be tested at a UK laboratory for a series of key quality indicators and performance of the growing media and the vegetable/salad transplants will be assessed during the season.
There is frequent confusion surrounding the word “compost”, which has two broad meanings in the UK. The word “compost” can mean:
Definitions matter because the differences between true composts and growing media are considerable. The compost made in a well-run compost heap or hot bin may look the same as that which you might buy in a colourful plastic sack and use to sow seeds in or grow young plants in, but it is not. Home-produced compost is much too nutrient-rich for use alone as a growing medium, and the physical structure is not suitable. In fact it is chemically and nutritionally similar to farmyard manure and few people would try to sow seeds in that! True composts are best used as nutrient-rich fertilisers and soil conditioners OR as a constituent of growing media, which should be mixed with low-nutrient materials of suitable structure for the intended use and container size. Using true composts as growing media frequently results in poor seed germination, poor seedling growth and financial loss.
Future guidance notes will cover:
The project team is keen to engage with others. Growers, horticultural scientists and other interested parties are invited to sign up to receive:
To find out more and to get involved, visit the field lab portal on the Innovative Farmers website, where any farmer can join the network and find trial information and findings for free.
Research Institution: SRUC
Co-ordinator: Dr Audrey Litterick, Earthcare Technical