Moist, dense, chocolate-coloured peat. It may not look like much, but this soil is as precious as gold dust. Peat can take millennia to form, mainly from decomposed sphagnum moss. The rich variety of specialised plants which grow on peat, and the deep layers of waterlogged soil beneath, trap vast amounts of carbon; in fact, peatland is the one of the biggest carbon sinks on the planet. This makes peat-based compost a difficult subject for veg growers, including Riverford.
Many of you will be keen gardeners who manage to avoid peat, and may be surprised to hear that we still use it. We’ve worked hard to hugely reduce our use of peat, and have eliminated it altogether for most veg. But we haven’t yet found a successful alternative for growing salad crops. There’s just one sticking point – ‘sticking’ being the operative word.
Every year, we grow millions of salad seedlings in small blocks of compost, before using machinery to plant the blocks directly into the fields. For this machinery to work, the compost surrounding the seedling’s roots has to stick together as it’s transferred from the growing container to the ground. Not much holds together like peat, and not much provides the same nutrition for the seedlings.
In our Devon polytunnels, we’ve been trialling peat-free ‘modules’ for lettuces, onions, and tomatoes, planted by hand. Lettuce yields fell by 33 per cent, and onions by 50 per cent – but tomatoes showed real promise, with only a 15 per cent drop in yield. This winter, we’re going to trial planting lettuce and onion seedlings in biodegradable cellulose nets, which hold the loose, peat-free compost together like a plant pot. We hope this will improve our results.
The silver bullet, however, lies in the creation of a completely peat-free soil block, which sticks together for machine planting and provides good nutrition for seedlings. In partnership with Innovate UK, Delfland Nurseries, Cambridge Eco Ltd. and Coventry University, we’re working on a really exciting two-year project to develop this ideal block. Six months into the project, we’re optimistic that it will yield success.
This project is vitally important. If we’re successful, we will share our findings – and help to eliminate the use of peat not just in our own fields, but in the whole horticulture industry. Watch this space.