Sphagnum soil

If you buy bagged soil today, you are most likely buying peat mixed with sand and some clay. Peat has very good properties for growing in pots, but it is classified as a fossil because it forms slowly. In Sweden we have large areas of drained peatland. When peatlands are drained, they start to decompose and the carbon stored as peat turns into carbon dioxide instead. Drained peatlands account for a third of our territorial emissions. Only a small proportion of these are cut, but when they are, they decompose faster.

At the same time, a great deal of development work is underway in making products based on other raw materials, such as coconut fiber, fibers from reeds and straw, composted bark and biochar.

With this project we want to find out if we can successfully grow sphagnum moss as an alternative to peat. Sphagnum moss grows faster than peat, experiments have shown as much as 20 cm growth per year, unlike peat which grows 1 mm in a year. The aim is to create a farm-level cultivation that can provide access to a material that improves soil mixtures for pot cultivation.

Sphagnum moss will be grown using a few different methods and then scaled up. The cultivation experiments are carried out in a pond covered by a net with irrigation from collected rainwater and municipal water. The three experiments consist of a floating raft covered with a capillary mat, a fully floating and a semi-floating sphagnum moss tray.

Sphagnum moss, which becomes peat as it decomposes, shares many of the good growing properties of peat even when it has not decomposed. However, it may also contain anti-sprouting substances which in turn may affect the ability of larger plants to grow.

We are conducting a plant cultivation experiment where we transplant tagetes, amaranth and tomato in three different soil mixtures. A peat-based planting soil, a mixture of compost soil from parks and well-broken down cow manure with straw, and lastly a mixture containing one third of fresh sphagnum moss, one third compost soil from parks and one third cow manure. We will evaluate the properties of the soils, but also the height and quality of the plants.

Results

The results of the cultivation trial with the different soil mixtures show that both our alternative soils using local resources work well. The sphagnum moss made the soil mixture more moisture retentive and this was particularly valuable immediately after repotting. But after 6 weeks, the difference between these two soils became negligible. While the peat-based soil did produce the largest plants, there may be several explanations to this. One main theory is that this is partly because the alternative soils would have benefitted from more watering. All soils received exactly the same amount of watering at the same intervals, even though the alternative soils had lower moisture-retaining capacity.

– The results show that in the future, we can reduce our dependence on peat-based soils and make even more use of our compost and cow manure soil mixtures, which only need to be transported meters instead of tens of kilometers. "It's not a working method that suits everyone, but for small-scale plant productions rather than commercial growers, this is excellent," says project manager Anders Stålhand.

The sphagnum moss cultivation is still in its early phase, and the results will be available at the earliest in the fall of 2023.

PROJECT NAME

Sphagnum soil

STATUS

Ongoing

OUR ROLE IN THE PROJECT

Project owner

PROJECT START

2023-03-01, projektlängd 10 månader