A comparison of Canadian sphagnum peat moss and coir

The Peat Research and Development Centre, Shippagan, New Brunswick, completed research, in April 1994, into the performance of Sphagnum Peat Moss, Coir Fibre and Green Compost as amendments in sandy and clay soils for the growth of tomatoes and impatiens. The research, which compared a variety of amendment blends, took place over approximately three months and was carried out by three independent growers.

Results showed that while compost and coir, in various blends with sandy or clay soil, performed nearly as well as peat moss under certain conditions for a specific plant, none worked as well as peat moss under all conditions and could be considered a universal soil amendment.

Peat moss versus coir

Sphagnum peat moss out-performed coir in several critical areas:

1. Growers said coir was difficult to handle since it must be wet when used. However, the packages are easy to handle and store.
2. Coir performed well in some applications. It did not, however, achieve good results in all blends in both soils for both plant types. In fact it delivered the worst results in growing tomato plants when blended 30 percent coir with 70 percent sandy soil.
3. The overall best tomato and impatiens plants were grown in both soil types amended with peat and lime.
4. Peat moss costs significantly less than coir.

Peat moss versus green municipal compost

Sphagnum peat moss also performed favourably to compost. In fact, adding sphagnum peat moss to compost improved the compost’s performance as an amendment under all conditions.

1. In clay soil tests, the best tomato plants grew in the blend made of 50 percent clay soil, 35 percent peat moss and 15 percent compost.
2. In sandy soil tests, the best tomato and impatiens plants grew in the blend of 50 percent sandy soil, 35 percent peat moss and 15 percent compost.
3. The worst overall tomato and impatiens plants were grown in 70 percent clay soil with 30 percent compost, and in unamended sandy soil.
4. The worst results in clay soil for both tomatoes and impatiens came in the blend composed of 70 percent clay soil and 30 percent compost.
5. Sandy soil amended with 30 percent compost produced the worst impatiens.
6. Compost is the least expensive and readily available.