German scientists evaluated the use of sheep’s wool as an organic soil amendment and as an ingredient in potting mixes (Böhme et al, 2012). They used wool pellets — wool compressed into pellet shape — with no other materials added.
In the field, they found that wool pellets enhanced the growth of lettuce and tomatoes (compared to synthetic fertilizers,) but not kohlrabi. In the greenhouse, the growth of potted poinsettias was positively correlated to the concentration of wool pellets in the potting mix. Another study showed that basil and Swiss chard in containers grew better when uncomposted dirty sheep’s wool was added to peat and/or perlite potting mixes.
Another study compared the value of farmyard manure (cattle manure plus bedding), leather waste and sheep wool as fertilizers (Vončina & Mihelič, 2013). Asparagus yields were highest when sheep’s wool was added. Wool, particularly ‘waste wool,’ contained higher levels of organic nitrogen (>5 per cent) and carbon (30-50 per cent) than compost or farmyard manure.
According to a British company selling wool pellets under the brand, Slug Gone, the pellets can be used as an organic mulch. After the pellets become wet, they apparently form a mat which is uncomfortable for slugs and snails to cross. The wool mulch also reduces moisture loss, controls weeds and eventually breaks down and releases nutrient.
Sheep wool as fertiliser for vegetables and flowers in organic farming. M. Böhme, I. Pinker, H. Grüneberg and S. Herfort. ISHS Acta Horticulturae. 2012. Vol. 933. pp. 195-202; Wool-waste as organic nutrient source for container-grown plants. Valtcho D. Zheljazkov, Glenn W. Stratton, James Pincock, Stephanie Butler, Ekaterina A. Jeliazkova, Nedko K. Nedkov and Patrick D. Gerard. Waste Management. July 2009. Vol. 29. No. 7. pp. 2160-2164; Sheep wool and leather waste as fertilizers in organic production of asparagus (Asparagus officinalis L.). Andrej Vončina and Rok Mihelič. Acta agriculturae Slovenica 2013. Vol. 101. No.2. pp. 191-200.
More on wool pellets
Ranchers in Utah are capitalizing on the value of wool. At Wild Valley Farms, wool waste is transformed into “Wool Pellets.” The fact that ‘waste wool,’ not high-quality wool, is used is significant for a few reasons. This is a waste product that would otherwise be burned, put in a landfill or discarded. Waste wool comes from the belly and rear ends of the sheep — wool too soiled to be of great use for clothing but with an extra hit of nitrogen from dung and urine, perfect for gardens. Moreover, the new business helps farmers get a bit more use and/or revenue from a waste product.
The wool pellets have a nutrient content of 9-1-2 NPK, as well as calcium, magnesium, iron, sulphur and micronutrients. They can also hold twenty times their weight in water. Wild Valley Farms, which ships to Canada, recommends wool pellets for use in potting mixes. In Europe, waste wool is also used as a soil amendment and mulch for slug control.
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- Janet Wallace