Plaggen is a type of soil created in Europe in the Middle Ages, as a result of so called 'plaggen cultivation', created by cutting turves of peat from an outfield area, and then using them as bedding for cattle; the slurry-soaked bedding was later spread on the arable fields as fertilizer. Over time, this created a very rich agricultural soil which could be over 1m in depth—unlike our modern arable soils, which tend to be just 30 cm deep.
In Orkney these soils were created already in the 12th to 13th Centuries, and on some islands in Shetland these methods continued to be used until the 1960s.