© 1972 by Institute of Chartered Foresters
Nitrogen Mineralization and Organic Matter Decomposition in Scots Pine Humus
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen Scotland
Nitrogen deficiency in many northern coniferous forests is associated with increasing age of the crop and is thought to be due to a slow rate of release of available nitrogen from the organic layers of the forest floor. Practical ways of stimulating nitrogen release from this material by applications of nitrogen, phosphorus, and lime are being studied in a 40-year-old crop of nitrogen-deficient Scots pine (Pinus sylveitris L.) at Culbin Forest, Moray. Three years after lime and phosphorus treatments, and two years after the second fertilizer nitrogen application, significant treatment effects included both markedly higher pH values and increased rates of organic matter decomposition on incubation (at 30 °C for 62 days) for humus from plots given lime and higher rates of net production of mineral nitrogen on incubation for humus from plots given fertilizer forms of ammonium sulphate, urea, and ammonium nitrate. Only urea-treated humus still showed a significantly higher total nitrogen content at this time, I.54 per cent of organic matter compared with 141 per cent in untreated material.