Decomposition of organic materials from hill soils and pastures: II. Comparative studies on the mineralization of carbon, nitrogen and phosphorus from plant materials and sheep faeces

Abstract

Four plant materials obtained from Nardus and Agrostis-Festuca hill pastures, and the sheep faeces derived from these materials were incubated at 30°C for periods up to 12 weeks. The evolution of CO 2 and the production of mineral nitrogen and phosphorus were measured: 10–20 per cent and 30–55 per cent of the original carbon was evolved as CO 2 from faeces and plant materials respectively. Of the total original nitrogen, up to 8 per cent was mineralized from faeces, and up to 25 per cent was mineralized from plant materials. Grass from monthly cut treatments decomposed more rapidly than annually accumulated grass, and mineralization was greater from Agrostis-Festuca than from Nardus. More than half of the nitrogen which was mineralized was evolved as NH 3. Throughout most of the incubation period plant materials immobilized phosphorus while between 3 and 34 per cent of the total phosphorus in faeces was mineralized. The results are discussed in relation to the role of sheep in the soilplant-animal nutrient cycle.