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The Response of Sitka Spruce to Sulphate of Ammonia 15difficult. In addition, serious nutritional problems have been encountered.The need for phosphate fertilization of trees on peat atplanting time is firmly established (MacDonald, 1945; Zehetmayr,1954; O'Carroll, 1967; Meshechok, 1968). At present, ground rockphosphate (G.N.A.P.) is applied operationally in Ireland at 627kg/ha (91 kg P/ha) to new plantations, and also, under certaincircumstances, as a second application to existing plantations wheregrowth is considered unsatisfactory.On blanket bog in Ireland, a single initial application of phosphateis insufficient to meet the nutrient demand of the crop for the wholerotation (Jack, 1965; O'Hare, 1967a). The smaller the application,the shorter will be the period during which growth is maintained(O'Carroll, 1972), particularly with Sitka spruce. Numerous instancesof check or growth stagnation have been reported some years afterfertilization of crops in Britain and Ireland (Parker, 1957; Parkin,1957; McConaghy et a!., 1960; Dickson, 1965; O'Hare, 1967a).This condition is often associated with low concentrations of foliarnitrogen. Where drainage is adequate, both growth and foliarnitrogen concentrations are usually increased by application ofphosphate (Dickson, 1965; O'Carroll, 1967; O'Hare, 1967a;Forestry Commission, 1968).The response of tree crops on peat to direct application of nitrogenousfertilizers has been inconsistent (Zehetmayr, 1954; Jack,1965; Heikurainen, 1967; O'Carroll, 1972), though significantresponses have been obtained on sites previously fertilized withphosphate (O'Hare, 1967a; O'Carroll, 1972). Nitrogen, withphosphorus and potassium, has given strongly improved growth inFinnish experiments (Heikurainen, 1967). Similar results wereobtained with young pines in Sweden (Holmen, 1967). In the latterexperiment, a second application of nitrogen, made three years afterthe first, produced a further response.The purpose of this experiment was to examine the effects ofS/A and G.N.A.P. at high levels of application, on Sitka spruce. Inthis paper, results from the initial four year period of investigationare presented.EXPERIMENTALThe experiment was located at Glenamoy State Forest, situatedat Glenamoy in north west Co. Mayo. This is part of the low levelblanket bog (Barry, 1969) described as climatic peat by Gardinerand Ryan (1969). The climate of the area is extreme maritime; annualrainfall is 1,400 mm, distributed over 270 days. The wind climate isvery severe with gales in almost every month. The Schoenus nigricans