Published online by Cambridge University Press: 05 December 2011
Experiments have shown that Sitka spruce on poor soils requires relatively frequent applications of fertiliser, phosphorus being most commonly required, other deficiencies in decreasing frequency being potassium, nitrogen and, very rarely, copper. Recent evidence suggests that growth responses to fertilisers are commonest while stands are young and the green canopy is being established. Spruce has a heavy crown and in consequence nutrient demands are high prior to canopy closure. Thereafter, the annual production of foliage by spruce is no greater than that of other species of comparable growth rate and by this stage the establishment of cycles within the tree and through the litter layer enable efficient re-use of nutrients and hence the demands placed upon the soil fall dramatically.