The effect of water and nutrient availability on the productivity of Norway spruce in northern and southern Sweden

Results from two yield optimisation experiments in young stands of Norway s pruce in northern and south-eastern Sweden are presented after 10 and 9 yea rs' treatment, respectively. The aim of the experiments was to demonstrate the potential yield of Norway spruce, under given climatic conditions and n on-limiting soil water, by optimising the nutritional status of the stands, at the same time as leaching of nutrients to the groundwater was avoided. A complete mix of nutrients was supplied either once a year or daily during the growing season, in combination with irrigation. On the basis of repeat ed foliar analysis and predicted growth response the proportions and amount s of nutrients applied were adjusted annually. After 10 years' treatment at the northern site, fertilisation had increased the annual stem volume prod uction from 3 m(3) ha(-1) a(-1) in unfertilised stands to 14 m(3) ha(-1) a( -1). Although site quality initially was high at the southern site, nutrien t optimisation increased annual stem volume yield from 12 in control stands to 29 m(3) ha(-1) a(-1) in irrigated-fertilised stands, Water had a positi ve effect on stem growth in southern experiment, but no effect in the north . in all stands in which the availability of nutrients and soil water was o ptimised by combined fertilisation and irrigation, the yield of stemwood wa s similar to or surpassed the best yields obtained by conventional silvicul tural means. (C) 1999 Elsevier Science B.V. All rights reserved.