Boron, phosphorus and nitrogen fertilization in Norway spruce stands suffering from growth disturbances
Silva Fennica 39(3): 351364
Growth disturbance symptoms typical of B deficiency have been reported on Norway spruce (Picea abies (L.) Karst.) trees in many parts of eastern Finland. In order to test the B deficiency hypothesis and explore the possibilities of curing the disturbed trees with B fertilization, three experiments were established in October 1999 in young Norway spruce stands growing on fertile sites in eastern Finland. All the stands contained healthy, slightly and severely damaged trees with growth disturbances typical of B deficiency (B < 5 mg kg–1). 40 healthy, 40 slightly damaged, and 40 severely damaged trees were selected as sample trees in each stand. In May 2000, the trees were fertilized with 2.0 kg B ha–1 as borax (B), 2.0 kg B ha–1 and 40 kg P ha–1 as superphosphate (B+P) or 200 kg N ha–1 as urea (N). The control trees were not fertilized (0).
The needle response to B fertilization was rapid, relatively high B concentrations being achieved already after one growing season. Boron fertilization cured the growth disorders and increased height growth within four years, but had no effect on diameter growth. The trees also recovered without B fertilization, but to a lesser extent compared to the B fertilized trees. Compared to the control, boron fertilization increased the height growth in all the disorder classes, i.e. 5, 17 and 19 cm yr–1 for healthy, slightly and severely damaged trees, respectively. As the healthy trees also seemed to benefit from B fertilization, this indicates that B deficiency in fact retards height growth before any disorder symptoms become apparent in individual trees. Compared with B alone, the application of P together with B gave no additional benefit. Nitrogen fertilization alone appeared to have a detrimental effect on height growth in the severely disturbed trees.
Received 22 June 2004 Accepted 25 August 2005