Effects of nitrogen and sulphur "stress" treatment on soil acidity and growth response of a Scots pine stand

In the early 1990s, revitalization fertilization experiments were established in Finland to investigate the possibilities of mitigating the effects of acidifying deposition. Annual treatments (ammonium sulphate) equivalent to 5-fold annual N and S deposition were also included during 1991-2000. The results presented here are from a replicated experiment in a Scots pine stand growing on a relatively infertile, coarse-textured soil in southern Finland. The N + S treatment strongly increased stand growth and litterfall production, indicating that the pines were still suffering from a serious shortage of nitrogen. There were no indications of nitrogen saturation, and no signs of nitrification. The serious leaching losses of Ca and Mg from the surface soil appeared to be primarily due to the addition of large amounts of sulphate. According to the results from the control plots, levels of acidifying N and S deposition in southern Finland had not been high enough to cause a threat to site fertility through soil acidification.