In pot trials, where very acid Sphagnum fuscum peat has been used as a growth substance, a finely ground but chemically untreated apatite concentrate has given a noticeable phosphorus effect for pine as well as for oats. Even a scarce liming has significantly diminished the phosphorus effect and a satisfactory liming has altogether stopped it. Apatite may be a suitable phosphorus fertilizer in forest manuring on bog peat soils. The carbonate included as an impurity in apatite may also be beneficial. By the use of not readily soluble phosphorus fertilizers one may diminish the possibilities of phosphorus entering water systems; this should be taken into consideration when the areas to be fertilized are very large.