The effect of the acidity level of simulated acid rain, of the total nutrient concentration, nitrogen supplementary nutrition and deficits of nitrogen, phosphorous and potassium was studied as exerted on the growth and selection of vital seedlings of Picea abies (L.) Karst., Larix decidua Mill., Pinus sylvestris L. and Pinus mugo Turra. At the tested acidity degrees (pH 3.6, 3.0, 2.8, 2.6 and 2.5) of the acid rain, the rain was largely observed to have a stimulating effect on the growth of the selected vital seedlings of spruce and larch. No significant influence was observed to be exerted by acid rain on the growth of the Scotch pine and mugo pine. The effect of the rain was modified by the supply of nutrients to the roots. With a generally low concentration of all nutrients the acid rain had an adverse effect on growth. Supplemental nutrition with nitrogen intensified the stimulating effect of acid rain on the growth of the vital seedlings, but this effect was accompanied by a decrease in the proportion of vital seedlings out of the total number of seedlings. When there was a deficit of potassium in the nutrition of the seedlings, the number of vital seedlings was markedly reduced by acid rain.
