The experience deals with the germination and growth of Scotch Pine (Pinus sylvestris) and Norway Spruce (Picea excelsa) cultivated on humus of the Mor type, which were treated by different chemical means. Seedlings were started during fall 1958, using seedbeds of 0,5 m 2 of surface and 0,30 m thick. They were transplanted on the spot with a spacing of 500 to the m2 during fall 1959. Finally all of them were unrooted, measured, weighet, and carefully examined in November 1959. The four treatments of the experience, repeated twice for each species are the following: T : control, Mor, pH 3,8, C/N 36.N: same ; kind of humus, neutralized by injection of gaseousNH3 .E : sanie kind of humus improved by the following fertilizer: 500 g of « scorias » and 250 g of ammonium sulfate to every 100 kg of humus. E-Ca : same treatment, the humus being here neutralized by addition,of 1,1 kg of CO 3Ca to every 100 kg of moist humus. The evolution of the different humus received great consideration ; seedling nutrition was controlled by leaf analysis, carried out subsequently in April and November 1959. Finally, a completeanalysis, of the mean seedling from every treatment was also carriedout.The main findings may be summarized as follow:1° The simple mechanical treatment of the raw humus resulted in a favourable evolution of the different ones, with increasing pH and exchangeable bases content. This substratum was profitable to Pine, while Spruce showed a light nitrogen deficiency the first year, (which was corrected the following year after transplanting). 2° The neutralization by use of gaseous ammonia had negative effects : severe damping-off and unbalanced seedling nutrition. The humus treated the first year encountered losses in humic acids andbases due to leaching. Nevertheless, at the end of the second year, the pH value came back to 4,2 and supplies in exchangeable ammonia were out. 3° The treatment iusimi fertilmcrs was so far the most successful with a final pH (5) which seemed to be the best. Spruce, more than Pine, made better use of these fertilizers, namely- phosphorous. The improvement N with addition of anunoniacal nitrogen, although quite useful the first year, had but a mere brief influence: the seedlingsbeing much less supplied the following year by this element thanthose from the control. 4° The ucntralifatioil by calcareous mixture (with fertilizers) was more harmful than useful: losses in gaseous nitrogen or by the biological fixation of ammonium seemed to be immediate and intensive, (light nitrogen deficiency in Spruce the first year). Plus, an excessive absorption of calcium seemed also harmful to the absorption of magnesium : at a pH of 7,1 a marked magnesium deficiency caused yellowing of the leaves and high growth reduction.