12 FOREST POLICY. 



(XIII.) SOIL REQUIREMENTS IN FORESTRY. 



Proper forestry does not require fertilizing in the long run. Trees 

 take from the soil smaller percentages of mineral matter than do field 

 crops. (See Table No. 6 from Schlich.) 



In addition, trees take mineral food from the lower as well as 

 from the upper strata of soil. Ebermeyer finds that an average forest 

 crop (i cord of wood or 200 feet b. m. with leaves and branches per 

 acre per annum) takes 54 per cent of the mineral substance required 

 for an ordinary field crop. Of this 54 per cent, however, 46 per cent. 

 (of the whole) is restored to the ground when the leaves fall. Only 

 8 per cent, is actually imbedded in the wood fibre. After other author- 

 ities, the disintegration of the rock keeps pace with the exhaustion 

 of the soil in the case of trees. 



TABLE No. 6. 



Table showing pounds of mineral matter required, per acre and 

 year, for crops in field and forest: 



Substance: KjG CjO MgO P^Os S O2 SiO^ 



Field Crop: 78 43 17 28 11 37 



Forest Crop : 4 9 2 1.4 0.4 1.6 



