CROPS. 45 



is in excess of that yielded by any of the cultivated crops 

 given in the table, excepting man gels. This large produce 

 is obtained by a very small consumption of soil food ; the 

 amounts of potash and phosphoric acid required are espe- 

 cially far less than in the case of any farm crop. The 

 greater part both of the ash constituents and nitrogen is 

 found in the fallen leaves ; if these are left undisturbed, 

 and allowed to manure the ground, the requirements of 

 the forest become extremely small. It appears that about 

 3000 lbs. of perfectly dry pine timber are produced with a 

 consumption of only 2J lbs. of potash, and 1 lb. of phos- 

 phoric acid per acre per annum ; with beech timber the 

 quantities required are rather larger. The nitrogen con- 

 tained in timber is very small in amount, but the actual 

 quantity required by a forest has not been accurately 

 ascertained. The growth of forest timber is plainly far 

 less exhaustive to the soil than ordinary farm culture. 

 The demand on the soil becomes, however, considerably 

 greater if the trees are cut when young, young timber and 

 small branches being far richer both in nitrogen and ash 

 constituents than the mature wood. 



Adaptation of Manures to Crops. — The true economy 

 of manure can be understood only when we are acquainted 

 with the special characters of the crops we cultivate. The 

 composition of a crop is no sufficient guide to the character 

 of the manure appropriate to it, even when we possess in 

 addition the composition of the soil on which it is to be 

 grown. It is not only the materials required to form a 

 crop, but the power of the crop to assimilate these 

 materials which must form the basis of our judgment. 

 This fact has been much overlooked by many scientific 



