108 SOME OF THE CHABACTEBISTICS OF SOILS. [Dec, 



is that timber acts decidedly in the way of increasing the 

 fertility of the soil and not towards its deterioration. Some 

 tables in a recent little book on 'Agricultural Chemistry' by ]\Ir. 

 Warington, which we have by us at present will sufficiently answer 

 the purpose. From these we learn that a crop of wheat yielding 

 30 bushels to the acre, and with its straw included, requires from the 

 soil within that area 45 lb. of nitrogen, 22*7 of phosphoric acid, and 

 27"9 of potash ; and a SO-bushel-to-the-acre crop of beans, 99 lbs. of 

 nitrogen, 31'5 of phosphoric acid, and 81"1 of potash. A two-ton crop 

 of clover hay will take from each acre 102 lbs. of nitrogen, 25*1 of 

 phosphoric acid, and 87*4 of potash. Seventeen tons of turnips, 22 of 

 mangels, and 6 of potatoes, all with their respective leaves and stems, 

 will absorb 120, 147, and 67 lbs. of nitrogen, 331, 49-1, and 26-8 lbs. 

 of phosphoric acid, and 148'8, 262"o, and 76"5 lbs. of potash from 

 their several acres of soil. Unfortunately the amount of nitrogen in 

 a season's increase of Pine and Beech wood quoted is not given, 

 but Mr. Warington writes that a year's increase of Pine timber is 

 ' produced with a consumption of only 2| lbs. of potash, and 1 of phos- 

 plioric acid per acre per annum ; with Beech timber the C[uantities 

 recj^uired are rather larger. The nitrogen contained in timber is very 

 small in amount, but the actual quantity required by a forest has not 

 been accurately ascertained.' From the foregoing data, we cannot be 

 very far wrong in saying, that a single moderate crop of mangels will 

 extract from an acre of soil almost as much potash as can be required 

 by the annual growths of a forest covering a like area through the 

 long space of a hundred years ; indeed, we may say for the lifetime 

 of the trees. And during the same time an acre of forest trees will 

 only re([uire the use of twice as much phosphoric acid as will be 

 needed to serve the purposes of a single crop of the roots in question 

 on an equal plot of ground. The figures reveal also the necessity that 

 farmers are under of manuring liberally in order to insure large 

 returnr , and show the advantages that result from a judicious rotation 

 of crops, and the need there is in many cases to restrict the removal 

 of certain crops to be consumed at a distance from the farm, unless 

 some equivalent is to be returned in their stead to the soil. The 

 nitrogen and phosphoric acid, and potash contained in growing trees are 

 concentrated mostly in the leaves and twigs and tender branches — 

 the parts that are seldom removed from forest ground. The roots 

 descend far and feed on the subsoil, eating into and disintegrating the 

 hardest rocks themselves, and they are independent of the surface 

 soil for their nourishment. The leaves fall annually and decay, and 

 thus they gradually come to enrich the surface soil of plantation 

 ground ; each year they are adding to it the bulk of the valuable 

 bodies that the roots have extracted from the depths beneath. And 



