540 NATURAL FERTILITY OP SOIL. 



point till it acquires the weight of many tons, it does so by 

 gradually absorbing from the earth and air such food suitable 

 to its nature as is found there. What is derived from the air 

 may be disregarded, the constituents of the atmosphere being 

 ever renewed and inexhaustible; but inorganic matter, pre- 

 sented to our eyes by the ashes of the tree when burnt, is 

 wholly derived from the soil, which is neither ever renewing 

 nor inexhaustible. Should the tree perish where it stood and 

 there decay, the soil \5r0uld receive back all that it had given 

 up, and no exhaustion would have taken place. But if the 

 tree is felled and carried away, then the soil is robbed of all 

 the inorganic matter which entered into the composition of the 

 timber, and becomes ][)ro tanto exhausted of its nutritive powers. 

 The matter thus removed is restored by manure. And so of 

 all plants else. Such is the inevitable result of cultivation. 



Although it is unquestionable that all cultivated plants require 

 manure, on account of the exhaustibility of all soils, sooner or later, 

 yet it must he remembered that the rate of exhaustion depends upon 

 the proper nature of soil, and the treatment it receives at the hands of 

 the gardener. Sandy soils are rapidly rendered barren by cropping 

 without manure ; clayey and loamy soils much more slowly. And 

 when the latter are skUfully cultivated crop after crop of certaia kinds of 

 plants may be taken from them with no apparent loss of fertility. This 

 has been strikingly illustrated by the Rev. Mr. Smith, an accomplished 

 agriculturist residing at Lois-Weedon, a remote village on the oolitic 

 clay of Northamptonshire, where repeated crops of wheat, at the rate of 

 40 bushels an acre, have been obtained for many years successively, 

 without manure, by mere spade cultivation. This gentleman thus 

 succinctly describes his mode of tillage (the land being of course 

 thoroughly drained) : — 



" At the outset I plough the whole field early in autumn an inch 

 deeper than the staple, harrow, and roll, and harrow again — ^pulverising 

 and preparing it, in short, as for Barley. T then get in my Wheat, 

 leaving yard-wide fallow intervals between the rows. When the 

 Wheat is up I begin to dig, which is done thus : — ^At the end of the 

 interval I iif st throw out on the headland about 3 feet of soil to the 

 entire depth I intend to go the first year, and, supposing the staple to 

 be 6 inches, and the 4 inches of subsoil to be clay, this depth altogether 

 will be 10 inches. The spadesman now, with a shallow spit, casts the 

 6 inches of staple to the bottom of the trench of this yard length of 

 interval; and then, with another spit stiU shallower, throws the 4 

 inches of the subsoil lightly on the top, and so on all over the field. 



