MANURES. 4" 



refer to those practices which have been pursued with 

 advantage, both in this country and in Europe. If the 

 soil be wet or marshy, it is drained and burned ; if ex 

 hausted from the repeated culture of any vegetable. 

 the crop is changed ; if still unproductive the earth i? 

 plowed and suffered to repose. If any one asks how 

 the fertility of a soil is restored by these means, it will 

 be sufficient for the object of this work to reply that. 

 in the case of draining, the amelioration is effected by 

 means of its carrying off all such superfluous moisture as 

 may be lodged in the soil, which is well known to be 

 prejudicial to plants not naturally aquatics, as well a- 

 by rendering the soil more firm and compact. In the 

 case of burning, the amelioration is effected by means 

 of the decomposition of the vegetable substances con- 

 tained in the turf, and subjected to the action of fire, 

 which disperses part also of the superfluous moisture, 

 but leaves a residue of ashes favourable to future vege- 

 tation. In the case of the rotation of crops, the fertility 

 is not so much restored as more completely developed 

 and brought into action ; because the soil, though ex- 

 hausted for one species of grain, is yet found to be 

 sufficiently fertile for another, the food necessary to 

 each being different or required in less abundance. 



In the case of the repose of the soil, the restored 

 fertility may be owing to the decay of vegetable sub- 

 stances that are not now carried off in the annual crop, 

 but left to augment the proportion of vegetable mould ; 

 or to the accumulation of fertilizing particles conveyed 

 to the soil by rains ; or to the continued abstraction of 

 oxygen from the atmosphere. 



In the case of fallows, it is owing undoubtedly to the 

 action of the atmospheric air upon the soil, whether in 



