186 THE EFFECTS OF 



about Albany, 25 to 30 per cent, of carbonate of lime, 

 applied, agreeably to the foregoing directions, to an acre 

 of land like Nos. 14 and 15 of the above table, of 

 more ultimate benefit than an equal number of loads of 

 barn-yard manure. 



The majority of soils do not contain more than five 

 per cent, of humus ; and, as we have observed, many 

 contain little or no carbonate of lime. Without the first, 

 no admixture of earths can be productive ; and without the 

 latter, wheat, and probably some other farm-crops, can- 

 not be grow^n to advantage. Yet where there is a due 

 admixture of sand and clay, two per cent, of carbonate 

 of lime, and an equal proportion of humus, will render 

 the soil productive, for a season, or until the lime and the 

 dung are too far exhausted by the growing crops. Sandy 

 soils are much more easily wrought than clay soils ; and 

 if they are tolerably well dunged and managed, or if green 

 crops are made frequently to alternate, they make a good 

 return to the husbandman. Under constant tillage they 

 are soon exhausted ; and it is but seldom they are found 

 to yield a succession of grass crops. Alternate husbandry 

 should therefore, at all events, be resorted to upon soils 

 of this description. 



CHAPTER XIX. 



EFFECTS OF CROPPING AND MANURING. 



The reader will find a further illustration of the bene- 

 fits of manuring, of alternating crops, and of abolishing 

 naked fallows, in the facts and suggestions which we are 

 about to present him. 



We have heretofore endeavored to make it plain, that 

 living and dead plants contain the same elementary mat- 

 ters, — that dead plants afford the proper aliment for liv- 

 ing plants, — and that, consequently, the fertility of a soil 

 will be increased or diminished, in proportion to the quan- 

 tity of dung or organic matter which is returned to it, 



