CALCAREOUS MANURES-THEORY. 



29 



lands, which were originally fertile. With regard to these soils, I have 

 only to concur in the received opinion of their fitness for durable and pro- 

 fitable improvement by putrescent manures. After being exhausted by 

 cultivation, they will recover their productive power, by merely being left 

 to rest for a sufficient time, and receiving the manure made by nature, of 

 the weeds and other plants that grow and die upon the land. Even if 

 robbed of the greater part of that supply, by the grazing of animals, a still 

 longer time will serve to obtain the same resul-t. The better a soil was at 

 first, the sooner it will recover by these means, or by artificial manuring. 

 On soils of this kind, the labors of the improving farmer meet with certain 

 success and full reward ; and whenever we hear of remarkable improve- 

 ments of poor lands by putrescent manures, further inquiry will show us 

 that these poor lands had once been I'ich. 



The continued fertility of certain countries, for hundreds or even thou- 

 sands of years, docs not prove that the land could not be, or had not been, 

 exhausted by cultivation; but only that it was slow to exhaust and rapid 

 in recovering ; so that whatever repeated changes may have occurred in 

 each particular tract, the whole country taken together always retained a 

 high degree of productiveness. Still the same rule will apply to the richest 

 and the poorest soils —to wit, that each exerts strongly a force to retain as 

 much fertility as nature gave to it— and that when worn and reduced, each 

 kind may easily be restored to its original state, but cannot be raised 

 higher, with either durability or profit, l^y putrescent manures, whether ap- 

 plied by the bounty of nature, or the industry of man. 



CHAPTER IV. 



EFFECTS OF THE PRESEN'CE OF CALCAREOUS EARTH IN SOILS. 



Proposition 2. — The natural sterilUy of the soils of lower Virginia is 

 caused hy such soils being' destitute of calcareous earth, and their being in- 

 jured by the presence and effects of vegetable acid. 



The means which would appear the most likely to lead to the causes of 

 the difierent capacities of soils (or improvement is to inquire whether any 

 known ingredient or quality is always to be found belonging to improvable 

 soils, and never to the unimprovable — or which always accompanies the 

 latter, and never the former kind. If either of these results can be obtain- 

 ed, we will have good ground for supposing that we have discovered the 

 general cause of fertility, in the one case, or of barrenness, in the other ; 

 and it will follow that, if we can supply to barren soils the deficient bene- 

 ficial ingredient — or can destroy that which is injurious to them — their 

 incapacity for receiving improvement will be removed. All the common 

 ingredients of soils, as sand, clay, or gravel — and such qualities as moisture 

 or dryness— a level, or a hilly surface — however they may affect the value 

 of soils, are each sometimes found exhibited, in a remarkable degree, in 

 both the fertile and the sterile. The abundance of putrescent vegetable 

 matter might well be considered the cause of fertility, by one who judged 

 only from lands long under cultivation. But though vegetable matter in 

 sufficient quantity is essential to the existence of fertility, yet will this sub- 

 stance also be found inadequate for the cause. Vegetable matter abounds 

 in all rich land, it is admitted ; but it has also been furnished by nature, in 

 quantities exceeding all computation, to the most barren soils known. 



4 



