90 ORGANIC MATTER NECESSARY TO VEGETABLE GROWTH. 



and in every soil, cause good crops to grow, must, in addition 

 to mineral or saline, contain also some animal or vegetable sub- 

 stances, or, in their stead, some ingredients of organic origin, 

 which chemistry may point out as likely to supply the place, by 

 performing the natural functions of animal and vegetable 

 matter. 



This general result is by no means inconsistent with the good 

 effects which are, I believe, truly enough stated to have, in 

 numerous cases, followed from the unassisted application of 

 purely mineral as well as of purely organic substances or mix- 

 tures, to certain soils and crops. But the circumstance of such 

 results being possible, only shows more clearly the money value 

 to the practical man of that kind of knowledge which is likely 

 to enable him to distinguish where and when they can respec- 

 tively be expected to succeed, and in what circumstances the 

 chance of failure and of consequent loss predominates. 



Some of these circumstances, as regards purely mineral 

 manures, are stated, or may be inferred from what is contained 

 in the following section. 



5. Circumstances in which saline, or mineral applications are 

 likely to produce the most sensible effects. 



1. Saline substances act most immediately and most effi- 

 ciently when they are in an exceedingly minute state of division, 

 and when the land and crops to which they are applied are 

 already moist, or when rain falls soon after the application. 



2. Generally they produce most effect upon soils which contain 

 the least of the several ingredients of which the saline substances 

 themselves may consist. 



This general rule, however, involves and may be subdivided 

 into several special rules or cases. Thus, 



a It is the result of observation that saline applications of 

 certain kinds, whether single or mixed, produce the most marked 

 effects on comparatively poor soils. Those which are naturally 

 rich, in the ordinary sense of the term, are less likely to exhibit 

 striking differences when a top-dressing of a saline substance is 

 applied to them, because the quantity of the substance laid on, 

 compared with the weight of the same substance already present 



