Methods of Use of Fertilizers 199 



market value, and carry away but minimum amounts of 

 the fertilizing constituents. This distinctive character of 

 crops, while not an absolute guide as to the profits that may 

 be obtained from the use of fertilizers, since the cost of 

 production varies widely for each class, is instructive 

 in showing that those of a low commercial value are more 

 exhaustive than the other class, or those of a high market 

 value, and is certainly suggestive, pointing out the neces- 

 sity for judgment in the application of fertilizers that shall 

 be made in the case of crops of the different groups. 



The kind of farming, whether "extensive or intensive." 



Another very important consideration, and one which 

 exercises an influence, is whether the farming engaged in 

 is "extensive" in its character, or "intensive"; whether 

 the purpose or idea is simply to supplement the stores of 

 plant-food in the soil, or whether the object is to insure an 

 abundance of all forms of constituents under all reasonable 

 conditions, in order that a maximum production may be 

 secured. 



PLANTS VARY IN THEIR POWER OF ACQUIRING FOOD 



In the next place, the character or feeding capacity of 

 the plant and its season of growth should be considered, 

 that systematic methods may be adopted, and thus not 

 only that waste of fertilizing materials may be avoided, 

 but that the applications may be made at such times and 

 in such amounts as will, other things being equal, promote 

 the greatest increase per unit of applied food. 



While each plant possesses individual characteristics 

 which distinguish it from all others, for our purpose they 

 may again be classified into general groups which possess 



