150 J* each-Growing 



the soil by the roots. Leguminous plants through the ac- 

 tion of the bacteria which inhabit their roots are able to use 

 the free nitrogen from the air, hence their value in enriching 

 soils in this plant-food element. 



It is universally recognized by the soil chemists and others 

 that all ordinary soils contain enough of all the elements 

 above enumerated except three to enable them to produce 

 maximum crops indefinitely. These exceptions are : nitrogen, 

 which very frequently is not contained in the soil in combined 

 form in adequate quantities, potassium, and phosphorus ; or, 

 expressed in the more familiar terms of the fertilizer trade, 

 nitrogen (or ammonia), potash, and phosphoric acid. Cal- 

 cium, in the form of lime, may be needed in larger quanti- 

 ties than it occurs, but for quite secondary effects rather 

 than as a direct plant-food. Substantially, then, in the 

 solution of the fertilizer problem, the peach-grower is con- 

 cerned only with these three elements, nitrogen, potassium, 

 and phosphorus. 



With this approach to the matter it might seem that a 

 chemical analysis of the tree in all its parts compared with 

 a similar analysis of the soil where the tree w^as growing 

 would show what was lacking, and the question of what 

 fertilizer to use would be easily and quickly answered. 

 But this is not the case. A chemist might make these 

 analyses, and those of the soil might show every element of 

 plant-food present in almost inexhaustible quantity, and yet 

 in actual experience it might be entirely possible that trees 

 growing on the soil analyzed would show every indication 

 of, and in fact actually be in, a depleted, starving condi- 

 tion — a case of the soil analyzing very rich in all the plant- 

 food elements, yet unfertile and unproductive. Such in- 

 stances are not only not hypothetical, but very common. 



