EGYPTIAN AG 



attention as occasion demands. Good drainage has been 

 incidentally referred to, and from the practical standpoint 

 has been fully treated in a previous chapter. 



Presuming, however, that the soil from a physical point 

 of view leaves nothing to be desired, the next condition 

 of fertility and the one with which we are here more 

 intimately concerned is the presence of sufficient plant 

 food. Not only must there be a sufficiency but it must 

 be present in such a condition that the plant is able to 

 make use of it. The soil is a most complex body, and 

 contains a great variety of substances. The bulk of it 

 merely forms the medium in which the plant grows, 

 provides mechanical support, and maintains those physical 

 conditions necessary for its existence. 



The part which is destined to feed the plant is re- 

 latively small in amount, while that part which is actually 

 capable of feeding the plant at present is still more minute. 



While a considerable number of ingredients are actually 

 necessary for the growth of the plant, yet three of them 

 assume greater importance than the others, viz : ni- 

 trogen, phosphoric acid, and potash. These acquire 

 importance from the fact that they are generally present 

 in a form in which they can be made use of by the plant 

 in smaller quantities than are the other necessary ingre- 

 dients. An essential duty of the cultivator is therefore 

 to ascertain whether his soil contains these ingredients 

 in sufficient quantities, for the partial absence of one of 

 them prevents the full development of the crop even 

 though the rest of the necessary substances are present in 

 itn ample degree. 



