64 SOILS 



be here to-day? When we find it so difficult to hold fast 

 to the little that has been given us, do you think we were 

 able to care for plant food in all its entirety, had it been 

 i^'iven into our keeping? If man knows not how to use 

 Mis one talent, shall he be given two? 



Let me assure you of this : it is better that things are 

 as they are, for had they been different, had all the plant 

 food been just ready to use from the very beginning of 

 time, then long before this the sea had gathered it up: 

 to have it and to hold it, until its bottoms had been filled 

 and its banks had been broken ; until new sea beds had 

 been formed, until the old reservoirs had been robbed 

 of their holdings by wind and air plant food should be 

 urgently required else all life would be lost ; else the 

 entire world would be ruined and destroyed. 



How plant food is held. We gather from this that 

 some plant food is available for use, and some of it is not. 

 We may say then that three forms of plant food exist in 

 the soil. 



These three forms are : 



1. Available plant food. 



2. Not-immediately-available plant food. 



3. Tightly-secured plant food. 



Let us now examine these forms individually. 



Available plant food. You have, doubtless, 

 seen nitrate of soda or wood ashes. Both of 

 these materials are used to make plants grow ; 

 for this purpose they are purchased. They are 

 plant foods. The nitrate of soda or wood ashes 

 are used because the nitrogen or the potassium 

 contained therein is in each case available plant 

 food ; that is, growing plants will be able to use 



A ROOT HAIR ^^g material just as soon as it gets 

 WITH SOIL . . . 



ATTACHED mixed with the soil grains and wetted with 



