IDEAL FERTILIZERS 7 



ture, especially if lime is added to induce "flocculation," 

 the gathering together of fine particles to make a soil 

 grain. This trouble is found particularly among clay 

 soils. Our new land is inclined to be too coarse and raw. 

 No treatment can bring it into right texture immedi- 

 ately; it takes time and cultivation to accomplish this. 



Air Air in the soil is necessary for the respiration of 

 the roots and the development of our friendly bacteria. 

 It is also important in promoting chemical changes. 

 Many of these are forms of oxidation and through them 

 much plant food becomes available. This is especially 

 noticeable in the formation of nitrates as taken up under 

 "Bacteria." It will also be seen that the air supply 

 determines through its influence on bacteria, whether 

 organic matter becomes plant food or plant poison. Too 

 much air allows a drying-out of the soil, thereby de- 

 creasing the water supply of the plant. 



Water Capillary water is that held in films around 

 the soil grains and is the ideal form of soil moisture. 

 The smaller the soil grains the more surface they pre- 

 sent, therefore, to a certain extent, the more water held 

 by capillarity; and the more water in contact with the 

 soil, the greater amount of plant food brought into avail- 

 ability. Free water, or ground water, is that which 

 would run off if given a chance. It fills the spaces be- 

 tween the soil grains, thereby shutting out the air and 

 bringing on the many troubles caused by such conditions. 

 Such water should not be allowed within three feet of 

 the surface. 



