10 MANUFACTURE OF FERTILIZING MATERIALS 



ground bone or ground phosphate does not readily 

 leach out of the soil. In specially prepared 

 materials, however, like dissolved bone or dis- 

 solved phosphate (acid phosphate) the phosphoric 

 acid is quite soluble and would be removed from 

 the soil by drainage water, were it not for the 

 fact that immediately after application the phos- 

 phoric acid becomes changed into another form, 

 which is not apt to leach away. 



The mineral forms of nitrogen, such as nitrate 

 of soda and sulphate of ammonia, both dissolve 

 easily in water, hence they would soon wash into 

 the subsoil and out of reach of the plants. The 

 so-called organic forms of nitrogen, like cotton- 

 seed-meal, tankage, fish-scrap, dried blood, etc., 

 are less soluble, and experience indicates that they 

 are largely retained in the soil. It is a matter of 

 observation also that there is little loss of nitro- 

 gen by drainage when the soil is covered with 

 vegetation, because the roots of the growing 

 plants absorb nitrogen very readily. 



Potash, it has been found by experience, does 

 not wash away to any appreciable extent, because 

 it forms certain combinations in the soil which are 

 not so soluble, but which at the same time are 

 readily available to the growing crops. 



In addition it may be said, in general, that loss 

 of plant food is greatest in sandy soils; the coarser 

 the sand, the greater the loss, the other con- 

 ditions being the same. Clay and humus have 

 very marked power in retaining plant food. 



