ACTION ON MINERALS 89 



it into solution in the form of calcium bicarbonate, 

 which is removed in the drainage water. Thus ultimately 

 all of the limestone that was formed in the sea is returned 

 to it, largely by virtue of the indirect action of soil organ- 

 isms. It is estimated that lime is being removed from our 

 soils at the rate of from 400 to 1,000 pounds an acre each 

 year. The increased amount of decomposition of organic 

 matter due to cultivation of the soil hastens the removal 

 of the limestone therefrom. Ultimately the lime is removed 

 to such an extent that the soils tend to become acid, and 

 limestone must be added. This again favors decomposition 

 of the organic matter, and the removal of the lime is has- 

 tened. 



It is improbable that the organic acids, hasten to a great 

 extent the removal of calcium carbonate from the soil. 

 It is true that they will act on this mineral: salts of the 

 respective acids which are soluble in water will be formed. 

 The acid radicle of these salts will be decomposed and 

 carbon-dioxide will he produced, which will combine with 

 the calcium to form calcium carbonate again. The cal- 

 cium nitrate formed in the soil may be leached therefrom. 

 In the ocean this salt is decomposed by certain bacteria, 

 forming therefrom gaseous nitrogen and calcium carbonate. 



It is probably true that the calcium contained in organic 

 matter appears as calcium carbonate at the end of the de- 

 composition process. The amount thus formed is but a 

 small fraction of that removed from the soil. 



Lime is added to the soil in the form of ground limestone 

 (carbonate of calcium, marl) or burned lime (calcium 

 oxide). It is essential that lime be in as fine a state of 

 division as possible, so that it can be mixed thoroughly 

 with the soil and be brought in intimate contact with each 

 soil grain. 



Phosphorus. Phosphorus is another element that is 



