raise a plant, but it is expensive, requires close watch 

 ing, and is not practical. The nitrogen from organic 

 fertilizers is yielded to the plant gradually, with 

 greater certainty, and is more lasting. 



Organic manures, whether of blood and bone, or 

 stable manure, or green cover crops, not only furnish 

 nitrogen to plant life, but their decay generates 

 several well known acids, notably carbonic, which 

 combine with soil moisture and dissolve other forms 

 of plant food. Without these acids, phosphorous, 

 potash, and other necessary elements would not be 

 so available to the plant. Direct root and water 

 action would then have to do the work alone, and 

 the plant would not thrive so well. Humus influ- 

 ences the availability of the phosphoric acid and 

 potash and converts them into forms more readily 

 utilized by the plant. 



Organic fertilizers lighten soils. Their decay 

 leaves the soil open and porous. More oxygen is 

 thus admitted, which gives more life to the micro- 

 organisms which, after all, are the cause of all 

 fertility. Better cultivation is possible in such soils. 

 Light, porous soils are more retentive of moisture. 

 Thus, organic matter literally builds up a soil. It 

 increases its depth. A " worn-out " soil is simply a 

 soil devoid of humus. It is lifeless. Liberal applica- 

 tions of organic matter restore it and change it from 

 a tax to an income. 



43 



