iron, lime, magnesia, silicon, aluminum and soda are in the soil. Water 

 is a compound composed of oxygen and hydrogen, and is utilized by the 

 plant through its roots. Humus, another compound, is absolutely 

 indispensable. 



The availability and usefulness of all of the component parts of fer- 

 tility depend upon the judgment and activity of the farmer. The sup- 

 ply may be abundant, but if the operations pertaining to production are 

 mismanaged, the crop will be disappointing. 



Carbon 



Carbon in the form of carbon dioxide is absorbed from the atmosphere 

 through pores or stomata in the leaf and converted into plant substances 

 just in proportion to the size and health of the plant above ground. 

 Good seed in a mellow soil, well watered and aerated, causes a strong, 

 rapid growth, insuring an abundance of carbon. 



Nitrogen 



Three-fourths of the atmosphere is nitrogen. One medium through 

 which it can be secured and placed in the soil is the legume. A crop of 

 one hundred bushels, including the stalks, requires about one hundred 

 forty-eight pounds of nitrogen. Commercial nitrogen is worth twenty 

 cents per pound. The value of nitrogen alone in the crop of one hun- 

 dred bushels is, therefore, $29.60. This can be furnished free of cost if 

 legumes are grown on the ground the previous year. By referring to 

 the chapter on Rotation, it will be seen that legumes not only furnish 

 nitrogen, but make available other elements and improve the soil in 

 many ways. 



Potash 



Potash is found in disintegrated particles of rock which form the body 

 of the soil. Most soil contains enough to last until the end of time. In 

 clay soils it is very abundant. Peaty soils are apt to be deficient. 

 Potash can be supplied by adding barnyard manure, wood ashes, kainite 

 or other forms of potassium. Quite often it will be found that a soil is 

 rich in potash, but that the element is dormant or unavailable. This 

 condition can be remedied by applying lime. Weak, slender, long- 

 jointed stalks indicate a lack of potash. 



Phosphorus 



Phosphorus, like potash, is found in disintegrated particles of rock. 

 Phosphorus is of no value as a plant food until it is made soluble; or, in 

 other words, transformed into phosphoric acid. This is accomplished 

 by applying barnyard manure to the land. When fermentation takes 

 place, carbonic acid is formed, which, in conjunction with the other 

 acids, acts upon the phosphorus, rendering a small per cent soluble. 

 Where manure cannot be obtained, green crops should be plowed under. 



