FERTILIZERS 105 



different crops be used in the test, since the lacking element 

 may not be the same for each. In any soil the need for cal- 

 cium may be easily discovered by treating part of a field with 

 lime and comparing the treated area with the part not treated. 

 The lime should be applied at the rate of twenty bushels or 

 more to the acre. When red clover and alfalfa grow well on a 

 given soil, this is a good indication that it contains sufficient 

 calcium. A growth of mosses indicates a lack of this element. 

 Sources of the needed elements. It is only in exceptional 

 cases that the cultivator concerns himself about any element 

 in the soil except potash, nitrogen, and phosphorus. These 

 three are seldom abundant, and the farmer always adds fer- 

 tilizers containing them when they can be cheaply obtained. 

 Stable manure is called a " complete " fertilizer because it con- 

 tains portions of all three. Before the advent of the white 

 man the Indian had discovered the value of fish as a ferti- 

 lizer. Near the coast it was the custom to place a fish in each 

 hill of corn. In many places fish is still used for fertilizer. 

 Several other available sources of the necessary elements exist. 

 Nitrogen is found in guano, fish guano, dried blood, slaughter- 

 house waste, bone meal, linseed and cottonseed meal, ammo- 

 nium sulphate (a product of gas works), potassium nitrate, and 

 sodium nitrate, or Chile saltpeter. The sodium nitrate is the 

 most soluble. Potash is found in wood ashes, muriate of pot- 

 ash, sulphate of potash, and kainit. Phosphorus occurs in bones 

 and bone meal, phosphate rock, and Thomas slag, which is a 

 by-product in the manufacture of steel. When necessary to 

 apply calcium it may be in the form of ground limestone, quick- 

 lime, marl, gypsum, shells, and bones. In applying fertilizers it 

 is well to remember that some are more soluble than others and, 

 applied in too great quantity, may easily make the soil water 

 so dense as to kill or greatly retard the plants it was designed 

 to help. Other fertilizers, becoming available more slowly, may 

 not show their effects upon the crops until the second season. 



