XXIII. FERTILIZERS 



EACH crop secures the necessary elements for its growth from the 

 air and the soil. Each year certain minerals are removed from the 

 soil, and it is evident that in course of time the supply of necessary 

 minerals will become exhausted if not replenished by some means. 

 This takes place when we grow year after year some crop that 

 draws and requires a large supply of a certain mineral element 

 from the soil. To remedy the evil the farmer must either grow a 

 new crop that draws on a different element of the soil, or he must 

 strengthen the soil by applying to it some substance that will 

 supply the missing element. 



Fertilizers Defined. Anything that we may apply to a soil 

 to make it more fertile or productive is a fertilizer. Fertilizers 

 may be divided into two classes: (1) natural fertilizers, and 

 (2) commercial fertilizers. 



Natural Fertilizers. In this class we may include those which 

 occur in nature and may be applied with or without special treat- 

 ment to make them useful as fertilizers, and those which are by- 

 products of manufacture or farm operations. They are lime, marl, 

 gypsum, gas lime, salt, wood ashes, leather meal, felt waste, hair 

 waste, swamp muck, peat, leaves, straw, and barnyard or stable 

 manure." 



Lime and Gas Lime. Lime (calcium oxide) is a compound of 

 calcium and oxygen. It is produced by burning common limestone. 

 Lime is an essential food of the plant, and it exercises a beneficial 

 effect on the soil by overcoming and neutralizing any acids present. 

 In many parts of Alaska so much acid is present in the soils that 

 crops cannot be grown with success until enough lime has been 

 added to counteract the sourness. The judicious use of lime 

 liberates unavailable plant food, eradicates diseases, and improves 

 the texture of the soil. Gas lime contains a great deal of sulphur 

 in the form of sulphides which are somewhat injurious to plant 

 life and should be applied to the soil in sparing quantities long 

 before the planting of the crop. 



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