1 72 THE FIRST BOOK OF FARMING 



IMPORTANCE OF FARM MANURES 



Of these two classes of manures the farmer 

 should rely chiefly on the farm manures letting 

 the commercial fertilizers take a secondary place 

 because : 



Farm manures are complete manures ; that is they 

 contain all the necessary elements of plant food. 



Farm manures add to the soil large amounts of 

 organic matter or humus. 



The decay of organic matter produces carbonic 

 acid which hastens the decay of mineral matter in 

 the soil and so increases the amount of available 

 plant food. 



The organic matter changes the texture of the 

 soil. 



It makes sandy soils more compact and therefore 

 more powerful to hold water and plant food. 



It makes heavy clay soils more open and porous, 

 giving them greater power to absorb moisture and 

 plant food. This admits also of better circulation 

 of the air in the soil, and prevents baking in dry 

 weather. 



Farm manures influence all of the conditions 

 necessary for root growth while the commercial 

 fertilizers influence mainly the plant food condi- 

 tions. 



The farm manures are good for all soils and 

 crops. 



They are lasting in their effects on the soil. 



