Manures and fertilizers are applied to the soil for their beneficial effects on these necessary conditions for root growth and therefore to assist in maintaining soil fertility.
CLASSIFICATION OF MANURES AND FERTILIZERS
Manures may be classified as follows:
| Farm manures. | { Barn or stable manures, |
| { Green-crop manures, | |
| { Composts. | |
| Commercial fertilizers or artificial manures. | { Materials furnishing nitrogen, |
| { Materials furnishing phosphoric acid, | |
| { Materials furnishing potash, | |
| { Materials furnishing lime. | |
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.