Commercial, Fertilizers 1693 



the soil, a short rotation and tlie growing of some leguminous 

 plants. 



At the present rate of usage, which will probably be continued 

 for many years, the world's supply of chemicals from which nearly 

 all of the commercial fertilizers are manufactured, cannot always 

 last. Let us hope that the supply will not fail before farmers have 

 learned the true method of maintaining the fertility of the land. 



Commercial fertilizers, at present, if intelligently used will gen- 

 erally bring a good profit. 



Of the ten or more elements required for plant growth, compar- 

 atively only a few years ago but three of them (nitrogen, phos- 

 phoric acid and potash) were considered deficient in available form 

 to grow maximum crops. Under present conditions the use of 

 lime has proven that in many soils it is the controlling factor for 

 plant growth. 



It would be difficult to give the exact function of the different 

 elements of plant food, each is so interwoven with the other, but 

 generally considered they are as follows : 



Nitrogen. Promotes growth and green leafage. Where only 

 stalks and leaves are desired, as in the case of lettuce, celery, or 

 grass that is not to bear seed, even a limited excess of available ni- 

 trogen will do no harm, unless lodging of the plant follows. An 

 excess of nitrogen in comparison with the phosphoric acid and pot- 

 ash, retards and lessens flower and fruitage. 



Phosplioric Acid. Promotes quick germination of seeds, en- 

 larges root growth, hastens development, and increases the amount 

 and weight of seeds. In other words, it has a decidedly beneficial 

 effect upon the reproductive part of the plant. 



Potash. The action and effect of potash on the plant is not so 

 well understood as is that of some other elements, but its favorable 

 influence on the formation of starch and other carbohydrates, and 

 its effect in giving strength to straw and stalk, are well recognized. 



Lime. Generally considered an amendment, is, in part, a plant 

 food. It acts upon the soil and makes available other mineral ele- 

 ments ; it corrects acidity where there is free acid, and it promotes 

 bacterial action which hastens the decay of organic matter. It 

 may also have a beneficial effect upon the physical condition of 

 some soils, especially claj. 



