196 



NITROGEN, PHOSPHORUS AND POTASSIUM 



COMMERCIAL FERTILIZERS 



Commercial fertilizers are manufactured preparations used to 

 ad'd plant-food elements to the soil, particularly nitrogen, phos- 

 phorus and potassium. These elements in fertilizers are commonly 

 expressed as ''ammonia (NH3),'' ''phosphoric acid (P2O5),'' and 

 "potash (K2O)," respectively. The ammonia is commonly re- 

 ferred to as nitrogen (N). To avoid any misconceptions, the 

 names of the elements are retained in this discussion. 



Some substances, as common salt, for example, are called soil 

 stimulants, or indirect fertilizers, because they do not contain any 

 nitrogen, phosphorus or potassium, but cause changes in the soil 

 liberating the plant-food elements already there. 



Four Classes of Commercial Fertilizers. — Commercial fertil- 

 izers may be grouped into four classes, viz.: (a) Nitrogen 

 fertilizers; (&) phosphorus or phosphate fertilizers; (c) potassium 

 or potash fertilizers, and (d) mixed fertihzers. 



Nitrogen Fertilizers. — The common nitrogen fertilizers are: 



Common names 



Per cent 

 mtrogen 



Availability 



(a) Nitrate of soda, or sodium nitrate 

 (5) Ammomum sulfate, or sulfate of 

 ammoma 



(c) Dried blood, or blood meal 



(d) Cottonseed meal 



15 



20 

 6-15 

 4-8 



Very readily available. 



Keadily available 

 Becomes qmckly ava.ilable 

 Nearly equal to dried blood 



Other mtrogen fertilizers are Dried meat scraps tankage dried ground fish scrap, 

 hoof meal, guanos, wool waste, peat, calcium cyanamid, calcium nitiate, and others 



Nitrate of Soda. — The best known and most widely used 

 nitrogen fertilizer is nitrate of soda. This is a salt obtained from 

 natural deposits found particularly in northern Chili. The origin 

 of this large deposit is not definitely known. 



Nitrate of soda can be utilized directly by plants without first 

 undergoing decomposition changes. Because of its solubility and 

 the ease with which it is leached from the soil, the amount applied 

 to the acre at any one time is not very large. The usual application 

 is from 100 to 400 pounds applied in frequent small amounts during 

 the early growing period. It is often used in small quantities to 

 force plant growth, as on tobacco beds. Market gardeners and 

 truck growers use this fertilizer more than do general farmers, and 

 it is used more extensively in the eastern states than in the western. 



Ammonium Sulfate. — Sulfate of ammonia is a salt made as 



