ILLINOIS STATE DAIRYMEN'S ASSOCIATION 275 



Nitrogen may be present in fertilizers in three different 

 forms, as nitrate, aimnonia, or organic compounds. The first 

 two forms of nitrogen are of immediate value to crops, since 

 they are easily soluble' and may be readily assimilated by plants. 

 Organic nitrogen is the form of nitrogen found in fertilizers 

 of vegetable or animal origin. Some of these, like leather oi 

 woolen scraps, hoofs, horn shavings, etc., possess very little 

 value as fertilizers, being insoluble and but slowly decomposed 

 in the soil. The fertilizer laws of many states do not recognize 

 nitrogen contained in materials of this kind as of any value. 

 Available nitrogen means nitrogen supplied in nitrates, ammonia 

 salts, or organic compounds of easily decomposable character, 

 like dried blood, tankage, cotton seed meal, etc. The determina- 

 tions of soluble nitrogen in the licensed mixed fertilizers sampled 

 and analyzed by us during the past season, will give valuable in- 

 formation as to the amounts of directly available nitrogen pres- 

 ent in the different licensed brands of fertilizers. 



The main nitrogenous fertilizers used in this state are nitrate 

 of soda, tankage, and dried blood. The first mentioned fertili- 

 zer is mostly used by market gardeners and florists, and is of 

 great value in stimulating the growth of plants by furnishing 

 immediately available plant food; the other materials mention- 

 ed are also valuable fertilizers, but are slower in their action; 

 they make up the bulk of the nitrogenous components of nearly 

 all the commercial fertilizers on our market. Nitrogen is the 

 most costly ingredient of artificial fertilizers. Certain kinds 

 of plants, like the clovers, alfalfa, vetches and other species of 

 the legume family, through the agency of microscopic organ- 

 isms, are able to transform the free nitrogen of the air to or- 

 ganic nitrogenous compounds, which may be used for the nutri- 

 tion of farm animals and thus indirectly, and indeed directly, 

 contribute to the supply of nitrogenous plant food in the soil. 

 The farmer adopting a system of crop rotation in which clover 

 or other crops of the legume family are included, may often 

 avoid a cash outlay for nitrogenous fertilizers, and need only 

 see to it that the supply of potash and phosphoric acid in his 

 soil is not unduly reduced through continuous cropping. 



