12 



their roots, and which contain micro-organisms. All other plants 

 take their nitrogen from the soil and in combination with other 

 elements. 



Nitrogen is taken up by plants largely in the form of nitrates and 

 in this form is the most active as well as the most elusive of the 

 elements of plant food. When organic nitrogenous substances decay 

 in the soil, the nitrogen which they contain is readily converted into 

 ammoniates and then into nitrites and finally into nitrates which, if 

 not taken up by the growing plant, pass away into solution and are 

 lost in the drainage waters. These facts emphasize the importance 

 of a familiarity with the behavior and functions of the various ele- 

 ments of plant food in order that they may be better controlled and 

 husbanded, and grave losses thereby avoided. 



Nitrogen in the Jonii of ammoniates and organic matter is not as 

 readily leached out of the soil as are nitrates. In many cases, fre- 

 quent and small applications of nitrogen in form of nitrates is likely, 

 therefore, to prove more economical and effective, especially in wet 

 seasons, than a large application at one time. In case of mixed 

 fertilizers, too much of the nitrogen should not be present as nitrate ; 

 usually a quarter to a third is a fair proportion. Nitrogen is a 

 powerful stimulant and when used in great excess, especially in the 

 absence of a liberal supply of available potash and phosphoric acid, 

 causes an unnatural watery growth, a large development of stem and 

 leaf, with but little fruit. 



Nitrogen is the most expensive element of plant food, costing at 

 retail from i8 to 25 cents per pound, while potash and available 

 phosphoric acid may be purchased for \Yo, to 5 ^ cents. Nitrogen 

 occurs in fertilizers in three forms, as nitrates, ammoniates and 

 organic nitrogen. 



Nitrogen in form of nitrates is supplied by nitrate of soda, the 

 average commercial product testing 95'/r nitrate of soda, equivalent to 

 about 15.5 per cent nitrogen. Nitric nitrogen may also be supplied 

 from nitrate of potash or saltpetre which, of course, furnishes valua- 

 ble potash as well as nitrogen. Two analyses of nitrate of potash 

 from samples collected in our general markets, averaged 12.47^0 

 nitrogen and 46.22'/f potash. 



Nitrogen as furnished by sulphate of ammonia, is one of the most 

 active forms of nitrogen except when used on soils deficient in lime. 



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