Chapter Twenty-Three 

 NITROGEN 



Nitrogen is so important in the growth of plants that a 

 complete chapter is given to its discussion. It is a large im- 

 portant part of the living material of the plant protoplasm 

 and of the storage protein. As shown by the photographs 

 (Plates XI and XII) its complete absence from the soil solu- 

 tion retards growth as much as though the plant were de- 

 prived of all salts; in fact, it might be called the limiting 

 element. 



Most soils are deficient in nitrogen and, therefore, its 

 application brings a quick response in growth and improved 

 color of the leaves. These pleasing results tempt the gar- 

 dener to overstimulate with nitrogen and so to produce a 

 plant with larger cells, longer internodes, larger leaves and a 

 smaller root system (Plate XIII). Nitrogen should be 

 applied most heavily in the early stages of germination of a 

 plant to encourage rapid growth, and in decreasing amounts 

 later in the season in order that as it ages the plant will 

 develop sturdy structure and will store larger amounts of 

 food material. Plants so treated are less likely to winter kill 

 than others and are able to use the stored food for rapid 

 growth the next season. 



The carbon to nitrogen ratio was discussed at some length 

 in Chapter 14. The idea of ratio should be kept in mind in 

 dealing with any phase of the nitrogen problem. The plant 

 can be kept considerably off a balanced carbon and nitrogen 

 ratio to produce a desired type of growth. All the methods 

 for controlling the ratio may be used, but certainly it is influ- 

 enced most by the pruning, the amount of sunlight, the soil 

 moisture, and the applications of nitrogen. 



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