NITROGEN AS A PLANT FOOD IO3 



thirty-six hours the plant showed signs of renewed 

 life, the leaves assumed a deeper green, a new growth 

 was begun, and finally four seeds were produced. 

 During the time of seed formation more nitrogen was 

 added, but with no beneficial result. All of the 

 essential elements for plant growth were liberally pro- 

 vided, except nitrogen which was very sparingly sup- 

 plied at first, until near the period of seed formation, 

 when it was more liberally supplied. 



When plants have reached a certain period in their 

 development, and have been starved for the want of 

 nitrogen, the later application of this element does not 

 produce normal growth, as the energies of the plant 

 have been used up in searching for food. Nitrogen, as 

 well as potash, lime, and phosphoric acid, are all neces- 

 sary while plants are in their first stages of growth. 



In the case of wheat, nitrogen is assimilated more 

 rapidly than are any of the mineral elements. Before 

 the plant heads out, over eighty-five per cent, of the 

 total nitrogen required has been taken from the soil. 36 

 Corn also takes up all of its nitrogen from four to five 

 weeks before the crop matures. Flax takes up 

 seventy-five per cent, of its nitrogen during the first 

 fifty days of growth. 37 

 /"* Nitrogen is demanded by all crops. It forms the 

 chief building material for the proteids of all plants. 

 In the absence of a sufficient amount of nitrogen, the 

 rich green color is not developed ; the foliage is of a 

 yellowish tinge. Nitrogen is one of the constituents 



