9 SOILS AND FERTILIZERS 



During the time of seed formation more nitrogen was 

 added, but with no beneficial result. All of the es- 

 sential 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 want of nitro- 

 gen, 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 

 necessary 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 85 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 75 

 per cent, of its nitrogen during the first fifty days of 

 growth. 38 



Nitrogen is demanded by all crops. It forms the 

 chief building material for the proteids of 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 

 of chlorophyl, *the green coloring-matter of plants, 

 hence when there is a lack of nitrogen only a limited 

 amount of chlorophyl can be produced. Plants with 



