COMPOSITION AS AFFECTED BY TIME OF CUTTING. 



19 



of total nitrogen, a slight but irregular decrease in the percentage of 

 })roteid nitrogen in the dry matter, and a constant decrease in the 

 percentage of amid nitrogen. He holds that the amid substances 

 are converted into albumen as the kernels ripen 

 as follows : 



His figures are 



Date. 



July 13.. 

 July 18.. 

 July 24.. 

 July 29.. 

 August 3 

 August 9 



Amid 

 nitrogen. 



0.68 

 .41 

 .13 

 .22 

 .21 

 .13 



Judging from these results there can be no doubt that the per- 

 centage of nitrogen, both total and proteid, decreases as the kernel 

 develops, owing to the more rapid deposition of starch that goes 

 on during the later stages of growth. The larger part of the nitrogen 

 used by the wheat plant appears to be absorbed during the early 

 life of the plant. This is transferred in large amounts to the kernel 

 in the early stages of its development, after which nitrogen accretion 

 by the kernel is comparatively slight. The deposition of starch, 

 on the other hand, continues actively during the entire development 

 of the kernel. It would further appear that the amid nitrogen is 

 converted into proteid compounds as development proceeds. 



As showing the stages of growth of the wlfeat plant at which the 

 greatest absorption of nitrogen occurs, some experiments may be 

 quoted. 



Lawes and Gilbert " say : 



In ISSJr we took samples of a growing wheat crop at different stages of its progress, 

 commencing on June 21, and determind the dry matter, ash, and nitrogen in them. Calcu- 

 lation of the results showed that, while during little more than fiye weeks from June 21 

 there was comparatiyely little increase in the amount of nitrogen accumulated over a given 

 area, more than half the total carbon of the crop was accumulated during that period. 



Snyder's analyses* show that of the total amount of nitrogen 

 taken up by the wheat plant, 85.97 per cent is removed from the soil 

 within fifty days after coming up, 88.6 per cent b}^ time of heading 

 out, and 95.4 per cent by the time the kernels are in the milk. 



Adorjan'' finds that assimilation of plant food from the soil is not 

 proportional to the formation of dry matter in the plant, but that 

 it proceeds more rapidly in the early stages of growth. During early 

 growth nitrogen is the principal requirement. The nitrogen stored 



« On the Composition of the Ash of Wheat Grain and Wheat Straw, London, 1884. 

 f> Minnesota Experiment Station Bulletin 29, pp. 152-160. 



'"Abstract, E.xperiment Station Eecord, 14, p. 436, from Jour. Landw., 50 (1902), 

 pp. 193-230. 



