A STUDY OF FACTORS AFFECTING THE NITROGEN 
CONTENT OF WHEAT AND OF THE CHANGES THAT 
OCCUR DURING THE DEVELOPMENT OF WHEAT' 
By Georgb a. Olson* 
Chemistt Washington Agricultural Experiment Station 
INTRODUCTION 
The subject matter of this paper pertains to a study of the nitrogen 
content of wheat produced under various experimental conditions and 
a study of changes that occur during the development of wheat. The 
investigation had its inception in studies of nitrogen content of wheat 
by Thatcher (jj, 32, 33)} 
In the States of California, parts of Idaho, Montana, Oregon, Utah, 
and Washington, wheat, irrespective of variety, generally develops large, 
plump kernels of comparatively soft texture. The nitrogen or gluten 
content of these soft wheats is variable, with localized districts apparently 
more favorable to the production of wheat with high percentages of 
nitrogen or gluten than is observed in others. Farther east, in the States 
of North Dakota, South Dakota, Nebraska, Kansas, Minnesota, Missouri, 
and Iowa the wheat kernels, generally, are of smaller size. These 
smaller-sized kernels, however, may be plump yet the texture of the 
grain may be comparatively harder. The percentage of nitrogen or 
gluten in this harder type of wheat varies but, generally speaking, 
is comparatively higher than in the softer wheats. 
The influence of exchange of seed, breeding new varieties, selections 
for nitrogen content, soil types, soil treatment, fertilizers, water, and 
temperature on the percentage of nitrogen in wheat have been studied 
by various investigators. Frofn the results of investigation, it is held 
that the variation in composition of wheat is due, chiefly, to variation 
in environmental conditions, such as rain, sunshine, humidity of the 
atmosphere, methods of harvesting, methods of cultivations, and amount 
of manure. The effect of continuous cropping, rotation, the method 
and time of sowing seed, including the quantity and quality of the 
seed sown, have also been studied. With the exception of irrigation, 
the first three of these conditions are wholly uncontrollable; the remainder 
of them can be regulated, and it is to these that the investigational work 
has been and should be directed to determine whether or not the nitrogen 
content of wheat can be increased. 
HISTORICAL REVIEW 
EFFECT OF CLIMATE ON NITROGEN CONTENT OF WHEAT 
Over 60 years ago, Lawes and Gilbert (7) concluded from their experi¬ 
ments that long periods of growth produced plump kernels of low nitrogen 
content. Later these men {8) stated that— 
a season favorable for long and continuous growth after heading, produced well devel¬ 
oped kernels and larger yields; the mature grain developed under the most favorable 
conditions contained a high amount of starch and a low amount of potash, phosphoric 
acid, and nitrogen. 
* Accepted for publication Oct. 17, 1921. 
* The author desires to thank Alexander Carlyle, L- F. Seneco, and Sam Bockman for their assistance in 
looking after the field work. 
* Reference is made by number (italic) to “Literature used," p. 9Si”9S3. 
Journal of Agricultural Research, 
Washington, D. C. 
aez 
43325—23 - 5 
939 
Vol. XXIV, No. tt 
June 16, 1923 
Key No. Wash,-3 
