70 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
rate of supply of nitrogen to the growing plants determines the protein 
content of grain, nevertheless many factors may affect the rate of 
supply of nitrogen to the plants. Thus the methods of culture to be 
employed which will effect the desired end will vary with, and depend 
on, conditions that prevail in wheat-growing areas. Undoubtedly 
the quality of wheat could be markedly improved in many places if 
cultural methods were used that would provide the production of 
sufficient nitrogen during a portion of the latter part of the growth 
period of the plants. Application of nitrate to partially matured 
plants in fields where the grain is usually low in protein is, in most 
cases, impractical. Furthermore, success of this method would be 
conditioned by ample rainfall to make the salt available, and this is 
usually precluded by the character of the season. 
Thus it appears that the most promising method would be one that 
would utilize the character of soil and particularly that fraction which 
is organic matter to act both as a storehouse for and a regulator of the 
supply of available nitrogen. Certain methods of soil management 
and crop rotation could be instituted that would undoubtedly affect 
the rate of supply of nitrogen for any particular year in which wheat 
is to be grown on any given piece of land. Manures which nitrify 
relatively slowly presumably could be used to advantage in the pro¬ 
duction of high-protein wheat. 
But aside from the improvement of the quality of wheat directly 
through nutrition, methods of selection and breeding for high-protein 
varieties undoubtedly must be continually employed. JEToweyer, 
because of the failure to recognize, first, the underlying physiological 
cause for differences and variation in the protein content of wheat, 
and second, the relation of genetic characters to the physiological 
cause, the method for improvement of wheat by selection has been 
rendered quite tedious. It has kept workers in the dark as to the 
essential factors that determine the desired results. It is, therefore, 
thought that the relationships here shown to exist between certain 
heritable characters of varieties and their capacity to produce high- 
protein grain .will be helpful to plant breeders and agronomists in 
obtaining such varieties of wheats as will produce high-protein grain 
even under relatively unfavorable soil and climatic conditions. 
