38 EXPERIMENT STATION EECORD. [VoL 37 



cultivation of tobacco soils, with special reference to the maintenance of soil 

 fertility. The decreased yield and quality of tobacco grown on " sick " soils, 

 due to the presence of the root rot disease (Thielavia basicola), is emphasized 

 and control measures recommended. 



A study of Colorado wheat, III, W. P. Headden (Colorado Sta. Bui. 219 

 (1916), pp. 3-131).— In continuation of previous Avorli (E. S. R., 3o, p. §32), 

 the author presents data relative to the composition of Colorado wheats in 

 general, and the results of studies of the effects of fertilizers, of water, and of 

 climate upon the composition of wheat. Defiance, Red Fife, and Kubanka 

 wheats grown in the seasons of 1913, 1914, and 1915 under known conditions 

 form the basis for the analytical results obtained. 



The results served to show that Colorado wheats contain large percentages 

 of nitrogen and of true gluten. The ratio of gliadin nitrogen to glutenin 

 nitrogen falls well within the limits accepted for good flours. On the other 

 liand, some samples were low in nitrogen but had a fair gliadin-glutenin ratio. 

 Samples grown under dry-farm conditions were not found to be superior to 

 those grown unrler irrigation. 



The factors which determine the wheat crop are given as distribution of 

 rainfall ratlier than quantity, the degree of cloudiness, resistance of the plant 

 to rust, the stage of development of the plant when attacked, temperature, and 

 soil fertility. 



The character of the wheat grain is deemed much more easily influenced by 

 soil fertility than is generally supposed, and the individual plant food elements 

 exercise specific Influences upon its composition. The nitric nitrogen in the soil 

 affects the growth of the plant, Increasing the nitrogen content of both the 

 plant and the seed. Nitric nitrogen also Influences the composition and char- 

 acter of the grain, producing the characteristic " hard '* wheat. These char- 

 acters are believed to liave a deeper significance In the plant metabolism than 

 the production of an Increase of a few tenths of one per cent In the nitrogen 

 content of the berry. The mineral constituents contained In the berry are Influ- 

 enced by the amount of nitric nitrogen available to the plant, as are those in 

 the plant Itself, but in the latter instance to a different extent and not neces- 

 sarily in the same direction as In the berry. Furthermore, nitric nitrogen 

 produces a soft, weak straw, causing lodj:ing both from a production of a heavy 

 growth of leaves and elongation of the upper parts of the plant and from a 

 weakness In the lower nodes. It also greatly Increases susceptibility to rust, 

 probably by furnishing a better nutrient and because of the softened condition 

 of the plant. Organic nitrogen in farmyard manure does not produce these 

 results, except as It Is converted Into nitric nitrogen, the rate of which process 

 depends upon the nitrifying power of the individual soils. 



The investigations with potassium Indicate that that element has no positive 

 effect on the quantity of starch produced. Potassium has a tendency, however, 

 to suppress the nitrogen content of the berry, and it suppresses that of the 

 plant, particularly In the stems and leaves, throughout Its growing period, but 

 does not appear to suppress that of the head. Potassium stimulated growth at 

 a certain stage of development, but the plants on the other plats attained the 

 ftn.me degree of development a few days later. It apparently increases yellow 

 berry. 



Phosphorus has produced no definite effect. The phosphorus in the berry 

 was depressed by nitric nitrogen but was not affected by potassium. 



Manganese was uniformly present. 



The amount of irrigation water applied may Increase yields but has prac- 

 tically no effect upon the composition of the crop. The leaching effect of 

 irrigation water on the nitrates is not sufficient to affect the nitrogen content 



