Investigations at All Stations. 



87 



An exception to this occurred in the case of the number of heads of wheat 

 at Burlington when compared with PhiUipsburg, while the difference in this 

 respect in the case of barley was small. However, a clear gradation in the 

 reduction of total dry weight from east to west is apparent. Root 

 extent, whether working depth or maximum penetration, is least at Burling- 

 ton, intermediate at Lincoln, and greatest at PhilUpsburg. As pointed out 

 elsewhere (p. 76), the very deep root penetration at PhilUpsburg is thought 

 to be due to an unusually high water-content of the mellow loess soil and 

 especially the deeper subsoil. 



Summary of Environment and Crop Development. 



The season of 1921 was one of drought at the Peru station. A deficiency 

 of rainfall, coupled with poor distribution, resulted in a much drier soil than 

 in 1919, especially the deeper subsoil. The stands of oats, wheat, and barley 

 were thin, the plants having tillered poorly, and the height-growth, which 



Fig. 39. — Mean precipitation in inches (black) and precipitation for 1921 

 at Lincoln (left), PhilUpsburg, and Burlington. 



varied from 2 to 2.4 feet, except in the case of barley, was 6 to 8 inches less 

 than in 1919. The root systems, except in the case of oats, were somewhat 

 less deeply seated than in 1919, reaching working depths of 4 feet and having 

 a maximum depth of 6.1 to 6.6 feet. Oat roots were traced to depths of 

 8 feet. All of the smaller cereals showed a less marked development of the 

 roots into a superficial and a deeply penetrating portion than in 1919. Potato 

 roots, while very similar in distribution to those of 1919, showed a lesser 

 tendency to turn downward at a later period in their development. This, 

 like the lesser penetration of the roots of the cereals, may be due in part to 

 the fact that the largest supply of available water occurred in the 1 to 3 foot 

 level. Corn, although examined on August 8, had reached the same height 

 (8.5 feet) and had approximately the same root depth as on September 2, 



