Investigations at Peru, Nebraska. 



35 



of the several plats are apparent, except that the oat plats were drier in the 

 surface 6 inches, and those of corn showed more available water at all levels 

 to 3 feet than the cereals which were planted earlier. At this time the latter 

 were about 12 inches tall, and, although the main development of roots was 

 in the surface 2 feet of soil, not a few extended into the third foot or beyond 

 (cf. figs. 1 a, b and 3 b, c). The younger corn plants had rooted much 

 more superficially, and the total transpiring surface was less extensive than 

 in the smaller cereals at this time. However, from the uniformity of the 

 water-content in the third foot, it seems clear that little absorption had 

 occurred at this level. The water relations of the soils in the several plats 

 on June 23 are shown in figure 14. The small percentage of available water 

 at all levels, when compared with conditions on May 30, is at once evident, 

 and shows clearly that the roots were probably extracting water at depths 

 of at least 3 feet. 



It is interesting to compare the water-content of the oat plats with that 

 of wheat and barley. On June 23 the average water-content of the two 

 oat plats was only 70 per cent of the average of the two wheat plats, and 65 

 per cent of that of the barley plat. Five days later, on June 28, the average 

 water-content of the oat plats was 76 per cent of the average of the wheat 

 plats and 77 per cent of that of the barley plat. In other words, on June 

 23 the oat plats contained 30 per cent less moisture than the wheat plats and 

 35 per cent less than the barley. On June 28, the oat plats contained 24 

 per cent less moisture than the wheat and 23 per cent less than the barley. 

 This agrees well with the root habit. A comparison of the mature root sys- 

 tems (figs. 2, 4, and 6) shows at once that the number of deeply penetrating 

 roots of oats is 1 or 2 greater per plant than that of wheat and 3 or 4 greater 

 than that of barley. It is also possible that oat roots are more efficient 

 absorbers than those of wheat and barley. 



OATS OATS BARLEY WHEAT WHEAT CORN 



























J'-z' 















**** " 







Fig. 14. — Water-content in excess of hygroscopic coefficient 

 in the several plats on June 23. 



The relative available water-contents of the potato and corn plats are also 

 significant. On June 28, at practically every level represented, the potatoes 

 had exhausted the soil-moisture more completely than had the corn (table 5). 

 The average of all depths gave 10 per cent less in the potato plat. But 9 

 days later, on July 7, the corn, responding to the ideal growing weather by 

 a very rapid development of the top, had reversed these conditions, for 

 the corn plat now had approximately 10 per cent less moisture than the potato 

 plat. A week later, July 15, this difference had increased to 19 per cent. 

 Another factor occurring during this two-week period may have had some 



