Investigations at All Stations. 



79 



by April 25 root activity was confined largely to the first foot or two of soil, 

 while on June 10 the oats plat was much drier to 4 feet than the control. It 

 should be stated in this connection that the potatoes did not exhaust the 



Table 21. — Water-content in excess of hygroscopic coefficient, Peru, 1921. 



soil-moisture in any degree comparable with that of the oats. The potato 

 plats on June 25 had 2.5 to 10 per cent more available water-content than 

 the oats. 



The temperatures under which root growth occurred are given in table 22. 



Table 22. — Soil-temperatures at Peru, 1921. 



The relative root development of the mature crops during 1921 is compared 

 with that of 1919 in table 23. 



From table 23 it may be seen that the oat roots penetrated more deeply 

 than in 1919, which is the only exception to the smaller cereal crops being 

 somewhat less deeply seated in 1921. These differences are probably due 

 in part to the direct effect of soil-moisture upon root development, the 

 deeper soils being less moist than during 1919, while the maximum amount 

 of water occurred at 1 to 3 feet. It seems probable, also, that there is some 

 correlation between the development of the above-ground parts, which were 

 poorer during 1921, and root extent. It has been pointed out that the oats 

 made the best aerial growth of all the smaller cereals. The only differences 

 in general root habit of these cereals from those grown in 1919 were a less 

 marked development of the roots into a superficial and a deeply penetrating 

 portion and the fact that root-hairs were much more abundant on the root- 

 ends in the drier soils of 1921. 



