Investigations at Lincoln, Nebraska. 



45 



developed one or two tillers. Root counts of a large number of individuals 

 gave a total of 16 to 27 per plant. Several roots were traced to a maximum 

 depth of 2,7 feet, the average maximum depth being about 2.3 feet. The 

 average lateral spread was only 6 inches, although some roots extended hori- 

 zontally or obUquely away from the plant to a distance of 7 or 8 inches. 

 The working depth had reached the 1.5-foot level. Besides the greater num- 

 ber of primary roots, their wider spread, and deeper penetration, there was a 

 greater development of laterals, both in number, length, and secondary 

 branching. Many of the younger roots near the soil surface spread laterally 

 only 3 or 4 inches; in general, the widest-spreading roots ended in the surface 

 4 to 8 inches of soil. In the first 8 to 12 inches of soil the abundant laterals 

 sometimes reached a length of 0.2 to 2.5 inches; secondary branches were few 

 and seldom more than 0.3 inch long. At greater depths the branching was 

 much poorer and the laterals shorter, in fact, the last 6 to 12 inches of the 

 thick, straight, white root-ends were devoid of branches (fig. 19). 



The fourth examination was made on June 19 and 21, when the plants, 

 now 80 days old, were beginning to blossom. They had an average height 

 of about 2 feet, although some were 4 inches taller. Many of the plants had 

 only 1 stem, others had from 1 to 5 tillers each, while perhaps 2 was an 

 average. 



Table 10. — Water-content in excess oj hygroscopic coefficient in the crop plats at Lincoln, 1920. 



June was an unusually favorable month for crop growth. 8 to 16 per cent 

 of available water occun-ed in the 0.5 to 5 foot soil-level, wliile drought con- 

 ditions in the surface 0.5 foot were approached only during the latter part 

 of the month, following the interval under consideration and when the grain 

 was ripening (table 10). On June 3, soil temperatures in the oat plats at 

 a depth of 0.5 to 2 feet ranged from 69° to 52° F. The graphs of soil and air 

 temperatures, as well as that of humidity, indicate favorable growth condi- 

 tions (fig. 20). Throughout the period the evaporation rate averaged about 

 20 c. c. per day (table 11). 



