60 Development and Activities of Roots of Crop Plants. 



tion was about 5.8 feet. The long, glistening-white, unbranched root-ends 

 in the deeper soil were very characteristic. The soil was quite moist to 

 all depths examined, about 8 feet. 



Alfalfa, Medicago sativa. 



The root development of this crop was studied at the same time as that of 

 the cereals. On June 9 the plants were from 4 to 5 inches in height and grow- 

 ing vigorously. The stand was fairly uniform. Numerous tap-roots were 

 found terminating at depths of 2 to 2.7 feet and the soil was well filled with 

 roots to the 1.3-foot level. Tubercles were abundant. The branching 

 habit, number of laterals, etc., were so nearly identical with that described 

 at Lincoln that further description is unnecessary (c/. fig. 24 a). 



By July 10 the larger alfalfa plants were 14 inches tall and in good condition; 

 a few were beginning to blossom. Although the surface 1.5 feet of soil was 

 quite dry, the deeper soil was moist to the maximum depth of root penetration, 

 about 5 feet, and, in fact, for several feet beyond. As at Lincoln, the absence 

 of large lateral branches was a characteristic feature of the root habit, which 

 agreed in all essentials with plants of similar age described at the former station. 



Sweet Clover, Melilotus alba. 



When sweet clover was first examined (June 10), the tallest plants were only 

 3 inches high and the average height of the crop was only 2 inches. However, 

 the underground parts were well advanced in development. The surface 1.7 

 feet of soil was well filled with roots and an average maximum depth for many 

 plants was 2.5 feet. Two especially deep ones penetrated to the 3-foot level. 

 All of the numerous laterals, which were similar to those at Lincoln in number 

 and extent, were well suppUed with nodules. 



On July 9, when the crop had reached a height of 1.3 to 1.7 feet, a second 

 examination was made. The above-ground parts were greatly exceeded in 

 extent by roots. Some of the larger tap-roots were 6 or 7 mm. in diameter 

 and reached depths of 4.5 to 5.7 feet. The long, vertically descending, and 

 unbranched root-ends were developing rapidly in the moist subsoil {cf. fig. 25 b). 



Summary of Crop Development. 

 The crops at PhilUpsburg were planted later than at the other stations and 

 before harvest were badly injured by a rust epidemic which materially re- 

 duced the yield. Early spring conditions were favorable to growth and the 

 stand in every case was quite uniform, the cereals tillered well, and the crops 

 developed rather uniformly and more rapidly than those planted earlier at the 

 other stations. Oats, wheat, and barley, when matured, averaged 2.6, 2.3, 

 and 2.4 feet in height respectively, while the height of alfalfa and sweet clover 

 was 1.2 to 1.7 feet. Responding, apparently, to the environment during 

 June and July, which coupled high water-loss with a relatively dry surface-soil, 

 the crops developed root systems which extended far into the deeper moist 

 soils. Thus, the roots of wheat and oats penetrated to about 6 feet and those 

 of barley even deeper. Alfalfa and sweet clover, when only 64 days old, 

 reached depths exceeding 5 feet. The abundance of laterals, degree of branch- 

 ing, and general root habit corresponded otherwise with crops grown in less 

 arid regions. These results are not at variance with those obtained at the 

 same and neighboring stations during 1919, and also check well with the 

 root habits of the native mixed-prairie vegetation. 



