26 



Development and Activities of Roots of Crop Plants. 



2 to 3 feet beneath the opposite hill." The corn in this case was level-planted. 

 In examining the mature corn 125 days after planting, the stalks were 8 feet 

 high, the roots "had reached a depth of fully 4 feet, and some were traced to 

 the depth of 5 feet." Shepperd (1905), at Fargo, North Dakota, concluded 

 that "corn roots commonly reached a depth of 3.5 to 4 feet, as is shown by 

 root experiments covering a period of 5 years." Miller (1916) grew Pride of 

 Saline corn at Garden City, Kansas, in sandy-loam soil, irrigated in the fall 

 with 8 to 10 inches of water after plowing. The corn grew in alternate rows 

 with Blackhull kafir and Dwarf milo respectively. The roots were excavated 

 by washing. During the wet season of 1915 they were found to penetrate 

 6 feet deep and to have a lateral spread of 3.7 feet from the base of the plant. 

 During the dry season of 1914, when but approximately one-third as much 

 precipitation occurred during the growing-period of the plants, the depth of 

 penetration was the same, but the horizontal spread was 8 inches less. The 

 tops reached a height of 7 feet in 1915, but in 1914 they did not exceed 6 feet. 



Investigations of corn roots in the United States have been rather limited 

 in extent. In most cases, too, they are somewhat unsatisfactory in regard to 

 the conclusions reached. In fact, except for the work of Miller, this review 

 shows no results in respect to the lateral spread and depth of root penetration 

 comparable to those obtained at Peru. 



Other investigators give data on root extent that are greatly at variance 

 with those found in our studies. These discrepancies may be due in part to 

 varietal and environmental differences, but it is also probable that they may 

 also be attributed in part to incomplete and faulty methods of excavation. 

 Indeed, some of the workers state frankly that the roots were badly broken 

 in the process of separating them from the soil by washing and also in some 

 cases that the roots were not traced to their extremities. 



With reference to the order of root development, our observations coincide 

 very closely with those of Hays, namely, that the first roots grow horizontally 

 and that later both these primary roots and those from the nodes as well 

 take a downward course, the latter from the very beginning. He stated that 

 this change in direction of growth began about the fourth week. At Peru, 

 however, it came later. Even 5 weeks after planting there was no indication 

 of this downward course on the part of the roots. Moreover, the lateral 

 roots had not yet reached the limit of their spread by approximately 2 feet. 

 Hickman and Ten Eyck also noted the later downward turn of the horizontal 

 roots. 



Potato, Solanum tuberosum. 

 The plat in which the potatoes were grown was plowed April 4 to a depth 

 of 6 inches and immediately harrowed. The next day the ground was fur- 

 rowed out with a plow into rows 3 feet apart and planted. In preparing 

 the cuttings the tubers of Early Ohio potatoes were cut so that each piece had 

 from two to three buds, and then all the buds but one in each piece were 

 excised. In this way each hill had but one plant. The pieces of tubers were 

 placed 2 feet apart in the row and were covered to a depth of 3 inches. On 

 May 5 the potatoes, which were just coming through the ground, were har- 

 rowed to level the surface and kill the weeds. On May 31 and again on June 

 16 they were hoed with a garden hoe. Each hoeing was shallow in order to 

 kill the weeds but not to disturb the potato roots lying near the surface. 



