ROOT GROWTH 39 



Corn, which is merely a giant form of grass, has a fine, fibrous 

 root system, like all members of the grass family. The root system 

 is not characterized by any tap root such as is found in clover. 



In the early stages the roots develop laterally. The North Dakota 

 Experiment Station found that *30 days after planting the roots from 

 adj-acent stalks had met and interlaced, and that most of the roots 

 were within the first eight inches of the surface of the soil and that 

 few had penetrated to a depth of 12 inches. Six inches from the hill 

 the main roots lay 2^ inches below the surface, while midway be- 

 tween the hills, they were 4J4 inches below the surface. The latter 

 point should be especially noted, for it is a strong argument in favor 

 of shallow cultivation. 



An examination 55 days after planting, at the last cultivation, 

 when the plants were 4j4 feet high, showed that the main roots had 

 reached a depth of 23^ feet. Many of the lateral roots extended the 

 entire distance from hill to hill (three feet eight inches), inclining 

 most of the way, and when about 3 to 3^^ feet from the hill dropping 

 almost vertically downward. The lateral and vertical roots gave 

 off numerous branches which rebranched again and again, filling the 

 soil to a depth of two feet with a perfect network of roots. The lateral 

 roots sent up numerous vertical feeders to within two inches of the 

 surface. 



At 90 days from planting, or soon after the frost had killed the 

 corn, another sample showed that the ground to a depth of 3^ feet 

 was fully occupied by roots. The conclusions were that after corn is 

 ten inches high, it should not be cultivated deeply because of injury to 

 surface roots. 



PRIMARY AND SECONDARY ROOTS. The roots which 

 arise from the base of the stalk are called "primary" roots. Often in 

 this same class are also placed those springing from the first two or 

 three nodes. The "secondary" root system appears in checked corn 

 during the time of "laying by;" that is, when the winds of summer 

 begin to "jostle" the corn plants. In trying to support themselves 

 these roots are sent out. They may appear on nodes as high up as 

 the seventh, and in listed corn, even higher. These roots do not usu- 

 ally appear on more than two nodes above the ground. They act both 

 as guys and stays. Before entering the soil a small enlargement 

 forms at the end. On entering a moist soil this thickened portion 

 becomes mucilaginous and may be an aid in holding the root in the 

 soil until it forms a little bunch of roots of its own. The brace roots 

 aid in the support of the plant and absorb small quantities of plant 



♦Bulletin 43, N. D. Experiment Station. 



