80 



Development and Activities of Roots of Crop Plants. 



The potatoes examined had 53 and 60 roots respectively. The horizontal 

 spread of the roots in the earUer stages of growth was very marked. The 

 tendency of these roots to turn rather vertically downward at a later period 

 was not so great during 1921 ; perhaps not more than 30 per cent of the roots 

 penetrated far beyond the 1.5 to 2 foot level. At the time of examination 

 (June 25) the soil-level with the maximum water-content occurred at 1 to 

 2 feet, the soil being drier both above and below this depth. This may 

 account for the root behavior. The root-ends were much more branched 

 than in 1919. In all other respects the root habit of potatoes was similar 

 to that described (c/. fig. 11). 



Table 23. — Relative development of crops at Pent, 

 1919 and 1921. 



The corn, although excavated on August 8, 83 days after planting, had 

 reached practically the same extent as regards both height and root develop- 

 ment as that excavated on September 2, 1919. In fact, the lateral spread 

 of roots was 8 inches greater (4.7 feet) than in 1919. However, the last 

 6 or 8 inches of root-tips were still white and unbranched, indicating incom- 

 plete growth. The shallower roots were even more profoundly branched, 

 with 18 to 20 laterals per inch, than those which penetrated deeper. In 

 every way the root habit agreed with that described for 1919 (c/. fig. 9). 



Investigations at Lincoln, Phillipsburg, and Burlington. 



The experimental plats at Lincoln during 1921 were on a level area of 

 soil, the physical and chemical nature of which was almost identical with 

 that of the lowland plats (c/. p. 40). Potatoes had been grown on the area 

 the preceding year. A good seed-bed was formed by plowing and harrowing 

 a few days before hoeing in the crops on March 24. 



At Phillipsburg the crops were grown only a few meters from the 1920 

 plats; the preceding crop was barley. The soil was plowed about 5 inches 

 deep and harrowed on March 24 and the crops hoed in the next day. 



The crop plats at BurUngton also adjoined those where roots had been 

 dug the preceding year. The wheat and oats stubble had been plowed 



