58 



Development and Activities of Roots of Crop Plants. 



grown at Lincoln. In fact, the similarity was so great in case of the cereals 

 that detailed descriptions need not be given. The lateral spread was about 

 5 to 7 inches. The working depth was 2.1 feet. One root was traced to a 

 maximum depth of 3.8 feet and several were found at the 3.5-foot level. 

 Below 2.6 feet the thick, white roots were entirely devoid of branches. Thus 

 the root system was more deeply seated than that of oats at Lincoln on May 30. 



Table 13. — Water-content in excess of hygroscopic coefficient in crop plats at Phillipsburg, 



Kansas, 1920. 



Date. 



to 0.5 foot. 



0.5 to 1 foot. 



1 to 2 feet. 



2 to 3 feet. 



3 to 4 feet. 



May 7 



June 2 



June 10 



June 24 



July 1 



July 9 



July 21 



Aug. 4 



Aug. 26 



Wilting coefficient 



Hygroscopic coefficient 



16.8 



9.7 



9.1 



8.5 



-0.4 



-3.1 



-3.3 



2.3 



0.1 



16.7 



12.2 



13.0 



7.6 



0.9 



2.5 



-1.2 



4.0 



1.5 



15.8 



12.7 



11.2 



9.0 



2.9 



0.9 



-0.4 



2.5 



-2.1 



12.6 

 12.8 



10.3 



1.3 



0.4 



2.2 



-0.9 



11.0 

 12.4 



3.9 

 0.9 

 2.1 

 0.9 



13.3 

 10.6 



13.3 

 10.6 



13.4 

 10.9 



13.5 

 10.6 



13.1 

 10.7 



On July 9 the oats was well past the dough stage of grain development. 

 The crop averaged 2.6 feet in height. Counts on selected square-meter areas 

 showed that the plants had an average of 2.3 tillers each. The crop was 

 sUghtly damaged by grasshoppers and also somewhat affected by stem rust, 

 Pucdnia graminis avence. Indeed, by the time of harvest (July 20) the rust 

 epidemic was so severe that the grain was very hght and of very poor quality. 



Table 14. — Average daily evaporation at Phillipsburg, Kansas, 1920. 



June 2 to 10 11.0 



June 10 to 17 26.9 



June 17 to 24 12.3 



June 24 to July 1 24.5 



July 1 to 8 32.2 



Julys to 15 30.6 



July 15 to 21 25.9 



July 21 to 28 29.6 



July 28 to Aug. 4 21 . 1 



Aug. 4 to 11 13.8 



Aug. 11 to 18 13.0 



Aug. 18 to 26 24.2 



The root system by this time had penetrated the loess soil to a working 

 depth of 3.3 feet. A maximum depth of 6 feet was recorded for a few of the 

 longest roots, while at 5.5 feet depth they were not at all uncommon. Thus, 

 the root depth exceeded that at Lincoln (4.2 feet) and nearly equaled that 

 at Peru (6.7 feet). The root extent was greater than that of Texas Red oats 

 (4.8 feet) excavated a few miles distant, but in similar soil, in June 1919 

 (Weaver, 1920 : 119). 



The clue to this marked root development is apparently to be found in 

 an examination of the texture and water-content of the soil and the aerial 

 conditions causing water-loss. In general, the mellow soil during this interval 

 was relatively dry when compared with conditions at Lincoln, while the 

 evaporating power of the air was greater than at the latter station. This 

 seems to have stimulated root-growth in the deeper soils where available 



