88 Development and Activities of Roots of Crop Plants. 



1919. The root habit was similar to that of 1919, except the lateral spread 

 was 8 inches greater (4.7 feet). 



Crops of oats, wheat, and barley were again grown at Lincoln, Phillipsburg, 

 and Burlington during 1921, in order to check the results obtained at the 

 several stations during the preceding year. The precipitation for the season 

 (March to June inclusive) was 1.5 inches below the normal at Lincoln, 0.9 

 inch above at Burhngton, and 2.0 inches above the normal at PhiUipsburg. 

 Precipitation for March was approximately half or less than half normal at all 

 stations, but April was unusually wet, an excess of 1.8 inches occurring at 

 Burhngton. During May a deficiency of about an inch occurred at both Lin- 

 coln and Burhngton, while Philhpsburg had an excess of an inch. During June 

 1.3 inches and 0.5 inch of rainfall above the normal occurred at Phillipsburg 

 and Burhngton respectively, while the rainfall at Lincoln was about normal 

 (fig. 39). However, the rains at Lincoln were so well distributed that no 

 drought period occurred, while at the other stations these were not infrequent, 

 especially at Burhngton, where much moisture fell in light showers or torren- 

 tial rains. However, the season as a whole was favorable for crop-growth. 



A study of the water-content to a depth of 4 feet (table 25) shows, with an 

 occasional exception in the surface foot, a progressively drier soil from Lincoln 

 westward. At no time during the growth of the crops was there a deficiency 

 of soil-moisture at Lincoln. In fact, a margin of 7.5 to 16 per cent above the 

 hygroscopic coefficient usually occurred. Less favorable conditions existed 

 at Philhpsburg, where the subsoil (2 to 4 feet) at the time of planting had an 

 available moisture-supply of only 3 per cent. This increased during May 

 and June to 5 per cent, but was reduced by June 22 to 1 per cent at 3 feet in 

 depth. The crops at Burhngton had sufficient water above the hardpan 

 (3 to 11 per cent) during April and May, but by June 10 this was reduced to 

 about 3 per cent, and when the crops were ripe on June 30, no available water 

 was present at any depth (cf. Briggs and Shantz, 1912 : 62). 



Average daily soil-temperatures at a depth of 3 inches in the prairie sod 

 ranged from 55° to 60° F. at Philhpsburg from April 28 until May 20 and 

 about 5° F. lower at Burhngton. From May 20 until June 16 the temperature 

 was highest at Philhpsburg (68° to 72° F.), intermediate at Lincoln, and 

 coldest (65° to 68° F.) at Burhngton. Temperatures at a depth of 18 inches, 

 after June 16, although quite constant at any station, were also about 6° F. 

 lower at Burlington, This general relation held to a depth of 4 feet, although 

 differences were so slight that, except in very early spring, they probably 

 have httle effect upon crop development (table 26). The average day air- 

 temperatures (fig. 37) were, as during the preceding season, highest at Lincoln 

 and lowest at Burhngton, while this same general relation held for average 

 night temperatures, those at Burhngton varied from 45° to 67° F, 



The average day humidity, in general, held the same relation as during 



1920, viz, being much higher at Lincoln and lower at Burhngton than at 

 PhiUipsburg. The extremes of temperature and humidity at Burhngton 

 were quite as pronounced as during 1920. The average daily evaporating 

 power of the air at the several stations is shown in figure 38. At Burlington 

 this sometimes reached a maximum of 45 to over 60 c. c, at Philhpsburg 

 28 to 45 c. c, while at Lincoln it did not exceed 18 to 27 c. c. Thus aU of the 

 environmental conditions for crop-growth were most favorable at Lincoln, 

 intermediate at Phillipsburg, and least favorable at Burhngton. 



