Investigations at All Stations. 85 



many leaves as the taller ones at the other stations. Plate 7 shows the 

 relative development of wheat and barley on June 10, while the oat plats 

 at the several stations are shown in plate 8. 



Rainfall during this period (May 20 to June 10) was 4.0, 5.7, and 1.7 

 inches at Lincoln, Philhpsburg, and Burhngton, respectively. The water- 

 content of the soil is given in table 25. The well-watered soil at all depths 

 at Lincoln (13 per cent or more) contrasts strikingly with the drier subsoil 

 at Philhpsburg (5 per cent or less) ; while at Burhngton scarcely 2 per cent 

 was available in the first foot and none deeper. However, during the inter- 

 vening period (May 28), conditions were shghtly better, with 4 to 7 per cent 

 available moisture in the surface foot at Burhngton, while moisture relations 

 at Philhpsburg were similar to those indicated in the table. At no time 

 at Lincoln was there a period of drought, well-distributed and ample rainfall 

 keeping the soil moist. 



The average soil-temperature at a depth of 3 inches was highest at Philhps- 

 burg (68° to 72° F.), intermediate at Lincoln (66° to 68° F.), and lowest 

 at Burhngton (65° to 68° F.). The daily range at Burhngton (16° to 20° F.) 

 was shghtly greater than at either of the other stations. After June 16 all 

 of the soil thermograph-bulbs were placed at a depth of 18 inches. At this 

 level the weekly fluctuations did not exceed 2° or 3° F., except in the drier 

 soils at Burhngton, where they were 4° or 5° F. At this depth the average 

 weekly temperatures at Philhpsburg varied from 74° to 76° F. (June 16 to July 

 3) , at Lincoln 70° to 72° F. , and at Burhngton 66° to 73° F. The temperatures 

 at greater soil-depths are given in table 26. It seems clear from these data 

 that differences in soil-temperatures at the several stations are so small that 

 they exert httle effect upon crop-growth, especially after the seedhng 

 stage has been past. Air-temperatures at ah the stations were very much 

 higher than during the preceding interval, but the same general relation with 

 highest temperatures at Lincoln and the lowest at Burhngton prevailed. 

 An exception to this was the shghtly warmer nights at Philhpsburg during a 

 part of the period (fig. 37). Night temperatures at Burhngton continued 

 low (averages, 55° to 59° F.), the thermograph-pen sometimes falhng to 

 42° F. The evaporating power of the air during the last week in May was 

 practically the same (22 c. c.) at aU the stations, but otherwise much higher, 

 as usual, at Burhngton (fig. 38). 



The crops ripened at Lincoln and Philhpsburg at practicaUy the same time. 

 On June 22 and 23, when they were in the early dough stage, the barley alone 

 being somewhat further advanced in development, the roots were examined 

 and several representative meter-quadrats of each plat were harvested. 

 The crops at Burhngton, which were considerably damaged by grasshoppers, 

 had reached a similar stage of development when they were harvested on 

 June 30. The sheaves were shipped to Lincoln, where all were thoroughly 

 air-dried in one of the University of Nebraska botanical laboratories, and 

 finally weighed. 



Rainfall at both Lincoln and Philhpsburg was hght during this interval 

 (0.4 inch or less). This is reflected in the water-content of the soil shown 

 in table 25. In this connection it should be pointed out that even when the 

 crops were mature the soil at a depth of 4 to 7 feet was very moist at Lincoln 

 (18.5 per cent) and less so at Philhpsburg (11.1 per cent). This condition 



