Investigations at Burlington, Colorado. 



75 



June, while during the remainder of the season a deficiency at all levels was 

 not uncommon. 



Soil temperatures at a depth of 6 inches were highest at Lincoln (70° to 

 77° F.), and lowest at Burlington (64° to 72° F.) during the first half of June, 

 but by the last week in June this relation was reversed, the soil at Burlington 

 remaining warmest throughout the season. The average weekly differences 

 were often 6° to 8° F., the Lincoln soil being coldest, that at Phillipsburg 

 intermediate, while the dry soils at Burlington had the highest temperature 

 (fig. 33). 



The average daily air-temperature throughout the season was usually 

 5° to 7° F. colder at Burlington than at Phillipsburg, while that at Lincoln was 

 generally higher than that at Phillispburg (fig. 34). 



The average day humidity at Lincoln ranged between 49 and 65 per cent 

 and was usually higher than that at Burlington. However, the average night 

 humidity at Lincoln (67 to 82 per cent) was usually exceeded by that at 



June July August 



2 3 4 1^ 3 412 3 4 



L. J 1 I 1 ' 1 1 1 ' 1 ' 



Fig. 36. — Average daily evaporation at Lincoln (solid line), Phillips- 

 burg (long broken lines), and Burlington (short broken 

 lines), 1920. 



Burlington by about 8 per cent until late in July (fig. 29). Conditions at 

 Phillipsburg were intermediate. The much greater daily range of both 

 temperature and humidity at the Burlington station when compared with 

 that at Lincoln is shown in figure 35. This combination of high temperature 

 and low humidity, which occurs rather regularly in the afternoons at Bur- 

 lington, when coupled with dry soil, are conditions very unfavorable for plant- 

 growth. 



Wind movement is much greater at Burlington than at either of the other 

 stations and is an important factor in desiccating both crops and soil. An 

 average day velocity of 8 or 10 miles per hour (at a height of 0.5 meter) is 

 quite usual, while periods lasting for several days when the velocity reaches 

 20 or 30 miles per hour are not uncommon. The amount of wind is less at 

 PhiUipsburg and much less at Lincoln (for example, 4 miles per hour average 

 daily from July 13 to September 19, 1916 (c/. Weaver, 1919 : 23). 



