Investigations at Burlington, Colorado. 



61 



IV. INVESTIGATIONS AT BURLINGTON, 

 COLORADO, IN 1920. 



Crops were also grown during 1920 at Burlington, a station in the short- 

 grass plains of eastern Colorado, having an altitude of 4,160 feet and an 

 average annual precipitation of 17 inches. The crops which were from the 

 same lot of seed as that used at Lincoln, were planted at the same rate per 

 acre and in the same sized plats as those described. In fact, except for the 

 normally later sowing (April 15) due to a later spring at the higher altitude, 

 the experimental plats were duplicates of those at the former station. The 

 soil is a rich, brown, fine sandy loam, very compact and hard when dry. It 

 has a water-holding capacity of 65 to 70 per cent to a depth of 4 feet. At a 

 depth of 2 to 2.5 feet it is underlaid with a so-called hardpan. Soil analyses 

 show that the concentration of colloidal clay and carbonates in the subsoil 

 is sufficient to give rise to a hardpan, i. e., a much more compact stratum 

 of soil relative to that above or below it, upon its becoming completely 

 dried out (Weaver and Crist, 1922). An examination of table 15 shows 

 that silt constitutes about one-third of the soil at all depths, while the sand 

 decreases and the clay increases in amount to 4 feet. 



Table 15. — Mechanical analyses of soils from Burlington, Colorado. 



Depth of sample, in feet. 



0.0 to 0.5 0.5 to 1.0 



Coarse gravel i 



Fine gravel 



Coarse sand 



Medium sand 



Fine sand 



Very fine sand 



Silt 



Clay 



Hygroscopic coefficient. . . 



p. ct. 



0.0 



0.0 



0.0 



0.13 



2.6 



48.6 



33.4 



15.3 



10.9 



p. ct. 



0.0 



0.0 



0.0 



0.14 



2.2 



49.1 



32.5 



16.1 



10.9 



1 to 2 



p. ct. 



0.0 



0.0 



0.0 



0.17 



1.9 



46.7 



32.0 



19.3 



12.2 



2 to 3 I 3 to 4 



p. ct. 



0.0 



0.0 



0.0 



0.13 



1.5 



45.5 



31.0 



21.9 



12.0 



p. ct. 



0.0 



0.0 



0.0 



0.10 



0.9 



42.2 



34.2 



22.6 



11.4 



Chemical analyses show that carbonates are practically absent in the 

 surface soil, but increase rapidly with depth, and in the hardpan layer, which 

 appears somewhat chalky in color, they often reach concentrations of 5 or 6 

 per cent. Table 16 shows that the soils are not acid, the carbon dioxide 

 increasing very rapidly with depth and being very high at 2 to 4 feet. These 

 soils are rich in phosphorus and potassium and have a sufficient supply of 

 nitrogen. Thus, all the critical elements are present in abundance. 



Hardpan is found rather generally throughout the short-grass plains asso- 

 ciation. The native short-grasses compact the soil so firmly that run-off 

 is usually high, while the water penetrates very slowly. This is indicated 

 by the frequent occurrence of dry stream-beds of various sizes. Shantz 

 (1911) has shown that the average run-off from the short -grass sod at five 

 stations in this region was 37 per cent of the total rainfall (maximum 55 per 

 cent), while that from variously tilled crop areas was almost as great. After 



