INDIRECT DETERMINATION OF THE WILTING COEFFICIENT. 61 



as ordinates and the corresponding moisture equivalents as abscissas. 

 The graph is a straight line passing through the origin, and the slope 

 is the reciprocal of 1.84. 



APPLICATION OF INDIRECT WILTING-COEFFICIENT DETERMINATIONS 

 TO THE INTERPRETATION OF FIELD MOISTURE DETERMINATIONS. 



The value of the wilting coefficient as calculated from the moisture 

 equivalents is shown in connection with the following field deter- 

 minations of soil moisture made at Akron, Colo., in 1910. 1 



The data presented graphically in figure 8 represent daily moisture 

 determinations in 1-foot sections to a depth of 6 feet in a soil in which 



30 

 28 

 26 

 24 

 k22 



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8 

 6 



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2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 A 

 MO/STURE £QU/VALENT. 



2 44 46 43 50 52 54 56 68 



Fig. 7, 



-Chart showing the linear relationship between the wilting coefficient and the moisture equivalent 

 for 28 types of soil ranging in texture from coarse sands to the heaviest clays. 



Kubanka wheat, G. I. 1440, was growing. The determinations are 

 of special interest, owing to the fact that the total rainfall during the 

 seven weeks represented in the chart was only 1.09 inches and was 

 distributed in five showers, as follows: June 25, 0.31 inch; June 30, 

 0.05 inch; July 2, 0.30 inch; July 5, 0.38 inch; July 22, 0.05 inch. 

 Total, 1.09 inches. None of these rains penetrated beneath the 

 layer of air-dried surface soil. The rainfall during the whole period 

 can, then, be eliminated so far as its influence upon the available 

 moisture is concerned. 



The following field notes show the stage of development and con- 

 dition of the crops during this period: 



June 9. Sampling started; average height of leaves at this time, when extended 

 8 inches; average dry weight per stem, 0.6 gram. 



June 21. Very dry; plants not wilted but color seems lighter; awns just coming 

 through; lower leaves and small plants drying up rapidly. 



June 24. Heads just out of the boot. 



1 See also Shantz, H. L. Natural Vegetation as an Indicator of the Capabilities of Land for Crop Pro- 

 duction in the Great Plains Area. Bulletin 201, Bureau of Plant Industry, U. S. Dept. of Agriculture, 

 1911, pp. 30-33. 



230 



