62 



THE WATER-SUPPLYING POWER OF THE SOIL 



Shive and Livingston.^ The proportions of the two soils were meas- 

 ured by dry volume, without packing. Sand similar to that here used 

 has, according to Caldwell,^ a moisture-holding capacity of 30.86 per 

 cent of its dry weight. The corresponding percentage for the loam 

 used by Shive and Livingston was 57.32, and that for the mixture as 

 here used was 32.02, the last two data being taken from the paper of 

 Shive and Livingston. 



A further characterization of the soil, suggested by ^ Livingston 

 (1906) and based on its volume when allowed to settle under water, 

 as compared to its dry weight, may be employed here. The soil was 



Fig. 2. — Diagram showing osmometer as arranged to operate against soil. 

 The membrane is held against the soil surface by means of the 

 weight, applied through the lever and cord. Surface evaporation 

 from the soil is practically eliminated by cotton packing around the 

 osmometer. 



poured into a cylindrical graduate flask, stirred to a thin paste with 

 water, and then allowed to settle, when the volume was read upon the 

 graduate scale. 100 grams of the soil here used had a water-settled 

 volume of 74.7 c.c. The same weight of soil when poured into a 

 graduate in the dry condition had a volume of 72 c.c. 



^Shive, J. W., and B. E. Livingston, The relation of atmospheric evaporating power to soil- 

 moisture content at permanent wilting in plants. Plant World 17: 81-121. 1914. 

 *Caldwell, J. S. 1913. 



