Aug. =8, 1916 Indirect Determination of Hygroscopic Coefficient 845 



SUMMARY 



The hygroscopic coefficient may in most cases be calculated from the 

 moisture equivalent with sufficient accuracy to permit its use in soil- 

 moisture studies. For certain types of soil, however, the ratio departs 

 so widely from that assigned by Briggs and Shantz that the indiscriminate 

 use of the latter value does not seem permissible. Before employing 

 this indirect method for the determination of the hygroscopic coefficient 

 in connection with soil-moisture studies the ratio should be experimentally 

 established for each of the particular types of soil involved. 



The effect of considerable quantities of organic matter is, in general, 

 to give the ratio of the moisture equivalent to the hygroscopic coefficient 

 a higher value. 



In the case of any extensive study of soil moisture involving many 

 soil types the same general conclusions as to the relation of the non- 

 available moisture to the hygroscopic coefficient are to be expected no 

 matter whether the latter value be directly determined or be calculated 

 from the moisture equivalent by the Briggs-Shantz formula. 



For the calculation of the moisture equivalent from the mechanical 

 analysis no general formula appears universally applicable, the formula 

 needing modification according to the soil type to which it is to be applied. 



LITERATURE CITED 



(1) Alway, F. J. 



19 13. vStudies on the relation of the non-available water of the soil to the hygro- 

 scopic coefficient. Nebr. Agr. Exp. Sta. Research Bui. 3, 122 p., 37,fig. 



(2) and McDouE, G. R. 



1916. The loess soils of the Nebraska portion of the transition region: I. Hygro- 

 scopicity, nitrogen and organic carbon. In Soil Science, v. 1, no. 3, 

 p. 197-238, 2 fig., 3 pi. Literature cited, p. 236-238. 



(3) and Rost, C. O. 



1916. The loess soils of the Nebraska portion of the transition region : IV. Mechan- 

 ical composition and inorganic constituents. In Soil Science, v. 1, 

 no. 5, p. 405-436. Literature cited, p. 435-436. 



(4) Briggs, L. J. 



1915. Dry-farming investigations in the United States. In Rpt. 84th Meeting 

 Brit. Assoc. Adv. Sci. 1914, p. 263-282, 7 fig., pi. 5. 



(5) and McLane, J. W. 



1907. The moisture equivalents of soils. U. S. Dept. Agr. Bur. Soils Bui. 45, 



23 p., 1 fig., 1 pi. 



(6) 



191 1. Moisture equivalent determinations and their application. In Proc. Amer. 



Soc. Agron., v. 2, 1910, p. 138-147, pi. 6. 



(7) and Shantz, H. L. 



1912. The wilting coefficient for different plants and its indirect determina- 

 tion. U. S. Dept. Agr. Bur. Plant Indus. Bui. 230, 83 p., 9 fig., 2 pi. 



(8) Hiujard, E. W. 



i860. Report on the Geology and Agriculture of the State of Mississippi. 391 

 p., 6 fig., 2 pi., 1 map. Jackson, Miss. 



