JOURNAL OF AGRICDLTDRAL RESEARCH 



Vol.. XIII 



Washington, D. C, April, i, 1918 



No. I 



STUDIES ON CAPACITIES OF SOILS FOR IRRIGATION 

 WATER, AND ON A NEW METHOD OF DETERMINING 

 VOLUME WEIGHT 



By O. W. ISRAELSEN 



Associate Professor of Irrigation and Drainage, Utah Agricultural College; at the time 

 this paper was prepared. Instructor in Experimental Irrigation, Division of Irrigation 

 Investigations, University of California 



INTRODUCTION 



In connection with a study of the economical duty of water for alfalfa 

 in Sacramento Valley, California, conducted from 1910 to 1915 as a part 

 of the Cooperative Irrigation Investigations in California ^ certain obser- 

 vations were made, and methods devised which it seemed could be 

 better presented and described in a separate paper than as a part of the 

 general report of the study. It is realized that some of the data pre- 

 sented suggest ideas concerning soil properties which are not fully 

 established by the preliminary investigations here reported. The 

 observations are presented in two parts : (i) Studies on the capacities 

 of soils for irrigation water, and (2) a new method of determining the 

 volume weight of soils. 



PART I.— STUDIES ON CAPACITIES OF SOILS TO RETAIN IRRIGATION 



WATER 2 



THEORETICAL DISCUSSION 



That soil water is held in the form of minute films about the soil parti- 

 cles and in the interstitial spaces is a matter of common knowledge. 

 The maximum capacity of soils to hold water in the capillary form may 

 be limited by the total interstitial space in the soil rather than by the 

 total external surface area of the soil particles {4)} It is therefore 

 obvious that the volume weight of soil in place may be an important 

 indicator of its water-holding power. The various laboratory methods 

 which have been used to determine the maximum retentive power of soils 

 for water usually give results which are far in excess of the retentive 



1 The Cooperative Irrigation Investigations in California are carried on by the Division of Irrigation 

 Investigations, OfiBce of Public Roads and Rural Engineering, United States Department of Agriculture, 

 in conjunction with the California State Department of Engineering and the University of California Agri- 

 cultural Experiment Station. 



2 For a full report of general studies referred to herein, see (r) in " Literature cited," p. 34. 

 2 Reference is made by number (italic) to "Literature cited," p. 34-35. 



Journal of Agricultural Research, 

 Washington, D. C. 



Vol. XIII. No. I 

 Apr. I, 1918 

 KeyNo. Cal. :» 



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