Apr. 1, 1918 Capacities of Soils for Irrigation Water 29 



and filling it with water from a graduated cylinder. A special rubber 

 tube ha\dng a diameter of 2X inches and a length of 6}4 feet was secured 

 and determinations were made of the volume weight as follows : Borings 

 were made with the 2-inch auger above described to a depth of i foot, the 

 soil being placed on an oilcloth and then into a suitable bag. The 

 closed spherical end of the rubber was then forced into the hole upon 

 the rounded end of a pole i>2 inches in diameter. Water was poured 

 from a full i,ooo-c. c. graduate cylinder into the tube until it was filled 

 to a point flush with the surface of the soil.^ 



The w^ater was then drawn out of the tube by means of a small pump, 

 after w^hich the tube was taken out of the hole and dried. Then the 

 borings were continued to a depth of 2 feet and the volume of the hole 

 again determined, the volume of the section from i to 2 feet being 

 obtained by difference. This process was continued until the six upper 

 I -foot sections had been studied. The materials used are shown in 

 Plate I, A. The soils were oven dried and w^eighed. The volume of 

 the rubber tube, 200 c. c, was taken into account in the determination 

 of the total volume occupied by the undisturbed soil. 



Laboratory volume-weight determinations were made upon the dis- 

 turbed soil as follows: Brass tubes 2 inches in diameter and 10 inches long 

 were filled with thoroughly pulverized air-dry soil on the Bowman com- 

 pactor. The weight of the soil was corrected for hygroscopic moisture, 

 and the volume of the tube was computed and also determined by filling 

 it with water. 



The volume weights of the upper 6 feet observed by the two methods 

 are set forth in Table XI, in the last column of which the percentage 

 decrease in volume weight caused by disturbing the soil is given. These 

 percentages show great variation, which was not unexpected. The 

 volume weight of the clay soil of the Willows experimental tract was 

 decreased nearly 23 per cent by being disturbed, while that of Wigno 

 tract (fine sandy loam) was increased 15 per cent. The most striking 

 factor brought out by the study of the volume weight of the soil in 

 place as presented in Table XI is the fact that the coarse-textured soils 

 have in general much lower volume weights than the fine-textured 

 ones, a relation just the reverse of that which is generally believed to 

 exist between texture and volume weight. 



' In using a 6-foot rubber tube for the first, second, and third foot sections, some difficulty was experienced 

 in deterunining this point accurately. This difficulty could be overcome by providing several tubes of 

 different lengths. For example, if it is desired to make a volume-weight determination of each foot section 

 to a depth of 6 feet, the first tube used should be about i6 inches in length, the second 28, the third 40, and 

 soon. 



