July i6, 1917 Movement and Distribution of Moisture in Soil 



131 



Figure 13 shows that in all depths the moisture decreased from May 

 22 to 29 to July 12 to 15, after which it increased because of the rainfall 

 prior to the samplings on July 27 to 29 and August 7 to 9. It will be 

 noticed, however, that precipitations as small as o.io of an inch in early 

 July and middle August did not affect the moisture content of even the 

 first foot. From these dates until August 28 to 30 the percentage of 

 moisture decreased. The variations mentioned were very marked in the 

 first foot and, although there is a similar fluctuation in every foot, a 

 decrease with increase in depth is noticed until at the sixth foot the 

 influence of the season was very slight. Evidently a loss or a gain in the 

 surface foot very soon disturbed the moisture equilibrium to a depth of 

 6 feet, due to the action of capillarity. 



Percenf-age of moisture 



5 6 7 8 9 /O // /! /J f4 /S 16 /7 /3 19 16 _S^ 



Fig. 13.— Diagram showing the effect of dry-farming seasonal conditions on the distribution of moisture 

 in fallow soil to a depth of 6 feet on (i) May 22-29. (2) June 6-10, {3) June 16-20. (4) June 26-28. (s) July 

 J2-I5, (6) July 17-19, (7) July 27-29. (8) August t-9. (9) August 17-19. do) August 28-30. 19x6. The num- 

 bers I to 10. etc.. refer to the columns in the diagram, which were sampled on the dates noted. Each 

 column is the average of 24 samplings. 



LABORATORY STUDIES 

 EFFECT OF INITIAL PERCENTAGE OF SOIL MOISTURE 

 Effect on Upward CAPiti.ARY Movement 

 In order to study the efifect of the initial percentage of moisture in 

 the soil on the upward capillary movement of water, jointed brass tubes 

 8 inches long and i K inches in diameter were filled with Greenville loam 

 containing, respectively, 2%, 5, 10, 15, and 20 per cent of moisture. 

 For each test, columns made by screwing together three of the brass 

 tubes were used. These tubes were held upright in a few inches of water for 

 periods of 24, 48, 72, and 120 hours, at the end of which they were taken 

 down and the percentage of moisture determined for each 8-inch section. 

 In figure 14 the results of this experiment are recorded. The columns 

 in the figure are in the positions the soils were in the experiment, the 

 lowest one being in contact with the water. 



