64 BULLETIN 835, IT. S. DEPARTMENT OF AGRICULTURE. 



pack, the movement of moisture into the dry soil the first 3 days was 

 about one-fifth as great as in 71 days. 



The other data in the table show the relatively rapid rate of mois- 

 ture movement the first few days and the slowing down of the rate 

 of movement with the lapse of time. 



These results in connection with previous data for the flumes in- 

 dicate that the larger part of capillary distribution of the water 

 occurs while water is being applied and in the next two or three days 

 thereafter. 



The last two columns of the table, which give data for the heavy 

 Whittier soil, show the very slow and limited capillary movement of 

 moisture in this class of soils. 



In the three boxes containing the Idaho lava-ash soil with rela- 

 tively great capillary power, the movement of moisture up into the 

 dry soil did not extend very far. In the box the wet pack of which 

 contained 25 per cent of moisture the upward movement in 86 days 

 was only 14.25 inches. The field capacity of this soil is from 20 to 

 25 per cent or a little less than the percentage of moisture in the box 

 just considered. 



In the box the wet pack of which contained 14 per cent of moisture 

 the movement of the moisture upward was only 3^ inches in 37 days. 



If the data in Table 43 were plotted as were the data for the 

 flumes the resulting line would have a parabolic form. 



MOVEMENT OF MOISTURE DOWNWARD. 



Table 44 is arranged to show the distance the moisture moved 

 downward in the boxes after various periods of time, the moist soils 

 being placed above the air-dried soils. The table shows about the 

 same conditions as did the previous table, except that the rate and 

 extent of movement of the moisture downward are considerably 

 greater than with the wet soils below the dry. The rate of move- 

 ment downward is in proportion to the initial percentage of moisture 

 contained in the Avet soil. 



In the Riverside soil containing 15 per cent of moisture, or about 

 the field capacit}^, the extent of movement of the moisture at the end 

 of the fourth day is approximately one-half the distance moved in 

 36 days. In the Idaho soil containing 20 per cent of moisture in the 

 wet pack the moisture had moved in 36 days only about two and one- 

 half times as far as it had at the end of 4 da} 7 s. In the heavy 

 Whittier soil the movement of the moisture even with a moisture con- 

 tent in the wet pack equal to or greater than the field capacity is 

 very slow and does not move to any great distance in 30 days. The 

 data of this table, if plotted, as were the other data, would give a 

 curve resembling a parabola. 



