76 
Research Bulletin No. 5 
water stops. During the summer the crop uses this water. The 
fifteenth foot is, however, close enough to the sheet water so that 
there is a constant supply rising within the soil zone occupied 
by the lower roots of the alfalfa. It should be remembered that 
this rise of water into the lower levels shown in Table 29 is due 
to the presence of sheet water only a few feet below, so that the 
upward rise of water in this soil does not in any wiay diminish 
the per cent of water in the soil immediately below it and that 
this action would cease very soon after the free water was ex- 
hausted. 
The soil in this field has not been dried in any section as dry 
as the same section in the alfalfa field on the table-land. The 
plants seem to find it easier to raise the water from below than 
to take more from the soil in the intermediate sections. During 
the years 1910 and 1911 a field of alfalfa on the table-land died 
for lack of moisture. The alfalfa was seeded in 1902 and was 
well established in the soil. During the same years the alfalfa 
on the bench not only lived thru but produced almost normal 
crops of hay. 
In Table 29 was shown the effect of capillarity when operat- 
ing just above a constant supply of free water. Under these 
conditions the force was very active and within certain limits 
would be a great factor in crop production. In Table 30 are 
given data to show its effect when removed from a supply of free 
water. In this table the fourth foot of soil is shown to be prac- 
tically dry from June, 1910, to July, 1911. The fifth foot con- 
tains about four per cent more water, and is only three or four 
per cent below saturation. We do not find, however, that any 
water is drawn from the fifth foot to replace that which had been 
used by the crop from the fourth foot. Even in a period of seven- 
teen months the content of either foot remains very little 
changed. In fact we have abundant proof that capillary move- 
ment is feeble in soils that are dried any considerable extent 
below the saturation point. The evidence indicates that, in the 
main, the plant roots, to obtain water, extend themselves into the 
soil zone where available water is present, rather than depend 
upon the water being brought to them by capillarity. 
