2 BULLETIN 1221, U. S. DEPARTMENT OF AGRICULTURE. 
difference was not uniform, and assuming the column of soil to be 
uniform, this difference could be explained only in one or both of two 
ways: Either the distribution of moisture did not vary uniformly 
from one end of the soil column to the other, or the moisture moved 
upward, not gradually, but in waves. ‘There is reason to believe both 
of these conditions exist; but the purpose here is to consider only the 
distribution of the moisture, the result and not the cause. 
The experiments planned to throw light on the distribution of the 
moisture were conducted at intervals over a period of six years. They 
differed from the earlier experiments in the use of columns of small 
cross section instead of comparatively large columns. The change 
to the smaller columns was not only a matter of convenience, but of 
necessity to insure accurate soil sampling. It is undoubtedly true 
that the laws governing capillary distribution of soil moisture as de- 
termined in small columns would also govern in the field, hence the 
size of the column is not material. 
THE PRINCIPAL RESULTS OF THE EXPERIMENTS. 
The experiments disclosed a number of very interesting and im- 
portant facts with regard to the distribution of soil moisture im the 
soils tested. 
The maximum percentage was found, not immediately above the 
water surface, but at an appreciable distance above it. 
The capillary moisture was not distributed at a rate uniformly de- 
creasing with the distance above the water table, but irregularly. 
In most cases the maximum percentage of moisture to be found in 
the wetted area of the soil above the water table was several inches 
above the surface of the water. The average percentage of moisture 
contained in this wetted area above the water table was found at 
about three-fifths of the height in most cases. In a majority of the 
soils used in these experiments the lower half of the wetted area above 
the water table contained too much moisture for the best growth of 
most plants. These tests show that in the presence of a water table, 
plant roots need not go to the water table itself for moisture. 
In a loam or heavier soil, a shallow drain, say 2 or 3 feet below the 
surface, either open or closed, would in the presence of a water table 
remove but little water from the soil above the drain. In case of 
under drainage, where the water table remains at the level of the 
drains, there is a large amount of moisture held by the soil above the 
drains not subject to drainage. 
The distribution of soil moisture in a horizontal direction in the 
field depends very largely upon the possibility of vertical movement 
either upward or downward. If there are rather impervious strata 
both above and below a stratum of soils such as those used in these 
tests, then the lateral distribution will be somewhat uniform over 
the entire wetted area, with a tendency to decrease gradually with 
distance from the source of water. 
If these semi-impervious or impervious strata incline downward at 
15 degrees or more from the horizontal, then the intervening stratum 
will have a moisture distribution differing from either the vertical or 
