sept 9.1918 Variations in Moisture Content of a Loess Soil 471 
Thus the highest ratios found in the fallow and grass fields soon after 
heavy rains were 3.6 to 4.0 in the uppermost 6 inches and 2.9 to 3.3 in the 
second 6 inches, and under the influence of percolation alone these fell 
gradually to 2.5 to 3.0 in the lower half-foot and to a slightly higher 
minimum in the upper 6-inch section. In the exposed subsoil there was 
no difference to be observed between the upper and lower halves of the 
foot section, both showing a ratio of 2.3 to 2.5 soon after heavy rains, and 
this gradually falling to 2.1 or 2.2. 
lower limit 
Marked differences, owing to the withdrawal of water through the 
roots in the grass and corn fields, developed during periods of dry weather, 
and continued even after moderate rains. 
In the fallow loss of moisture could occur only through evaporation 
from the surface or percolation ipto the subsoil, with the result that 
there was a much greater loss from the levels near the surface. The 
extreme condition was shown on May 25, when the ratio in the surface 
inch fell to 0.5 and in the second inch to 1.1, while in the fourth it was 
still 2.6. The same limited depth of drying was shown during the dry 
periods preceding the samplings of July 10 and August 30. The per¬ 
sistent moistness throughout the greater portion of the surface foot in the 
fallow may be well brought out by considering the second 6-inch section 
as a whole. The ratio in this did not fall below 2.6 at any time during 
the five months included in the study, and on only three occasions, May 
25, August 28 and 30, was it found this low. The ratio for this 6-inch 
section varied only between the limits of 2.6 and 3.1, except immedi¬ 
ately after the very heavy rain of June 12-13. Even in the surface 
layers the ratio was in general well above that corresponding to the 
wilting coefficient (1.5), in the fourth inch on no occasion falling below 
1.8, and in the third inch being found below 1.6 only once, on June 1. 
Even in the second inch it was below 2.0 for only very short periods. 
There appears no reason to suspect that during the part of the year 
not included in the study we could have found drier soil in any of the 
levels than we encountered in the course of the work, which embraced 
the greater part of the growing season. From this it is evident that at 
Lincoln in fields kept in clean cultivation only rarely does the second 
inch of soil become too dry to permit the germination of seeds and the 
satisfactory growth of roots, while the fourth inch appears to remain 
sufficiently moist for these purposes throughout even exceptionally 
severe drouths. 
The conditions in the cornfield were found intermediate between those 
in the fallow and those in the grass fields. Between June 14 and August 1 
no samplings were made among the corn plants. After the plants had 
become large enough to make an appreciable draft upon the soil moisture, 
