The Storage and Use of Soil Moisture 
67 
able water to that depth and did not use any appreciable amount 
from below four feet. 
Chart IX shows again the use of the available water by the 
crop. In each case the land was summer tilled the previous year, 
and the crop used was spring wheat. In 1911 the first sampling 
does not show the usual amount of available water. As- pre- 
viously shown^ summer tilling in 1910 did not accumulate much 
water. June 23, the last sampling, shows some available water- 
in the third and fourth feet. At this date the growth was still 
sustaining itself, and showed evidence of making a crop. Grass- 
hoppers, however, destroyed the crop soon after this date and 
the sampling was neglected. A sampling made early in Sep- 
tember showed no available water in the fourth foot. 
The 1912 chart shows an increase of available water during 
April and May. It also shows the use of the water from the 
soil earlier in the season than was shown for either year given 
in Chart VIII. A comparison of the distribution of the rainfall 
for these years will account for this. The crop was seeded April 
12. harvested July 25, and yielded 10.5 bushels an acre. 
Charts X to XV are offered to show the effect on the moisture 
content of the soil of continuous cropping to small grain. 
The same general explanation that was given for Chart III 
will answer for Charts X to XV inclusive. The curves shown in 
these charts represent the moisture content for each foot-section 
of soil to a depth of six feet. All rains of one-tenth inch or more 
are shown in the division for precipitation. The seeding and 
harvest dates are marked on each chart, except 1911. when there 
was no harvest. The yields are shown for each year. Each chart 
represents the moisture content of the same plat for the year 
shown thru the six consecutive years. This plat has grown the 
same crop, spring wheat, and received much the same tillage each 
year. It is fall plowed and harrowed as soon as practical after 
harvest. 
In the spring of 1907 the soil was practically filled with water 
to a depth of three feet. This was as deep as the sampling was 
done. The first sampling after harvest shows the soil dry to four 
feet. 
The first sampling in 1908, as shown in Chart XI, shows 
available water in the first two feet of soil. This had been re- 
tained from rain or snow during the winter. The first and 
second feet were completely filled by the heavy rains in May. 
June shows a very heavy rainfall and some water passed into 
the third foot. Below this there was practically no change in 
