10 
BULLETIN 546, IT. S. DEPAKTMENT OF AGRICULTURE. 
Except for a very slightly lower average moisture content in the 
first foot of the fall-irrigated plats sampled May 24, the moisture 
determinations made in 1915 disclosed no differences large enough to 
be considered significant between the fall-irrigated plats and the 
checks. As in the spring of 1914, the soil on all the plats sampled con- 
tained an abundant supply of moisture. As the moisture content of 
all the plats before the first irrigation was found to be substantially 
the same, no further moisture determinations were made during the 
season. 
Soil moisture in 1916. — The first irrigation in 1916 was applied 
July 6. Soil-moisture determinations were made to a depth of 2 feet 
on all the plats in oats, wheat, and barley on June 10, and the plats in 
potatoes, beets, corn, and flax were sampled to the same depth on 
June 30. The results of the two samplings are summarized in Table 
VIII, which also shows the probable errors of the averages of mois- 
ture content. 
Table VIII. — Summary of the results of soil-moisture determinations made in 1916 in 
the fall-irrigation experiments at the Belle Fourche Experiment Farm. 
Depth. 
Fall-irrigated plats. 
Cheek plats. 
Date. 
Num- 
ber of 
plats 
aver- 
aged. 
Moisture 
content. 
Num- 
ber of 
plats 
aver- 
aged. 
Moisture 
content. 
Difference 
in favor 
of fall 
irrigation. 
June 10 
Feet. 
1 
2 
1 
2 
Per cent. 
6l 27.7±0.6 
6 ' 29. 2± . 8 
8 29. 7± .6 
8 30.2+ .3 
6 
6 
8 
8 
Per cent. 
27.4±1.0 
29. 2± .9 
29.9±1.2 
30. 1± .4 
Per cent. 
+0. 3±1. 2 
Do . 
±1.2 
June 30 
- .2 + 1.3 
Do 
+ .1± .5 
The results of the soil-moisture determinations made in 1916 were 
practically the same as those secured in 1915. The soil on all the 
plats contained an abundance of moisture at the time of sampling, 
and there was no significant difference between the moisture content 
of the fall-irrigated plats and that of the checks. 
The results of the determinations made during the three years may 
be summarized by the statement that any higher soil-moisture con- 
tent resulting from fall irrigation was found only at times when the 
soil on both the fall-irrigated plats and the check plats was well sup- 
plied with water and that all significant differences in soil moisture 
disappeared early in the growing season, so that the crops showed no 
effects of fall irrigation. 
CHARACTER OF SOIL THE DETERMINING FACTOR. 
The fact that fall irrigation produced no effect on crop yields at 
Belle Fourche while it resulted in decidedly higher yields at Scotts- 
bluff makes it desirable to compare the rainfall and the soil con- 
ditions at the two places. The comparison is shown in Table IX. 
