26 BULLETIN 1173, U. S. DEPARTMENT OF AGRICULTURE. 
The variations in yield for the different dates of plowing given in 
Table 12 are not large and perhaps are too small to serve as a basis _ 
for conclusions. The percentage variations, however, are comparable 
with those found under the more favorable conditions at the other 
two stations, results from which are reported in this bulletin. These 
data show what may be expected where moisture is an extreme limit- 
ing factor in production. 
The time and method of tillage are determined by local conditions, 
and in the drier portions of the Columbia Basin fall plowing, either 
wet or dry, is not good practice. The data given in Table 12 are in 
full agreement with farm experience in this respect. 
Of the experiments in spring plowing, the results from the first 
two dates are practically identical, the yields being higher than 
those obtained from the late or summer plowing. During the spring, 
before volunteer grain and weeds grow freely, there is no advantage 
irom a moisture standpoint in stirrmg the soil. Moisture studies 
show that before this time, which during the period of these exper- 
iments corresponded approximately to the date of the et plowing, 
nothing was gained in moisture content by plowing and that moisture 
content was equal in the plats plowed in March and April. Therefore 
the yields are equal. After this time the drain on soil moisture from 
plant growth becomes heavy enough, unless checked by tillage, to 
reduce materially the total moisture in the soil, and the yields from 
the plats plowed in June consequently are lower. 
RESULTS AT NEPHI. 
Date-of-plowing experiments were conducted at Nephi during the 
6-year period, 1916 to 1921, inclusive. 
The time that spring plowing can be started on the dry farms near 
Nephi is rather indefinite, because of the variability of the seasons. 
This operation can begin as early as April 1 in some years, but in 
others not until May 1, and occasionally it is delayed still later. 
Because of this fact, no definite dates were set for plowing the various 
plats, but different stages of growth of volunteer wheat were used in- 
stead. The first plowing is done just as soon as the plow will scour; the 
second, when the volunteer growth is 6 inches high; the third, when 
the wheat is 12 inches high; the fourth, when the volunteer crop is 
in early bloom; and the fifth, when the wheat kernel is in the milk 
stage. Jor fall plowing the land is turned over at a medium early 
date, near October 10. The depth of plowing usually is 8 inches. 
he experiments were conducted on duplicate tenth-acre plats 36 
by 121 feet. The results are shown in Table 13 and graphically in 
Figures 14 and 15. 
The results shown in Table 13 indicate a very decided advantage 
in favor of early spring plowing as compared with plowing at later — 
dates. The yield decreases regularly with the later plowing. The — 
difference between fall plowing and spring plowing in this test was 
very slightly in favor aft fall plowing. 
A large part of the plowing on the dry lands in the Great Basin 
is left until spring. Spring plowing in this section usually is cheaper 
than fall plowing, because less power is needed for the operation and 
because spring-plowed land does not require so much summer culti- 
vation to check the growth of weeds and volunteer wheat. 
