32 BULLETIN 1173, U. S. DEPARTMENT OF AGRICULTURE. 
TaBLe 17.—Annual and average yields of Turkey winter wheat grown in tenth-acre plats 
in the depth-of-plowing experiments at Nephi, Utah, during the 12-year period from 
1910 to 1921, rnelusive. 
Annual and average yields per acre (bushels).! 
Average. 
Treatment. ‘ 
} | 5 | 
1910 | 1911 | 1912 | 1913 | 1914 | 1916 | 1917 | 1918 | 1919 | 1920 | 1921 | 1910 1916 
} | | 
to 
1921 | 1921 
Subsoiled 18 inches | | | | | | | 
ee | 14.0 | 28.0/ 180] 4.0 | 386 | 16.2 | 27.7 | 16.5 | 19.0 | 26.8 | 44.2 | 23.0} 25.1 
ith ee ee | 13.0 | 29.0 | 19.0} ‘650 | 41.3 | 15.8 | 2752'} 20.3 | 23.7 | 24.5'| 43.4 |) 23595 pean 
Plowed 10 inches | 
BEAU oot ote ene === | 13.0 | 29.0 | 21.0 | 7.0 | 38.8 | 15.7 | 28.2 | 17.3 | 25.5 | 
Plowed 5inches deep.| 12.0 | 27.0 | 20.0 | 10.0 | 39.5 | 13.3 | 28.5; 18.7 | 23.8 | 
Plowed 8 inches in | 
fall and 3 inches in | 
| 
ee 
SEINE Soe cee fl aac ooo bee ee pat —ce Boake 16.5 | 26.2] 182 | 17.3 |32,.0°| 41.17) 2 | 25.2 @ 
Plowed 3 inches in | | - = 
fall and 8 inches in | | 
Ei fe ae ey eT 5 Deedes ies 14.5. 728.2 | 1423 | 155528. 0.1 387 ee |- 23.2 2 
Plowed 8 inches in | | 
both fallandspring.|...... ee eee Sele eee sl oe eee 15.7 | 26:8: P1523 | ATO STS: Sk ee eee | 23.5 
| 
1 No yields reported for 1915. 3 
From the results in Table 17 it is evident that plowing beyond a ~ 
depth of 10 inches is not necessary. In fact, when the labor costs _ 
of subsoiling are considered, this practice is decidedly unprofitable 
under conditions similar to those at Nephi. Between the 5-inch 
and 10-inch plowings there was an average difference of 1.4 bushels in 
favor of the greater depth for the period from 1910 to 1921 and an 
average difference of 2.5 bushels from 1916 to 1921. This indicates 
that fall plowing should be deeper than 5 inches. 
In the second part of Table 17 the 8-inch fall plowing followed by 
plowing 3 inches deep the following spring gave a higher acre yield 
than either one of the two other methods. Taking all of the data 
presented in Table 17 into consideration, as well as other data given — 
in this bulletin, it can be safely stated that one plowing either in ~ 
fall or spring is sufficient if weeds can be controlled. i 
CULTIVATION OF SUMMER FALLOW. 
PACKING AFTER PLOWING. 
The use of surface and subsurface packers has been quite widely 
advocated, with the idea that they aid in conserving moisture and 
in increasing wheat yields. At present these implements are used 
by dry farmers in the West only to a limited extent. 
Experiments to determine the effect of packing the soil on the 
yield of wheat grown after fallow have been conducted at Moro, 
Oreg., and at Lind, Wash. At Moro both the subsurface and the 
surface packer were used (Table 10) on land plowed April 1, May 1, 
and June 1 on which Turkey winter wheat was grown, and on early, 
deep and shallow spring plowing on which spring wheat was grown. 
At Lind the subsurface packer was used on ground plowed in March, 
April, and June. 
Ce ee ee ee ee er eae eee ne 
