30 BULLETIN 1173, U. S. DEPARTMENT OF AGRICULTURE. 
TABLE 15.—Annual and average yields of wheat in the depth-of-plowing experiments at 
Moro, Oreg., in the years 1912 and 1914 to 1921, inclusive. 
[Pacific Bluestem spring wheat was grown in 1912 and from 1914 to 1917, inclusive; Early Baart spring 
wheat in 1918 and 1919; and Turkey winter wheat in 1920 and 1921.} 
Annual and average yields per acre (bushels). 
Cultivation method. Plat. | 
| | 9-year 
1912 1914 | 1915 | 1916 | 1917 | 1918 1919 | 1920 | 1921 aver- 
| | | j | age. 
: | Can (hess b (ee er ede | | | 
No.1...| 13.6 | 14.6 | 13.6 | 28.7 | 16.0 | 14.2 | 22.6 | 23.3] 31.2] 19.8 
||No. 2... 13.6 | 13.9 | 16.8 | 26.7 | 182 | 13.2 | 20.1] 187|35.5| 196° 
No.4... 14.5 13.9 17.5 | 26.0 8.8 12.7 | 23.5 | 18.7 | 38.5) 19.5 
; No.5...| 15.0 | 13.5 | 17.5 | 28.3 | 20.3 | 12.0 | 20.5 | 21.3 | 37.3) 20.6 
Shallow spring plowing. ....---)No,6:_.| 12.9 | 15.5 | 17.0 | 28.5 | 183 | 14.3 | 21.6 | 21.8 | 37.5| 20.8 
No.7...| 16.6 |17.3| 9.6 | 31.7| 87 | 14.2 | 25.1] 185 | 36.7] 19.8 
}No.9...| 15.1 | 14.5 | 16.6 | 32.2} 16.7 | 12.5 | 21.6 | 26.2 | 35.5! 21.2 
No. 10... 18.0 | 17.0 | 16.3 | 33.0 | 19.0 | 13.5 | 21.2 | 27.3] 343) 22.2 
| | — ee 
VETOED vox oe sec = See aso |ceeeee es | 14.9 | 15.0 | 15.6 | 29.4 | 15.9 | 13.3 | 22.0 | 22.0 | 35.8) 20.4 
No.1...| 12.8] 9.0 | 14.8 | 27.2] 19.3| 9.5 |20.8| 148/365! 183 
No.2... 14.4 | 8.0] 17.5 | 25.0] 19.7 | 10.2 | 22.5| 18.71} 45.5) 20.2 
No.4... 15.3 | 12.0 | 19.0 | 30.0 | 18.2 | 12.2 | 20.8 | 22.8|347/ 206 
i, 0.5...| 13.9 | 14.0 | 16.3 | 31.0 | 182 | 13.0 | 20.8 | 26.2 | 33.0! 20.7 
Deep spring plowing.........-. No.6...| 13.4 | 14.3 | 17.0 | 30.3 | 20.0 | 15.5 | 20.2 | 27.1 | 36.5| 21.6 
No.7...| 16.1 | 15.5 | 16.8 | $2.5 | 17.0 | 14.7| 185 | 20.0 | 34.71 20.6 
No.9...| 18.0 | 17.1 | 16.6 | 36.7 | 18.3 | 15.0 | 21.8 | 32.3 | 37.2 | 23.7 
No. 10..) 17.8 | 16.3 | 16.1 | 36.3 | 22.0 | 17.0 | 23.3 | 34.5 | 40.8] 249 
OTE Ree a eget 15.2 | 13.3 | 16.8 31.1 | 19.1 | 13.4 | 21.1 | 24.5 | 37.4] 21.3 
No.3...) 13.3 | 13.0] 16.0 | 28.2 | 17.3 | 13.2 | 24.7 | 20.5 | 39.0] 20.6 
Checks, shallow series. ........ (No. 13.0 | 16.5 | 181 323 | 15.6 15.2 | 225/287 40.7) 225 
0.3...| 15.0 | 12.0 | 15.3 | 27.8 | 19.3 | 10.5 | 20.0| 19.0 | 42.0} 20.1 
Checks, deep series. ........... {No.8.. | 15.6 | 16.5 | 15.8 | 36.8.| 17.0 | 14.0 | 22.8 | 31.5 | 37.5| 23.1 
LE see RE ES REN ie pet da sea on eee... Rea (esas saute ee Se ere 21.6 
1 
RESULTS AT LIND. 
The depth-of-plowing experiments at Lind include variations in 
depth on all dates of fall plowing and spring plowing. Fall plowi 
of fallow is not generally practiced in the Columbia Basin, an 
therefore but two depths are used on the fall dates, as compared 
with three on each of the spring dates. These are more extensive 
experiments than those concerned with dates of plowing, and 26 
plats were used exclusively for this purpose, 13 being in crop and 
13 in fallow each year. The results are presented in Table 16 and 
in part are shown graphically in Figure 16. 
Dry fall disking retards the absorption of soil moisture. From 
the data on comparative yield it is apparent, with the limited mois- 
ture supply and the soil type prevailing at Lind, that the fall plow- 
ing must have the same effect. It is further apparent that the 
detrimental effect must be greater as the depth of the layer of loose 
soil is increased, the more shallow plowing giving the best return in 
yield. It is logical to assume, therefore, that any tillage given to 
soil in a dry condition should be as shallow as possible. 
The three spring and summer dates represent plowing under three 
different conditions of soil moisture and subsequent precipitation. 
The first represents plowing in a very moist soil with more or less 
subsequent rainfall; the second, plowing in a somewhat drier surface 
soil with less succeeding 
fo) 
rainfall; and the third, 
with practically no subsequent rainfall. 
plowing in 
dry soil 
