22 BULLETIN 1094, U. S. DEPARTMENT OF AGRICULTURE. 
thin stand and winterkilling, and five sown in disked stubble averaged 
3.9 bushels per acre. In 1918 three plowed plats averaged 15.8 bushels 
and three not plowed 24.7 bushels. In 1919 three plowed plats © 
averaged 19 bushels and three unplowed 22.2 bushels. In 1920 four — 
plowed plats averaged 22.6 bushels and two unplowed 25.8 bushels. — 
In four years the total gain from not plowing was 19.2 bushels, an — 
average gain of 4.8 bushels per year. In this group of plats, as in © 
‘rotation No. 591, which has not been plowed since 1912, there is no 
evidence of deterioration from the continued omission of plowing. 
TABLE 9.— Yields of wheat on plats continuously cropped to wheat but plowed at different 
intervals at the Fort Hays branch station for the 5-year period from 1916 to 
1920, inclusive. } 
[Yields following plowing shown by boldface type.] 
| Yields per acre (bushels). 
Average 
Year. Increase 
on un- 
Plat A.} Plat B.| Plat C.| Plat D.| Plat E.| Plat F. oes Un- | plowed 
late plowed} plats 
ee plats. 
AOLG Ree ae ee ee , 33-8 39.8 35.2 37.4 35.9 SSIS) Eee oe es | bie CERERT 
HOW 259: a8 fe EE Sheet 0 2.6 3.8 4.9 2.8 5.6 t) 3.9 3.9 
Ut) fhe Sees eee | 10.8 16.0 23.8 26.3 24.0 20.5 15.8 24.7 8.9 
1G 22 ee 2 8 ae ees oo 15.8 20.5 21.8 22.3 23.8 19.5 19.0 22.2 3.2 
TET, ie yee BO a 2S ey oe een V5 aie 2tes 23.4 29.8 28.5 22.6 25.8 a2 
Average, 1917 to 1920..| 11.0 | 15.1 | 17.8 19.2 | 20.1 18.5 | 14.4 19.2 4.8 
Near these plats in the field are two other rotations that were 
started in time to be productive of evidence on the same subject 
in 1919 and 1920. Rotation No. 568 is fallow, winter wheat on 
fallow, and winter wheat sown in stubble. Rotation No. 580 is the 
same thing lengthened one year by early plowing the last wheat 
stubble and raising a third crop of wheat before fallowing. In 1919 
the stubbled crop was heavier than either that fallowed or plowed. 
In 1920 the fallowed was heavier than the stubbled, and the stubbled 
heavier than the plowed. As has been noted before, 1919 was dis- 
tinctly unfavorable to methods that prompted a rank growth. In 
1920 there was a similar tendency, but it did not go far enough to 
overcome entirely the initial advantage enjoyed by such methods 
as fallow.’ 
The somewhat anomalous condition is presented of early plowing 
or cultivation yielding heavier than late plowing, but no cultivation 
at all sometimes yielding heavier than either and averaging nearly 
as much as the best methods of early cultivation. The first is suscep- 
8 In 1921 the yield of the continuously stubbled plat known as rotation No. 591 fell to about one-half 
that of early plowing, but was still above that of late plowing. In the other experiments described, wheat 
sown in disked stubble on which plowing had been deferred for a lesser number of years maintained yields 
as high as on early plowing, or even higher. 
