16 BULLETIN 1173, U. S. DEPARTMENT OF AGRICULTURE. , 
Because of the comparatively short period for which data are 
available, no conclusions can be safely drawn from the results shown 
in Table 8. Of the five methods included in this experiment burning 
all of the straw produced slightly the highest average yields in the 
6-year period. ! 
The deficiency of humus in the dry-farm soils of the Columbia 
River and Great Basin regions suggests the advisability of turning 
/H13 19/4 1905 1916 1077 1918 1919 1920 192/ 
40 
IS 
Tie 
AVERAGE - = 7 pe 
@| see ia Re 
IPAING DLSHED ———_—_—_—£ 
NOT DISHED --------- 
Fig. 12.—Annual and average acre yields, in bushels, of winter wheat in varying numbers of years at Moro, 
Oreg., and Lind, Wash., when grown after summer fallow for which the ground had been plowed in late 
spring with the stubble disked or not disked in early spring before plowing. 
* 
under the stubble and straw in preference to burning them. Stubble 
and straw decay very slowly in these soils, however, and when turned 
under in too large quantities occasionally may produce an unfavorable 
soil condition by inducing excessive drying or by producing an 
incorrect balance between the nitrates and moisture supply, thereby 
causing a rank growth of straw, which may induce drought injury 
and reduce grain yields. 
-ialeniiliiecadsan. | 
