4 BULLETIN 1309, U. S. DEPARTMENT OF AGRICULTURE 
year average. Both the 1917 and 1921 crops were grown on the same 
portion of the farm and under as similar cultural treatment as pos- 
sible. The spring stands were slightly better in 1921 than in 1917. 
The rainfall during April, May, and June. 1917, was low, the total 
being 2 inches less than the 12-year average for those months, 
whereas that for the same months 'in 1921 was slightly over 2 inches 
more than the 12-year average- 
Figure 1 shows' graphically the annual average yields of the 17 
varieties of winter wheat grown continuously during the period in 
which weather data have been recorded at the farm and the total 
April, May, and June rainfall for each year of the 12-year period from 
1912 to 1923, inclusive, the precipitation curve being inverted. The 
number of factors involved in determining yield as well as the short 
period covered by the graph allow no definite conclusions. It appears, 
however, that heavy total precipitation during the season of active 
growth in spring has not resulted in high wheat yields. The three 
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Fig. 1.— Diagram showing the annual average yields of 17 varieties of winter wheat grown at the Arling- 
ton Experiment Farm continuously during the 12-year period, 1912-1923, inclusive, and the total April, 
May, and June rainfall for each year 
poorest wheat years — 1913, 1916, and 1921 — are those in which the 
precipitation totals are highest. High yields, however, have not fol- 
lowed exactly the inverted rainfall curve, though in the years of less 
than average rainfall better than average yields have been produced. 
The fertile moisture-retentive soil produces a rank, vigorous 
growth of wheat and large yields of straw. Under unfavorable con- 
ditions, such as heavy rains about heading time, lodging is severe 
and often materially reduces wheat yields, the reduction depending 
somewhat on the degree of lodging and the stage of development at 
which it occurs. In 1922, head samples selected from a portion of a 
plat which had lodged when the plants were fully headed were com- 
pared with head samples from a near-by unlodged section of the same 
plat, notes being taken on the percentage of seed set and the weight 
of kernels. The data obtained (Table 2) are believed to be typical 
of the injury done by early lodging to the quantity and quality of the 
grain produced. Further loss occurs in harvesting lodged plats. 
Damage also may occur in the shock if the weather is unfavorable, 
as it is difficult to build good shocks with tangled bundles of lodged 
