8 BULLETIN 1287, U. S. DEPARTMENT OF AGRICULTURE 
of grain. Figure 3 shows graphically the annual and seasonal pre- 
cipitation at Akron for the 15 years from 1908 to 1922, inclusive. 
The limiting factor in crop production at Akron is nearly always the 
moisture supply, although winter grains have been injured by low 
temperatures and hail sometimes causes severe crop losses. The 
yields of spring grains, however, are determined largely by the amount 
and distribution of the seasonal precipitation. In some seasons, as 
that of 1918, the rains came too late to benefit the cereals. In several 
other seasons the lack of moisture during the heading and ripening 
period caused low yields. 
Rains of less than one-fourth inch during the growing season unless 
followed or preceded by other rains within 24 hours are of almost no 
value to grain crops in this section. In 1921 but 9.15 inches of pre- 
cipitation were recorded during the growing season. There was prac- 
tically no rainfall heavy enough to be of value to crops from April 15 
until after the crops were harvested in July. 
N 
S 
ACHE YIELD IN BUSHELS 
YSUNE FRECIPITATION /N INCHES 
JUNE PRECIPITATION IN INCHES 
—-——- —- ACRE VIELD (NW BUSHELS. OF KHARKOF HE: 5 
----~------ AGRE YIELD /W BUSHELS OF PELISSTL RNG 
(206 VEL SLO. VTEDU ELER EVEL ELE EVE EY SVE MES EYE EP ELE! 7 
Fic. 4——Graphs showing June precipitation and acre yields of Kharkof and Peliss wheats at the Akron 
Field Station during the 15-year period, 1908-1922, inclusive 
Figure 4 shows graphically the relation of the June precipitation to 
the yields of Kharkof winter wheat (C. I. No. 1583) and Peliss durum 
spring wheat (C. I. No. 1584). Table 2 gives these data in tabular 
form. In 1909 no winter wheat was grown, and in 1920 the stand of 
winter wheat was poor, owing to soil blowing and winterkilling. In 
the fall of 1918 no winter-wheat varieties were sown in plats, and the 
yield given for 1919 in Table 2 is the average of two increase plats of 
Kharkof, one sown on cornland and one on fallow. The acer 
(fig. 4) shows that a marked relation exists between June precipitation 
and crop yields. In nearly every case a heavy June precipitation is 
followed by a good yield of wheat, whereas a low precipitation in June 
has resulted in a lowering of the wheat yield. 
EVAPORATION 
The seasonal evaporation at Akron is closely related to the seasonal 
precipitation, and among the factors which influence crop growth it 
possibly ranks second. The daily evaporation has been recorded at 
the station during the growing months since the station was estab- 
— ee! 
