BROOM-CORN EXPERIMENTS AT WOODWARD, OKLAHOMA. 9 
for the entire day. Such high winds may cause great damage 
either by covering up the young plants, by cutting them off with 
moving particles of soil, or by blowing down the crop when it is 
approaching maturity. 
Temperature. 
The daily range in temperature is large. In summer the days are 
warm to hot, but the nights usually are cool. The data on mean, 
maximum, and minimum temperatures and the dates, by months, foe 
the season (April to September ) in the 5-year period from 1914 to 
1918, inclusive, are given in Table III, which also contains data on 
- wind movement. 
The temperature in winter seldom reaches zero, but occasionally 
even lower temperatures occur. In summer the temperature reaches 
the 100° F. mark and above quite frequently. The maximum 
temperature in this 5-year period, 109° F., was recorded on several 
dates in June, 1917. The average date of the last spring frost is 
April 11, and that of the first fall frost, October 25, leaving an 
average ‘hose free period of 196 days. 
Evaporation. 
In the district here described the loss of moisture by evaporation 
is very, great. The chief factors that influence evaporation are pre- 
cipitation, wind, and temperature. The maximum evaporation 
naturally occurs in periods of high temperatures, low rainfall, and 
strong winds. | 
TABLE [V.—Monthly seasonal and average monthly precipitation and evapora- 
tion at the Woodward (Okla.) Field Station during the six months from April 
to September, inclusive, in the 5-year period from 1914 to 1918, inclusive. 
{Data (in inches) furnished by the Offic? of Biovhysizal Investigations, Bureau of Plant Industry.) 
April. May. June. July. August. | September. Total. 
WCRI, Pre- Pre- Pre- Sl eleai vee |e @xa| aes na elere- Dol) Veakeed he 
cipi Eved- SEN yap cipi- war") cipi- EMap cipi Eyep cipi- yvap ODE Fvep 
las a- aas|s deine aaa lps a- aan 
ene tion. tion. Gea ion tion. Se tion. HOT tion. rie tion. HGH tion 
TO AGS oe er 1.7 6.8 3.2 6.2 0.6 | 11.3 1.9} 10.9 2.6 8.9 0.6 8.4 | 10.5 52.6 
LOSS Apa ee 6.5 6.0 5.3 1 6.7 2.4 6.6 3.1 | 10.0 3.6 6.5 5.7 5.8 | 26.8 41.7 
NOL G Reena eo a3) 6.0 1.7 9.8 | 10.3 Het 0 10. 4 1.0} 11.2 ys 3 7.5 | 17.6 52.6 
ICN hy ees ices 16 ee, 1.0 7.0 1.4] 11.3 idle Eablet 6.9 7.4 2.0 5.0 | 14.0 49.6 
GUS es oe 222 5.0 4.0 9.3 1.9 8.7 -7 | 10.1 1.3 | 11.0 1.2 5.8] 11.3 49.9 
Average. Done Gaile 3-0 Wamu Seale Otale Tea|10:6 \o13 ule SO peoe4 |) 6. o8| 16.08) 4053 
Table IV contains a comparison of the monthly precipitation and 
evaporation records made at the Woodward Field Station during 
the six months from April to September in each year of the 5-year 
period from 1914 to 1918, inclusive. The evaporation measured is 
147841°—20—Bull. 886-——2 
