U. S. DEPARTMENT OE AGRICULTURE 



The highest precipitation was 30.41 inches in 1915; the lowest was 

 9.24 inches in 1931. In only one year, 1915, was the moisture supply 

 sufficient to mature all crops without drought damage. In several 

 other years the damage was small, but in the majority of years yields 

 were sharply reduced by drought, and in a number near failure re- 

 sulted from severe drought. The normal expectation is for drought 

 injury at some time during the growing season. 



The fact that the average precipitation is 15.90 inches does not 

 mean that this is the most probable amount. In 13 out of 21 years 

 the rainfall was below the average. In other words, the normal ex- 

 pectation is for a less-than-average precipitation approximately 60 

 percent of the time. 



Hail played an important part in determining crop yields. Hail- 

 storms are frequent, but the injured areas are not usually large, and 

 it is likely that the 15-percent average hail damage at the station is 

 not far from the average for the section as a whole. At any rate, the 

 probability of hail damage is a factor that must be taken into con- 

 sideration in farming operations in this section. 



The average evaporation for the 6 summer months April-Septem- 

 ber, was 38.206 inches during the 20 years, that observations were 

 taken. The highest evaporation was 51.760 inches in 1931, the year 

 with the lowest precipitation. The lowest evaporation was 28.908 

 inches in 1915, the year with the highest precipitation. In general, 

 low precipitation is associated with high evaporation, and high pre- 

 cipitation with low evaporation. 



The temperature at Ardmore is characteristic of the northern Great 

 Plains. Extremes of temperature are reached, both in summer and 

 in winter. The lowest temperature recorded at the field station was 

 -34° F. on January 17, 1916. The highest was 109° on July 25, 

 1931. In most winters temperatures of —20° or lower are recorded, 

 but the minimum temperature reached —30° only seven times in 

 20 years. Temperatures of 100° are reached nearly every year, but 

 temperatures of 105° or more were recorded on only 13 days in 20 

 years. Eight of these days were in the exceedingly hot and dry year 

 of 1931. 



In the 21-year period, 1912-32, the average date of the last killing 

 frost in spring was May 10 and of the first in autumn September 

 27. The average frost-free period was 140 days. Frost-free periods 

 in individual years ranged from 120 days in 1916 to 179 days in 

 1930. 



FIELD CROP INVESTIGATIONS 



Crop investigations at Ardmore were divided into three principal 

 lines: (1) The production of crops in rotation plots for the purpose 

 of determining the sequences and cultural methods under which the 

 staple crops of the section should be grown; (2) growth of crops on 

 a field scale as a feed-producing enterprise; and (3) tests of varieties 

 of grain and forage crops. These three lines of endeavor will be 

 discussed separately. 



CROP ROTATIONS AND CULTURAL METHODS 



The crop rotations comprise a study of the effects of different 

 cultural methods and sequences on the yields of crops. They also 



