RELATION OF YIELD TO RAINFALL IN THE GREAT PLAINS. 29 



In 1909, on the other hand, the highest yield of wheat at North 

 Platte was obtained from spring-plowed land. The seasonal rain- 

 fall was the highest of any of the three years. But the rainfall was 

 not the factor which controlled the yields during this season. There 

 was abundant moisture for all the crops. In this case the tempera- 

 ture was the controlling factor. The wheat sown on the conserva- 

 tion plats encountered freezing weather for five days just as it was 

 coming up. In the spring-plowed plats, where conditions were not 

 so favorable, the germination was retarded and the plants were not 

 injured during this cold weather. More freezing weather occurred a 

 week later, which injured the more advanced grain to such an extent 

 that it never recovered, and the wheat sown on spring-plowed land 

 consequently gave better yields. 



The stations so far considered are located in the central and 

 northern part of the Great Plains, where the conditions are not so 

 severe owing to the lower evaporation. The remaining stations are 

 located in a section subject to high winds, hail, and high evaporation. 



At Akron, Colo., in 1909 the spring was cold and wet. Under these 

 conditions we would not expect marked differences between spring- 

 plowing and summer-tillage methods. The average yield at the sta- 

 tion was about 16 bushels, with a seasonal rainfall of 10 inches. 



At Hays, Kans., in 1908 the average yield was only about 4 bushels 

 with a seasonal rainfall of 14 inches. This low yield was due to high 

 winds and dry weather in the spring months. The crop in 1909 was 

 destroyed by hail. 



At Garden City, Kans., in 1909 the average yield of wheat was 3 

 bushels per acre, with a seasonal rainfall of 11 inches. There was 2 

 inches of precipitation in March, which provided sufficient moisture 

 for the germination of the wheat, but there was practically no pre- 

 cipitation during April and the first half of May, which so weakened 

 the crop that the later rains could not be utilized. 



The crop at Dalhart, Tex., in 1908 was destroyed by drought. In 

 1909 the spring was very dry, less than 3 inches of water falling from 

 September 1 to May 1 . Wheat grown on summer-tilled land was the 

 only plat that was able to withstand this weather. A hailstorm on 

 June 19 completed the destruction of those crops that had been weak- 

 ened by the drought, and injured the wheat on the summer-tilled 

 plat, which, however, gave a yield of 10.5 bushels per acre, with a 

 seasonal rainfall of only 8 inches. 



Spring wheat at Amarillo, Tex., during the season of 1907 was a 

 failure, owing to the extremely dry weather of the spring and early 

 summer, combined with the severe hailstorm of June 3. The aver- 

 age yield was only about 2 bushels per acre. In 1908 an average 

 yield of about 12 bushels was obtained on a seasonal rainfall of 12.6 

 inches. March was very dry during this season, but good rains were 



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