CLIMATIC RELATIONS 



267 



the same crop. The measure employed in the experi- 

 ments is the ratio of the weight of water absorbed 

 during growth to the weight of dry matter produced. 

 This ratio is surprisingly low in corn, being 239 in the 

 Esperanza variety. 



The Kursk millet, introduced by the author from 

 Kursk Government, Russia, showed the smallest water 

 requirement, 187, so far recorded for any crop. In the 

 experiments of 1910-11, Kubanka wheat was the most 

 efficient of all varieties of wheat, oats, barley, rye, and 

 rice. In 1912-13, Turkey and Kharkov wheats were 

 first used in the experiments and gave a lower ratio than 

 Kubanka. 



The water requirement ratio for several important 

 varieties of each cereal at Akron, Colorado, is given 

 below : 



TABLE V. THE WATER REQUIREMENT RATIO 

 FOR DIFFERENT CEREALS 



282. Evaporation. It has been known for some time 

 that the minimum annual rainfall required for so-called 

 dry land farming, runs about 3 to 5 inches greater in the 

 southern than in the northern Great Plains. This fact 

 could not be explained until the corresponding fact of the 

 greater evaporation in the southern area was taken into 



