16 AGRICULTURE IN THE SEMIARID GREAT PLAINS. 



least prevent as high wind velocities as prevail on the level prairies. 

 Amarillo, Tex., is on a level plain and receives the full sweep of the 

 wind. The conditions at this station may be more representative 

 of the open country under discussion than those at the other stations, 

 yet it seems probable that if there were records on the open prairies 

 farther north they would lie between the figures given. For com- 

 parison, the record at Peoria, 111., is also given. 



EFFECT OF WIND ON AGRICULTURE. 



High wind velocity has an important bearing on agriculture. It 

 has a positive value as a source of power for pumping water and is 

 occasionally utilized to run feed grinders and other small machinery. 

 It also enables the farmer to cure feed quickly and in excellent condi- 

 tion, but the beneficial results fade into insignificance when com- 

 pared with the damage done. On many days it is a great hindrance 

 to labor, especially if hay or grain is to be handled; it blows the soil 

 badly, sometimes removing several inches from bare fields in a short 

 time. This drifting absolutely prohibits summer tillage on light 

 soils; the blowing sand cuts off crops and the wind does much dam- 

 age by whipping and splitting the leaves. All of these facts men- 

 tioned, however, are of small importance when compared with the 

 effect of wind on the evaporation of water from the soil and from 



plants. 



The significance of high wind velocity becomes more apparent 

 when its effect upon the rate of evaporation and the consequent dry- 

 ing effect upon soil and plants are considered. Everyone knows that 

 the air takes up water much more rapidly on a windy day than on 

 a calm one, but to get any definite relation between evaporation on a 

 still day and on a windy one is very difficult. Prof. Thomas Russell's 

 experiments with instruments constructed for the purpose gave the 

 following results for evaporation from a water surface: ^ 



With the wind at 5 miles an hour evaporation is 2.2 times as rapid as during a calm. 

 With the wind at 10 miles an hour evaporation is-3.2 times as rapid as during a calm. 

 With the wind at 15 miles an hour evaporation is 4.9 times as rapid as during a calm. 

 With the wind at 20 miles an hour evaporation is 5.9 times as rapid as during a calm. 

 With the wind at 25 miles an hour evaporation is 6.1 times as rapid as during a calm. 

 With the wind at 30 miles an hour evaporation is 6.3 times as rapid as during a calm. 



While the wind can not affect the loss of water from the soil to any 

 great depth at anything like the ratios specified, there is no question 

 that the amount of water required for the best development of plants 

 increases materially as wind velocity increases. 



1 Report of the Chief Signal Officer, War Department, 1888, p. 170; also Monthly Weather Review, U. S. 

 Signal Service, 1888, p. 235. 

 215 



