316 The Farm Woodlot 



therefore, that even a thin hedgerow exerts an influence 

 that .can readily be measured. In fact, the presence or 

 absence of protecting belts of trees under the conditions 

 often existing on the prairies may make a difference be- 

 tween a good and a poor crop. All who are acquainted 

 with our prairie regions know that great damage is often 

 done to wheat, corn and other crops by the hot southwest 

 winds which are likely to occur in the growing months. 

 In Kansas and Nebraska in the summer of 1894, im- 

 mense tracts of corn, fully tasseled out, were killed by 

 such winds. At the same time it was noticed that when 

 corn was protected by trees or slopes of land, or when the 

 humidity of the wind was increased by passing over 

 bodies of water or clover fields, the injury was greatly 

 lessened. King found that an oak grove 12 to 15 feet 

 high exerted an appreciable effect in a gentle breeze at a 

 distance of 300 feet. 



The records show that in southwestern Minnesota in the 

 dry years of 1910-11 many of the grain fields were com- 

 pletely burned up with the exception of a narrow strip 

 north of the windbreaks. The yield from these strips was 

 sufficient to furnish seed grain for the whole farm, and in 

 one season the windbreaks more than paid rent on the 

 land they had occupied throughout their existence. 



At the Dominion Experiment Station in Assiniboia, 

 Saunders found on one occasion that windbreaks exerted 

 an appreciable influence at 50 to 80 feet to leeward for 

 every foot in height, but this was during a very severe 

 wind. The greater the velocity of the wind, the farther 

 the influence of the windbreak is felt. It probably may 

 be laid down as a general rule that windbreaks will exert 



