8 



FARMERS BULLETIN 788. 



more than counterbalanced by the higher temperatures secured 

 during the day. 



Windbreaks may appear undesirable for the protection of orchards 

 in blossom or garden crops which are not hardy, because the danger 

 of still frost seems increased by the stagnation of the air on the lee 

 side. The added danger is more apparent than real, however, for 

 still frosts only occur when there is practically no wind, and a wind- 

 break can then have little effect one way or the other. Furthermore, 

 complete stagnation of the air may be helpful rather than harmful 

 if smudging is resorted to. 



FIG. 5. Wheat near the trees has been benefited by the covering afforded where snow 

 drifted in the lee of the windbreak. 



The freezing which often causes the most severe damage to 

 orchards is that which follows a cold rain or late snow. During such 

 a freeze the damage to blossoms is greatly reduced by protection from 

 wind; for evaporation which produces a rapid cooling increases in 

 proportion to wind velocity* During a freeze of this kind in 

 Nebraska in 1908, fully protected orchards yielded crops many times 

 as heavy as those without exterior protection, and even the leeward 

 side of individual trees exposed to the wind suffered much less damage 

 than the windward side. It is noteworthy also that the one storm 

 of rain and snow, with a temperature of 28 degrees, did all the 

 damage during the season, and that later frosts with lower tempera- 

 tures did not affect the orchards. 



