64 



WINDBREAKS. 



ture of the ground surface. Hence at this season the air and the 

 soil of a protected zone are cooler than they are in the open, while 

 under the trees radiation is retarded and the temperature is higher 

 than in the open. 



Table 11 presents in the first two columns the average of 17 daily 

 readings of soil temperature during the period of increasing warmth, 



DIAGRAM 32. Effect of dense windbreak on temperature of the soil at depth of 20 inches 



and in the last two columns the averages of 13 hourly readings dur- 

 ing two days in the period of rapid cooling of the earth. The same 

 results are expressed graphically in diagram 32. 



TABLE 11. Effect of windbreak on soil temperatures at a depth of 20 inches. 



i Eesults of studies made in cooperation with the Nebraska Agricultural Experiment Station. 



The temperature of the ground in the spring and summer is affected 

 by a windbreak as it affects the air temperatures during the hours 

 of insolation; and during fall and winter the effect of the windbreak 

 upon soil temperatures is the same as its effect upon nocturnal air. 



