THE WINDBREAK AS A FARM ASSET. 9 



EFFECT OF THE WINDBREAK ON YIELD OF CROPS. 



The effect of a windbreak on crops is not beneficial in every respect. 

 There are certain ways in which it is plainly injurious. Trees in a 

 windbreak always spread their roots extensively into the adjoining 

 fields in search of moisture ; and they take not only the moisture but 

 some of the nitrogen content of the soil. Furthermore, by shading 

 the ground they may prevent crops from developing properly. 1 



Whether the total effect of a windbreak is good or bad depends 

 upon whether the benefits derived from its influence on wind move- 

 ment, temperature, and evaporation are greater or less than the 

 injury resulting from the sapping and shading of the ground near by. 



FIG. G. Effect of windbreak protection on quality of corn. /, In rows shaded by trees ; 

 2-7, average maximum ears from protected rows ; 8, ears from unprotected portion 

 of field. 



To determine the total effect, crop measurements have been made in 

 Nebraska, Kansas, Iow r a, and Minnesota. Average rather than excep- 

 tional conditions were measured, the object being to discover the effect 

 of those influences which are continuous and affect every annual 

 crop grown. 



Measurements made in fields of small "grain indicate that the crop 

 gain in the protected zone is sufficient to offset fully the effects of 

 shading and sapping. In a wheat field protected by a dense wind- 

 break the gain amounted to about 10 bushels per acre where the pro- 

 tection was most complete, and gradually grew less as the distance 



1 Some crops do better than others when shaded. Seeding crops, such as timothy and 

 alfalfa, are least affected ; grains which develop early in the spring, such as oats and 

 wheat, are most affected, and corn occupies an intermediate position. 



