170 Irrigation and Drainage 



per equal areas on three different farms as the distance 

 to the eastward of the grass fields increased : No. 1, at 

 50 feet, 574 plants; at 200 feet, 390 plants; at 400 feet, 

 231 plants. No. 2, at 100 feet, 249 plants; a*, 200 feet, 

 277 plants ; at 400 feet, 193 plants ; at 600 feet, 189 

 plants ; at 800 feet, 138 plants ; and at 1,000 feet, 48 

 plants. No. 3, at 50 feet, 1,130 plants; at 400 feet, 600 

 plants; at 700 feet, 543 plants. 



In these cases the difference in stand appears to 

 have resulted from an increasing drying action of the 

 wind. On most of the fields, the destructive effects 

 of the winds were very evident to the eye, and aug- 

 mented as the distance from the windbreaks increased. 



It appears from these observations, and from the 

 protection against drifting which is afforded by grass 

 fields, hedgerows, and groves, that a system of rotation 

 should be adopted, on such lands, which avoids broad, 

 continuous fields. The fields should be laid out in nar- 

 row lands, and alternate ones kept in clover or grass. 

 Windbreaks of suitable trees must also have a beneficial 

 effect upon the crops when maintained along fields, rail- 

 roads, and wagon roads in such places as have been 

 described, and especially in the prairie sections of the 

 sub -humid regions, where irrigation cannot be prac- 

 ticed. It is, of course, true that trees on the margins 

 of fields sap the soil in their immediate vicinity, and 

 thus reduce the yield there ; but it seems more than 

 probable that in open, windy sections their protective 

 influence, which it has been sho,wn they exert, will 

 much more than compensate for this where there is a 

 general deficiency of soil moisture. 



