38 BULLETIN 481, U. S. DEPARTMENT OF AGRICULTURE. 



For crop protection the woodlot must be properly located. In 

 the absence of native timber, windbreaks, which are woodlots in nar- 

 row strips, were extensively planted for crop protection by the 

 early settlers in the great plains region. The results did not look 

 satisfactory to the farmers, because it was noticed that near the 

 windbreak the grain was stunted and poor, and a revulsion of feeling 

 against timber belts took place. There is not so much planting as 

 formerly, and in one State — Kansas — legislative action has been 

 taken providing that all hedge fences along the public highway shall 

 be cut and trimmed to not more than 5 feet high, except when pro- 

 tecting orchards, vineyards, and feed lots. 1 



To find out as accurately as possible the relation between benefit 

 and injury to farm crops from windbreaks, a detailed study of this 

 subject was made in 1908 by the Forest Service. 2 Careful measure- 

 ments were made at different distances from windbreaks of various 

 species to determine, on the one hand, the amount of harm done to 

 adjacent crops by shading, the sapping of soil moisture, and other 

 causes: and on the other hand, the amount of benefit due to protec- 

 tion from evaporation, the breaking of the mechanical force of the 

 wind, etc. At the same time, the solid contents of the trees were 

 measured and their value as wood determined. The results of the 

 study showed a good deal of variation among windbreaks of different 

 species and different degrees of density, and between rows running 

 in north-and-south as compared with east-and-west directions. In 

 general they showed that while dense windbreaks do considerable 

 damage to crops standing close to them — to a distance of once or 

 twice the height of the tree — their protection from drying winds 

 will ordinarily increase the grain yields farther away, to a distance 

 of 10 or 12 times the tree height — more than enough to make good 

 the loss. The protection is especially noticeable after heavy winds, 

 which in the absence of efficient windbreaks often ruin entire fields 

 of grain. The greatest direct benefit is obtained when the wind- 

 breaks are not closer together than a distance equal to twenty times 

 their height. Orchard trees close to windbreaks are injured by shad- 

 ing and sapping, while those farther away are benefited by protection 

 from breakage, drought, and freezing. 



The economic value of windbreaks is determined not only by the 

 prevalence of damaging winds in a region, but also by climatic fac- 

 tors affecting the growth of the trees themselves and the productive- 

 ness of the windbreak as a source of timber supply. "Windbreaks 

 very commonly occupy soils of agricultural value : and since an effec- 

 tive windbreak must consist of more than a single row of trees, the 



1 General Statutes of Kansas, 1901, sees. 3116-3118. The adoption of this statute is 

 left to popular vote in each county. 



2 " Windbreaks : Their Influence and Value." by C. G. Bates. Forest Service Bulletin 

 86, 1911 ; and " The Windbreak as a Farm Asset," by C. G. Bates, Farmers' Bulletin 788. 



