194 



because the ground near the belt may 

 be substantially better or poorer than 

 that far out in the field. A farmer with 

 a shelterbelt 40 years old may not re- 

 member how the different parts of the 

 field varied in productivity before there 

 was a shelterbelt there. 



This variability of production within 

 fields has made so difficult the determi- 

 nation of average shelterbelt gains in 

 the fields measured from 1935 to 1941 

 by the Lake States Forest Experiment 

 Station that the entire mass of data is 

 being restudied. Predictions as to what 

 will be shown by analyses not pre- 

 viously tried may be erroneous. 



In general, however, it appears that 

 a field protected by a single-row shel- 

 terbelt, equivalent to the Osage-orange 

 hedge so common in Nebraska and 

 Kansas, will show a net gain in yield 

 equivalent to the crop on an area as 

 long as the belt and as wide as its 

 height, after allowance for shading and 

 sapping. Any belt of greater width will 

 be profitable for protective purposes 

 alone, then, provided its width between 

 the outside stems does not exceed its 

 height. 



While it seems apparent that wider 

 belts add somewhat to the benefits, it 

 is probable that the narrow belt yields 

 the greatest return on the land oc- 

 cupied, if the value of the timber 

 products is low. Benefits arise from 

 several different causes, and in con- 

 sequence are unlikely to be the same 

 in all directions from north-south and 

 east-west belts. Areas west of belts pos- 

 sibly benefit less than those in other 

 directions; in northern parts of the 

 Plains, where the snowfall is heavier, 

 greater benefits apparently are pro- 

 duced than in the central or southern 

 areas. 



Winter grains and other early crops 

 may benefit more from the snow held 

 on the field, near the belt, than from 

 other causes, while corn possibly bene- 

 fits most by protection from hot, drying 

 winds. The final results may be some- 

 what different from these predictions, 

 and in any case they apply only in the 

 area from the Dakotas to Kansas, and 



Yearbook of Agriculture 1949 



not to the drier portions of those States 

 or to better- watered regions. Except for 

 1936, when only a few measurements 

 were made, the period does not include 

 any years of serious drought. 



OTHER CROPS besides wheat and 

 corn show good response to shelterbelt 

 protection. An investigation of eight 

 cottonfields in western Oklahoma and 

 northern Texas showed an increase of 

 17.4 percent above normal between 

 and 5H, and 7.9 percent increase be- 

 tween 5H and 10H (with H represent- 

 ing a horizontal distance of one tree 

 height from the edge of the belt) . The 

 normal yield of cotton grown beyond 

 the zone of tree protection was 288.6 

 pounds of lint to the acre. 



In California, one- and two-row 

 eucalyptus windbreaks are said to be 

 effective in protecting citrus fruits from 

 bruising and dropping for a total dis- 

 tance of 5 to 7 times the average height 

 of the trees. The trees easily attain 

 heights of 60 to 80 feet within 10 to 

 20 years after planting. 



H. E. Wahlberg, of Orange County, 

 Calif., reports returns from 20 citrus 

 groves grown under windbreak pro- 

 tection as averaging $445.48 an acre. 

 On 20 unprotected citrus groves, the 

 return was only $271.34 an acre. Ac- 

 cording to those figures, a grower could 

 use 1 acre of trees on a 10-acre plot 

 for windbreak purposes and still get 

 $1,295.92 more return on the remain- 

 ing 9 acres than on the unprotected 10. 



Dale Bumstead, an orchardist near 

 Phoenix, Ariz., reported that shelter- 

 belts of eucalyptus are important in 

 reducing cullage in his citrus fruit. His 

 1946 crop had a cullage of 18.5 per- 

 cent, and cullage averaged 19 percent 

 for a 3-year period. The citrus industry 

 reports that the average cullage is 

 about 50 percent. 



Dr. Arvil L. Stark, secretary of the 

 Utah Horticultural Society, is author- 

 ity for the statement that fruit will not 

 set on the windward side of trees when 

 windy conditions prevail, because bees 

 will not work in the wind. Shelterbelts, 

 by reducing winds, thus can create 



