28 WINDBREAKS. 



usually think that the east side is more favorable for crop growth. 

 That reason for this belief exists is shown in the discussion of heat, 

 page 65. 



A comparison of various crops shows that corn and alfalfa are the 

 most tolerant of shade, and, therefore, the best producers near a 

 windbreak. This is hardly the result to be expected, since both 

 wheat and oats make their earlier development at a time of the year 

 when the sunlight is less intense than that demanded by corn, and 

 it is quite probable that the measured damage to these smaller grains 

 represents the combined effects of shading and sapping. The impor- 

 tance of the latter factor is shown in the case of alfalfa (diagram 14) 

 during a period when no rain fell and strong competition for moisture 

 is known to have existed. It should also be remembered that wheat 

 and oats develop at a time when the apparent position of the sun is a 

 good way to the south, and when, therefore, the shadow on the north 

 side of the windbreak Vould be much wider than at midsummer. 



In many cases it was found that crops immediately beyond the 

 shaded zone derive a benefit from the protection afforded by the trees. 

 This resulted from the greater warmth in the area protected from 

 wind and may, to a very slight extent, offset the damage from shad- 

 ing at the outer limit of the shadow. The zone of damage is appreci- 

 ably less in the case of a dense grove than in that of a belt or row of 

 trees which does not have so strong an effect upon temperature. 



A remarkable case of crop growth very close to trees is illustrated 

 in diagram 13, where the growth of corn on the west side of various 

 tree species is compared. This shows very clearly the value of the 

 narrow, conical crown of coniferous trees as exemplified in Austrian 

 pine, which shades a lesser area than one which becomes larger 

 toward the top. 



REMEDIES. 



The loss to crops from shading may be reduced by any of the 

 following means: 



(1) By planting, in a strip including all of the shaded zone, crops 

 whose value is not dependent upon the production of seeds, such as 

 blue grass, timothy (see Table 3), clover, alfalfa, Kafir corn, and 

 fodder corn. The production of seeds in any plant requires more 

 favorable conditions than does the growth of the vegetative parts. 

 In Kansas an area 34 feet wide next to a row of cottonwood trees 

 (illustrated in PL IX, fig. 2) gave a yield of 3 tons of Kafir corn 

 fodder, worth $6 a ton, or about 1 J tons to the acre. Practically all 

 of this strip would have been wasted had the owner of the land planted 

 corn or any other grain crop upon it. 



(2) By planting in windbreaks, or at least in that portion nearest 

 the field crops, narrow and light crowned trees. Cottonwood is both 



