FIELD CROPS 457 



a condition most favorable to rapid evaporation. Undoubtedly 

 much of the loss ascribed to winterkilling may be traced to this 

 cause. 



The extent of injury likely to be done is affected by the loca- 

 tion of the field, ridges being exposed to and valleys or swales being 

 more or less protected from the full violence of the wind. Conse- 

 quently fields partly protected are less likely to be damaged than 

 are those fully exposed to the prevailing northwest winds. 



Little progress has been made in devising methods of handling 

 cultivated fields to prevent blowing. The problem is especially dif- 

 ficult for the dry-land farmer, as the fine soil mulch, which is so 

 necessary to conserve moisture, increases the danger from blowing. 

 It is necessary, as far as possible, to choose some middle courses 

 which will involve the least loss of moisture and at the same time 

 minimize this danger. Implements with cutting blades that fine the 

 soil out of all proportion to the value of the work done should not 

 be used. The disk and spring-tooth harrow are preferable, as they 

 tend to bring the larger particles and lumps of dirt to the surface 

 and allow the finer particles to reach lower levels of the soil stratum. 



It is important that some method of crop rotation be followed 

 that will supply humus to the soil, as possibly no other factor is so 

 efficient in cementing the soil particles together and preventing 

 blowing. 



Preparation of the Soil. Several methods of preparing the soil 

 for winter wheat have been advocated, such as seeding in small- 

 grain stubble without previous preparation ; seeding on corn ground 

 between the standing rows with a 1-horse drill; seeding on corn 

 ground after preparing with a disk and harrow; seeding on early 

 fall plowing; and seeding on land prepared by summer-fallowing. 



The first two methods are employed to catch and hold the snow 

 and thus prevent winterkilling. The average snowfall in western 

 Soufh Dakota is rather .light and the snow seldom stays on the 

 ground during the entire winter. For this reason the benefit likely 

 to be derived is not so great as in sections where the snowfall is 

 heavier. On the other hand, there is apparently not as much danger 

 from alternate thawing and freezing as in sections where there is 

 more moisture, so that protection is not so necessary. 



Possibly the chief difficulty likely to be encountered in grow- 

 ing this crop on any but summer-tillea land is to conserve sufficient 

 moisture in the soil to germinate the grain and properly maintain 

 its growth until the spring rains begin. The same difficulty also 

 applies to summer fallow not properly cultivated or when the rain- 

 fall is so deficient that no moisture can be stored in the soil. The 

 autumn precipitation is usually very light and so distributed that 

 it is often insufficient to start the crop. It frequently happens that 

 there is sufficient moisture to germinate the grain but not enough to 

 maintain its growth, in which case it may be greatly injured or 

 killed by continued drought. On the other hand summer tillage 

 is likely to increase the danger from blowing, as the tilth necessary 



