SPECIAL FARM TOPICS 225 



seasons' rainfall will be largely utilized for each crop, are the means 

 of securing the desired results. The dry land farmer cannot afford 

 to be at all careless about any of these operations. He should 

 also remember that every weed allowed to grow in his cultivated 

 crops saps its proportion of the moisture from the land and thus 

 robs him of a portion of his just dues. 



Usually in discussing dry-farming conditions the annual pre- 

 cipitation is the only feature of the rainfall that receives attention. 

 But there are other factors in connection with the rainfall that have 

 much to do with the successful production of crops. The seasonal 

 distribution of the rain, the rate at which the rain falls, and the 

 amount of rain that is lost through run-off from the surface all have 

 an important part in determining the percentage of the total rainfall 

 that is really available for the use of crops. Finally, the amount of 

 evaporation which takes place during the growing season determines 

 to some extent the amount of rain that is needed to produce a crop, 

 and this varies greatly in different localities. ' 



Classification of Dry-Farming Regions. Dry-farming regions 

 are naturally classified on the basis of rainfall. In this country 

 dry farming is usually considered to be confined to those regions 

 in which the annual rainfall is less than 20 inches and more than 10 

 inches. This classification must be considered as only a rough ap- 

 proximation, since dry-farming districts can not be outlined on the 

 basis of the annual rainfall alone on account of the great influence 

 of the evaporation and the monthly distribution of the rain in grow- 

 ing dry-farm crops. Furthermore, it is impossible to say just 

 where ordinary methods of farming leave off and dry-farming 

 methods begin. Dry-farming methods are usually understood to 

 mean those which lead to the conservation of moisture, but the 

 conception of what these methods actually are varies greatly in 

 different sections of the country. The dry farmer in the Great 

 Plains, where the rainfall is from 15 to 20 inches, usually gets his 

 best results with annual cropping methods combined with good 

 tillage. On the other hand, the dry farmers in that part of the 

 Great Basin where the rainfall is less than 15 inches follow the 

 method of alternate cropping and summer tillage almost<exclusively. 

 Between these two' classes there is a third operating un'der conditions 

 where summer tillage may be necessary to insure*returns on every 

 crop, but where it frequently pays to> take chances on producing a 

 crop on the land each year. 



The -method of alternate cropping and summer tillage is gen- 

 erally recognized as the most highly developed dry-farming method 

 because it gives betted returns with a lower annual rainfall than 

 other methods. There are considerable areas in central Utah that 

 are cultivated in this way where the annual rainfall does not exceed 

 13 inches. It must be remembered, however, that this is a region 

 of winter rainfall, and that the method of alternate cropping and 

 summer tillage is particularly adapted for such regions. Therefore, 

 while the method of alternate cropping and summer fallowing is 

 recognized as the most highly developed dry-farming method, it 



