64 DRY LAND FARMING 



by the same when tilled, a result of the structure of the 

 soil grains as neither too coarse nor too fine. Some 

 soils are so fine that through impactioh they resist the 

 easy penetration of water. Such are clays of fine texture. 

 Other soils may be so open that they lose moisture by 

 leaching almost as fast as it comes to them. Such are 

 coarse sands, but these are not very prevalent. (3) It must 

 be able to retain moisture. This will follow when the 

 soil grains are neither too large nor too small, too ad- 

 hesive nor too much filled with air spaces. This condi- 

 tion is best found in sandy loam soils well supplied with 

 humus. The deeper that the soil possessed of these prop- 

 erties is, the more moisture will it contain. Such a soil 

 and subsoil will readily store a goodly supply of moisture 

 for further use, and it will also furnish ample feeding 

 ground for the roots of plants. (4) It should not have in 

 excess those elements that lead to a gumbo or an alkali 

 condition (see p. 73). Such soils are" very hard to till 

 owing to the difficulty of keeping them in a proper me- 

 chanical condition. (5) They should not be so light and 

 fine as to lift with the wind. Such a condition would add 

 greatly to the difficulty of cultivating and cropping such 

 soils in dry areas. (6) They should not wash readily 

 when rainfall is abundant. This is one of the weak 

 characteristics of many western soils. The particles are 

 so light and so little adhesive that they are easily held 

 in solution and hence are easily carried away. This is 

 often true of soils that are productive. This tendency 

 may be lessened in various ways, but more especially by 

 adding humus to the soil. (7) It should be rich in plant 

 food not only in the tillable portion but in the subsoil. 

 This characteristic is usually present in a marked degree, 

 not only in western soils but also in the subsoils that un- 

 derlie them. 



Characteristics of subsoil. In dry areas the phys- 

 ical constituents of soil and subsoil are frequently much 



