THE SOIL AND SOIL FORMATION 87 



the furrow-slice and the roots of crops must feed in the 

 subsoil, not being able to get food from the dry, porous 

 furrow-slice. For this reason spring plowing for spring- 

 sown grains in dry regions sometimes serves as a more 

 open, more efficient dust blanket than the more compact 

 fall-plowed furrow-slice, and thus sometimes enables the 

 farmer to produce better crops than autumn plowing, 

 which is ordinarily the better practice in humid regions. 

 The stubble standing on the land over winter in a windy 

 country often holds snow which, upon melting, largely 

 enters the soil, leaving it more moist in the spring than 

 would be the wind-swept fall-plowed land. The looser 

 spring-plowed furrow-slice, then, better conserves water 

 from melting snows and from spring rains. 



On the other hand, the loose furrow-slice affords very 

 poor conditions for seeds to germinate, and, under most 

 conditions, the better results come from having the 

 lower part of the furrow-slice compact and the upper 

 part kept open by cultivation to serve as the blanket of 

 loose earth, or dirt mulch, to retard evaporation. Under 

 very dry conditions the deep, loose furrow-slice is so open 

 and dry that seeds will not germinate ; and a heavy rain 

 is required to make the furrow-slice sufficiently moist to 

 provide the necessary moisture to start the seeds. A still 

 heavier rain is required in order that moisture may pene- 

 trate to the solid earth below the furrow-slice, there to 

 become a part of the stored-up water of the subsoil. 



The moldboard or disk plow inverts and pulverizes 

 the soil, and mixes into it such stubble and weeds as 

 may have grown, and such manure or other fertilizers 

 as may have been applied to it. The weight of the 

 earth, the action of water, bacteria and other agencies 

 which encourage decay, bring the coarse vegetable mat- 

 ter and the lower part of the furrow-slice into a compact 

 mass closely adhering to the subsoil. The cultivating 

 implement again loosens the upper part of the furrow- 



