TILLAGE 



27 



tivation of the soil helps to retain moisture by checking 

 evaporation from the surface by means of the surface mulch 

 and by loosening up the surface soil so that any rain that 

 falls will settle into it instead of running off over the surface. 

 Need of Heat. — Seed will not germinate, neither will 

 plants grow, unless the soil has a certain amotint of heat 

 in it. Heat is necessary before chemical action can begin. 

 One can not make the weather warmer, but cultivation of 

 the soil, keeping it loose on top so as to check evaporation 



Figure 10. — Preparing the seed bed by disking. 



from the surface, helps to warm up the soil. The circu- 

 lation of air, promoted by good tillage, is also quite a factor 

 in warming the soil in the spring. The air at the surface 

 of the ground becomes warmed by the sun, and if it can 

 tjnter the soil it helps to warm that also. 



Methods of Preparing the Seed Bed.— The best seed 

 bed is formed by plowing land in the fall, so that the por- 

 tion turned over by the plow will have a chance to settle 

 down upon the soil beneath (the subsoil). Then moisture, 

 which is usually present in the subsoil, may move up 

 into the furrow slice by capillary action, as oil rises in a 

 lampwick. This moisture is often necessary to supply 



