PHYSICAL INTER-RELATIONS IN SOILS 31 



When a clay or loam soil is permitted to become over- 

 dry, the plow turns it over in lumps, and no amount of 

 work can properly fit it for an immediate crop. (See 

 Fig. 20.) 



47. Correct moisture condition for plowing. Some- 

 where between the over-wet and the over-dry condition 

 is the ideal moisture point. In clay soils and loams this 

 is a capillary moisture condition, and is not the same for 



FIG. 10. A mass of the same soil as is shown in Fig. 8, but with an 

 over amount of capillary moisture, as is proved in Fig. 11. 



every soil. Every experienced farmer recognizes this 

 proper state of moisture and takes advantage of it, even 

 resorting to artificial means to prolong its period until 

 he can complete his plowing. When plowed in this con- 

 dition, with the exception of the heavy clays, the normal 

 soil falls away from the mold-board in a rather uniformly 

 mellow mass. (See Fig. 19.) When in this state, a 

 mass of the soil firmly crushed in the hand will retain its 

 position when the pressure is removed, but when a rolling 

 pressure is applied to it with the fingers, it readily crumbles. 

 (See Figs. 8, 9, 10, and 11.) 



