64 ELEMENTARY AGRICULTURE 



a post-hole in such soil it will soon fill with water to 

 within a foot or so from the top. The level of the 

 water in this hole will be the free water level, and if 

 it comes very near the surface no crop can be expected 

 to do well there. 



Wet Soils Are Cold Soils. In wet soils a large 



A PIECE OF MARSHY LAND BEFORE IT WAS DRAINED. 



amount of heat is used in evaporating part of the 

 water, and so much is required to raise the tempera- 

 ture of what remains that these soils never become 

 warm. Often such soils are sour, and cannot become 

 sweet until the water is drained off and the heat and 

 air let in. Sometimes it is even necessary to sow lime 



