Conditions Requiring Drainage. 287 



atmospheric oxygen because the roots of plants and micro- 

 scopic life tend to exhaust this supply. If the soil is not 

 drained the water in it becomes stagnant in a sense, the 

 rains which fall simply running off the surface, leaving the 

 soil water the same as was there before the rain. 



3. Farm lands must be drained in order to render them 

 sufficiently firm to permit the farm operations. 



4. Soils must be drained in order to provide room for 

 soil air. (238.) (251.) 



5. The excess of water must be removed to permit the 

 soil to become warm enough for plant growth. (268.) 

 (271.) 



356. Conditions which Require Drainage. The cases in 

 which it becomes desirable to supplement natural drainage 

 fall into five classes: 



1. Comparatively flat lands or basins upon which the 

 water from the surrounding higher lands collect. 



2. Areas adjacent to higher lands where the structure is 

 such as to permit the water which sinks into the high land 

 to flow or seep under and up through the low ground, 

 making them wet. 



3. Lands inundated regularly by the rise of tides or fre- 

 quently by the overflow of rivers. 



4. Extremely flat lands in wide areas which are under- 

 laid near the surface by a thick, close, nearly impervious 

 stratum of clay, such as were formerly old lake bottoms. 



5. Lands like rice-fields, water-meadows and cranberry 

 marshes where water is applied in excessive quantities at 

 stated times and must be removed again quickly. 



357. Deep Drainage Increases Hoot Room. No plant can 

 utilize the resources of the soil to the best advantage unless 

 there is provided for it an abundance of root room. In all 

 well drained soils the roots of most cultivated crops spread 

 themselves widely and to a depth of 2.5 to 4 or more feet. 

 When conditions are such as to permit crops to do this the 

 beet growth and largest yields result. 



