MORE PLANT-FOOD ELEMENTS BECOME AVAILABLE 111 



supply of moisture in a well-drained soil than in a wet one all 

 on account of more and deeper roots. 



Not only are plants able to secure more water when they 

 develop deep roots, but they are able, also, to secure more of the 

 plant-food elements. 



3. Soil Organisms Develop Better. Water-soaked soils are 

 practically devoid of helpful organisms, while those well drained 

 are usually abundantly supplied with them (Chapter VII). 



FIG. 46. Wet and cold subsoil injured the corn crop. For many years nobody sus- 

 pected that seepage water was the cause of poor corn crops on a large portion of this field 

 even though heavy applications of manure were made. To the left, good corn; to right, 

 injured corn. (See Fig. 39.) 



4. Injurious Substances May be Removed. Proper drainage 

 may be the means of getting rid of certain injurious substances in 

 soils. In some wet marshes, acids have accumulated to such an 

 extent that the soils have become extremely acid in character. When 

 such soils are drained, the accumulated acids are leached out, 

 sometimes almost completely, during the first three or four'years 

 after thorough drainage has been established. 



The thorough drainage of alkali spots is the best treatment 

 recommended. Drainage is the method sometimes used to elimi- 

 nate injurious salts from alkali soils (Chapter IV). 



5. More Plant-food Elements Become Available. The 

 entrance of more air in the soil, a warmer soil, the development of 



