154 SOILS 



a more comfortable home for the roots provided in drained 

 land. 



Air gets into the soil. It has been pointed out that both 

 air and oxygen are essential for good root development, 

 as well as for high crop production. But air and oxygen 

 are excluded from the soil when water fills up all of the 

 air spaces in the soil. Drainage removes this water and, 

 hence, increases the air content of the soil. Air goes 

 just as deeply into the soil as the water table allows, and 

 as it goes down, it leaves all along its way its helpful 

 gifts scores of beneficial influences that stand for better 

 crops. 



And still two other things : It supplies the roots with 

 oxygen, and it breaks down complex substances, fitting 

 them for the call that other plants soon will make. 



Manure is made more effective. Vegetable matter and 

 other humus-forming materials are of no value in the 

 soil, until they are thoroughly decomposed and destroyed. 

 Hence, it follows that good results, from the use of ma- 

 nure, will be obtained in the highest degree only when 

 the rotting influences of the soil are best. 



For undrained soils do their work in this respect very 

 unsatisfactorily. The drained soil makes the best use of 

 manures. It has been shown frequently that chemical 

 manures are used most wisely in connection with high 

 physical improvement only, with good tillage, good 

 drainage, good cultivation, and with a free use of humus- 

 making materials. 



There is in this connection another point to be con- 

 sidered : Useful bacteria find favorable development only 

 in the presence of an abundance of oxygen ; they find 

 enjoyable the work of breaking down compounds, and of 

 building up nitrates, only when air is furnished abun- 

 dantly, and when the soil is open and warm and sweet. 



