DRAINAGE. 19 



(c) It is essential to the life of the organisms that transform the 



nitrogen of organic matter into nitric acid. 



(d) It prevents the action of denitrifying organisms. (Those that 

 destroy nitrogen). 



Effects of Too Much Water. 



When there is too much water in the soil it excludes the 

 air, prevents the nitrogen fixing bacteria from taking the free 

 nitrogen of the air in the soil and combining it with oxygen and 

 hydrogen to form nitric acid. 



Thus the successful growth of alfalfa, clover and other 

 legumes is impossible where bacteria cannot live. 



Effects of Too Much Drainage. 



Too much soil air in a rich soil will result in such strong 

 development of nitrates, that humus and other organic nitrogen 

 are quickly changed into soluble forms and leach away before 

 they can be utilized by the growing crops. 



Coarse sandy soils are often impoverished through too 

 much ventilation and leaching. 



Water- Drainage and Plant Growth. 



The roots of corn, oats, clover and alfalfa will penetrate 

 to a great depth if not restricted by water standing in the soil. 



If water stands near the surface of the soil, the area for 

 root development will be very small and the growth of the plant 

 above ground will correspond to the development of its system 

 of roots. 



A wet puddled soil excludes air and resists root penetration. 



A well drained soil will, in dry weather produce a better 

 crop than the same soil will produce when it is undrained. 



High, rolling or hilly land needs drainage for many of the 

 same reasons that low lands are often drained. 



The following illustration shows that water falling on cul- 

 tivated land of good tilth does not enter the tile or ditches until 

 the water in the soil rises to the level of the drains. 



