34 EXPERIMENT STATION. [Jan. 



deep sub-soiling- clue to the penetration of the great tap roots of 

 the phnit ; and sei-ond, to the aocunmlation of nitrogen in the 

 roots and stnhble, drawn in the fir^^t instance from the air. It 

 Avill he understood that when an alfalfa sod is jilowed, and the 

 roots and stuhhle decay, the large amount of nitrogen which 

 thev contain becomes availal)le to succeeding crops. 



