112 



HATCH EXPERIMENT STATION. 



[Jan. 



each plot receiving a nitrogen fertilizer receives annually 

 the same number of pounds of nitrogen. The past season 

 is the eighteenth since the no-nitrogen plots have been 

 manured with anything containing nitrogen. The curve 

 below shows the per cent, which the yield on these plots 

 constitutes of the yield on the plots manured with nitrogen. 



That the crop of potatoes on the no-nitrogen plots this 

 year amounts to 99.3 per cent, of the crop on the plots 

 receiving nitrogen is a fact of much significance. In the 

 earlier years of this experiment, as has been stated, the 

 crops following soy beans have not appeared to derive any 

 considerable benefit from the roots and stubble of this crop. 

 For this year it is believed that we must conclude the 

 benefit is considerable. This difference in the after-effect of 

 the soy beans is possibly explained in part by the fact that 

 the bacteria, whose presence is essential to the acquisition 

 of atmospheric nitrogen, are now more abundant in this soil 

 than during the earlier years when soy beans were grown ; 



