SOIL IMPROVEMENT. 



The experiments by Prof. Wagner show, first, that 

 plants of a certain class have the power of absorbing nitro- 

 gen from the air, and converting it into such a form that it 

 serves as plant food. They show, further, how this nitro- 

 gen may be afterwards employed to the best advantage in 

 practical planting or farming. The reader, however, should 

 thoroughly understand that, though these legumes have the 

 power of absorbing nitrogen from the atmosphere, still they 

 in turn must be fed with potash and phosphoric acid to 

 promote full growth. While *it is not known exactly how 

 much potash and phosphoric acid is necessary to enable a 

 legume to gather or produce or " make " one pound of fer- 

 tilizer nitrogen, it may be estimated, by taking the compo- 

 sition of a number of staple legume crops. The following 

 table shows the pounds of plant food contained in an 

 average acre of several legume crops : 



