Yields of Grain from the Pots, the Mean of Three Years' Food for 



Experiments. Plants 



With With complete dressing: 167 



complete Without phos- Without Without 

 dressing phoric acid potash nitrogen 



A glance at the table shows that among n soils, there 

 are those rich in phosphoric acid and poor in phosphoric acid, 

 rich in potash and poor in potash, but not a single one of the 

 ii soils has shown itself to be rich in nitrogen; all were es- 

 sentially poor in nitrogen. If either the phosphoric acid or 

 potash were omitted from the dressing, the yields fell regu- 

 larly, and if nitrogen were omitted the yields fell in quite a 

 striking manner. 



These experiments, also, show further to what a great 

 extent a dressing of Nitrate of Soda increased the yield when 

 the soil is hungry for nitrogen, and not the yield of straw 

 alone, but in like proportion the grain also. It is false to 

 say that nitrogen affects the yield of straw, and phosphoric 

 acid the yield of grain. The experiments show in a very 

 palpable manner that this view is incorrect. // nitrogen be 

 deficient, phosphoric acid can produce neither straw nor grain. 



An Explanation of the High Nitrogen Require- 

 ments of Soils. 



A question naturally asked would be, how it happens 

 that 1 1 soils showed such an extraordinary poverty in nitro- 

 gen? Was it accidental, or were the soils selected for the 

 purpose exceptionally poor in nitrogen? The chemical anal- 

 ysis of the four soils previously described shows them to 

 contain, on the average: 



