PIG. 3. Effects of Turning Under a Crop of Vetch (leguminous) 

 upon the Growth of Oats. 



Both pots were supplied with potash and phosphoric equally, as in fig. 2. The 

 pot marked "Saltpeter" received its nitrogen in the form of saltpeter; the one 

 marked " Wicken " had vetch turned under, showing that it was equal to saltpeter 

 as a source of nitrogen. 



