218 THE POTATO 



seed in pods and by having peculiar knots or 

 nodules on their roots. These nodules are formed 

 by the action of a certain group of bacteria, 

 immense numbers of which are found in each 

 nodule, which have the peculiar property of being 

 able to use the gaseous nitrogen of the air for their 

 own growth, and supplying this element as they 

 die and decay to the host plant on whose roots 

 they are located. Included in this group are al- 

 falfa, all the clovers, vetches, peas, beans, etc. 

 No other group of plants or animals, so far as is 

 now known, is thus able to make use of atmospheric 

 nitrogen. Legumes may grow in soils which are 

 rich in available nitrogen without the presence of 

 the nodule-producing bacteria, deriving their ni- 

 trogen supply directly from the soil as do other 

 crops, but have the distinctive power of being able 

 to flourish in soils poor in nitrogen if the proper 

 bacteria are present to grow upon their roots and 

 supply them with nitrogen from the air, and when 

 so grown to increase the supply of soil nitrogen 

 when plowed under as green manures." 



The potato growers of the Jersey Islands use the 

 following mixture at the rate of one ton per acre 

 in addition to animal manures, etc. : 



1000 pounds super-phosphate 

 600 " sulphate of ammonia 

 300 sulphate of potash 



100 " lime dust or sulphate of lime 



2000 pounds 



William D. Kurd states that in Maine "the 

 most common and popular commercial fertilizer 

 used for potatoes has been the one analyzing 4 



