Hence, it seemed necessary to publish a report of what has been 

 accomplished in this line at Guelph, tog-ether with a brief statement of the 

 history of the discovery of the legume bacteria, their manner of growth, 

 and how they may be utilized by the farmer. 



The Importance of Nitrogen to the Farmer. 



As is well known, nitrogen, the most important and costliest element 

 that a farmer buys or uses for plant food, can be used by most plants 

 combined only in the form of nitrates. The daily loss of this valuable 

 fertilizer is enormous, and several scientists have predicted that in the 

 course of a number of years our supply of nitrogen will be so appreciably 

 used up that the growing of wheat and other crops will be a matter of 

 difficulty. These men base their calculations on the loss of nitrogen 

 which comes from the yearly cropping of land, the waste of the sewage 

 from the great centres of populations, the loss by leaching from the soil, 

 the action of the denitrifying bacteria, and other causes ; and they also 

 show that the great natural stores of this element are being quickly con- 

 sumed for agricultural purposes. Thus the guano deposits we nearly all 

 used up, and the South American saltpetre beds are being fast exhausted. 

 Fortunately, however, there are vast stores of nitrogen in the air, the 

 atmosphere containing about four out of every five parts of this element, 

 and one of the great problems of modern agriculture has been to make 

 this store of atmospheric nitrogen available to plants, and the peculiar 

 ability of leguminous plants to assimilate the nitrogen of the air is the 

 faculty which makes them so valuable to the farmer. The legumes are 

 able to achieve this result by the aid of the bacteria which are associated 

 with them in the nodules or tubercles on their roots. 



Not only does the acquirement of the nitrogen from the air benefit the 

 legume, but it also enriches the soil and renders available considerable 

 combined nitrogen for the use of succeeding crops. Every practical 

 farmer acknowledges these facts by introducing clover or some other 

 legume in his rotation, knowing that the fertility of his soil is thus increased. 

 As a result of the investigation of many Experiment Stations it has been 

 shown that from 100 to 200 pounds per acre of nitrogen are added to the 

 soil by the growth of a crop of legumes. Putting the matter into dollars 

 and cents, the United States Department of Agriculture states that a crop 

 of nodule-bearing legumes is equal to from 800 to 1,000 pounds of nitrate 

 of soda per acre, which at the present rate for this fertilizer represents a 

 value of from $20.00 to $25.00. 



The Discovery of the Nodule Bacteria 



The Romans were fully aware of the importance of growing legumes, 

 and introduced such crops into their rotations, many writers in their time 

 drew attention to the manure-like qualities of beans, vetches, etc. Thus, 

 Pliny, a Roman writer, makes the definite statement that beans will 

 fertilize the soil of a field or vineyard as well as the very best manure. The 

 .true reason of these facts was, of course, not known at that time, but was 



