BULLETIN 164.] [MARCH, 1908. 



Ontario Department of Agriculture. 



ONTARIO AGRICULTURAL COLLEGE. 



LIBRARY 



— = 



LEGUME BACTERIA. ^rbej^ 



SEED INOCULATION BY CANADIAN FARMERS 



IN 1906 AND 1907. 



By S. F. Edwards and B. Barlow. 



To maintain and increase the fertility of his land, the farmer must 

 put back into the soil as much plant food as he removes in his crops. It 

 is true that most soils contain rich stores of plant food, and that through 

 tillag-e and the biological agencies in the soil this food is placed at the 

 disposal of plants. This supply is by no means inexhaustible, and as it is 

 removed from the soil by successive cropping, methods must be adopted 

 to compensate for the loss. Phosphorus, potash, and nitrogen may be 

 applied to the soil in the form of commercial fertilizers or as barnyard 

 manure. Nitrogen may also be secured from the vast supply in the 

 atmosphere through the associative action of legumes (plants belonging 

 to the bean family), and certain bacteria of the soil. These bacteria have 

 the power to penetrate the roots of seedlings of leguminous plants, to 

 multiply there, and in association with the plant, in some manner not yet 

 fully understood, to take nitrogen from the air and store it up in the plant. 

 Such plants when plowed under naturally increase the nitrogen content 

 of the soil. Evidence of the activity of these bacteria may be seen in the 

 small nodules or tubercles which form on the roots of these plants. (See 

 Fig 1). Not all plants belonging to the order Leguminosae are thus 

 affected, Dut only those belonging to the sub-order Papillionacece. Of 

 these, the commonly cultivated ones which man uses are : The clovers, 

 alfalfa or lucerne, sweet white clover, lupines, vetches, beans, soy beans, 

 peas, lentils, locust, sweet pea, and winter flat pea. Many others of the 

 same order grow wild in meadow and forest. 



This enrichment of the soil by the aid of the legumes is by no means 

 a new thing. The phenomenon has been known for centuries, some of the 

 earliest writers having dilated upon the manurial value of legumes. Only 

 in recent years, however, have we attained knowledge of the bacteria 

 associated with the legumes, and of their importance in the process of 

 assimilation of atmospheric nitrogen. Although the bacteria can, under 

 certain conditions, accumulate the nitrogen of the air apart from the 

 legume, the legume cannot take the nitrogen from the air without the 

 presence of the bacteria in its roots. 



