THE SOIL 75 



four to five tons of manure from the standpoint of 

 nitrogen (manure contains 10 lbs. of nitrogen per ton). 

 This together with the tonnage that it produces, ex- 

 plains why sweet clover is becoming so widely grown for 

 improving the soil in the humid sections. The suc- 

 culence of the plant renders it easily and quickly decom- 

 posed by the bacteria, making possible the turning 

 under of very great amounts. This then furnishes a 

 large amount of organic matter, and the nitrogen 

 through bacterial action becomes available to succeed- 

 ing crops. The result is that the corn or wheat crops 

 following are frequently doubled, and the effect is not 

 limited to the one year following, but is apparent for 

 several years through increased yields. Such practice 

 must come into vogue in the Prairie Provinces when the 

 organic matter and nitrogen supply need replenishing. 



It should again be emphasized that in order to secure 

 nitrogen from the air the legumes must he inoculated. 

 The bacteria may already be present in some soils and 

 if so they will make their presence known by forming 

 nodules on the roots of the young plants. If the nodules 

 are not formed, it is positive proof that the bacteria are 

 not present, and upon such soils artificial inoculation, 

 either applied as a culture to the seed or applied by 

 spreading and disking in some well-infected soil from 

 a field known to be inoculated must be resorted to. 



In applying inoculation to the seed different kinds of 

 nodule bacteria must be used for certain legumes. Al- 

 falfa and sweet clover require one kind, peas and vetch 

 take another, while the true clovers, red clover, mam- 

 moth clover, white clover, alsike clover, require still 

 another. The bacteria which produce nodules on the 

 roots of alfalfa and sweet clover will not produce 



