EXPERIMENT STATION BULLETINS. 



285 



Alfalfa, however, is a new crop, with few exceptions never having been 

 grown in the same field before, hence the need of introducing the bac- 

 teria artificially. The lack of inoculation has been found to be respon- 

 sible for a very large percentage of the failures in the earlier seedings 

 of alfalfa in Michigan. Even at the present time when difalfa is being 

 seeded so commonly and the chances are so much more favorable for 

 inoculalion by natural means, the artificial inoculation is practically 

 essential to the securing of a successful seeding. 



There are several wavs in which the bacteria mav be introduced into 

 a new field e. g. by the application of soil from a field which has 

 grown one or more tubercle bearing crops of alfalfa ; by the use of 

 pure cultures, which ai-e generally a])plied to the seed; by the bacteria 

 being carried by the seed from the old field to the new; by the growth 

 of closely related species with which the same bacteria are associated; 

 by the application of alfalfa manure; and by various natural means, 

 such as moving water, wind, etc. The chief objections to the first 

 method are the possible iuLroduction of noxious weed seeds and in some 

 cases the cost of transportation and api»lication. This method has, 

 however, given very satisfactory results, the farmers' reports as sum- 

 marized in Table VII indicating that it is somewhat more reliable than 

 to use the pure cultures. In using this method care should be exercised 

 to get soil in which tubercle bearing plants are growing and to avoid 

 exposing the soil to the sunlight. It is preferable to apply it on a 

 cloudy day or at dusk and cover at once. The more of the inoculated 

 soil that is applied the more certain of having suflicient bacteria so 

 that every plant will develop the nodules in its early growth, but in 

 case the soil is secured at considerable expense 400 or 500 lbs. per 

 acre will answer very well. The use of pure culture is by far the most 

 common method of inoculation now being used. It is inexpensive, easy 

 of application and gives very satisfactory results. 



TABLE VII.— INOCULATION FOR ALFALFA. SOIL VS. NITRO-CULTURE. 



Method of inoculation. 



By soil from old alfalfa field or sweet clover 



patch 



By nitro-culture 



No. of 

 seedings 

 reported. 



91 

 363 



Percentage of seedings reported as 



Good. 



50.5 

 36.4 



Medium. 



37.4 

 30.9 



Poor. 



11.0 

 27.8 



Failure. 



1.1 

 4.9 



There are always some bacteria carried by the seed from the field 

 where the seed was produced. This accounts for the small spots of 

 alfalfa of rank, healthy growth frequently seen in the yellowish stunted 

 growth of the uninoculated field. If the alfalfa survives for a year or 

 two until the bacteria in these spots are disseminated by natural means 

 a satisfactory stand may result, but this method should never be de]>pnd 

 ed upon when alfalfa is being seeded on the field for the first time and it 

 is desired to secure a full stand of alfalfa. A most excellent practice, 

 however, is to seed a small amount of alfalfa with the regular seeding 

 of clover each year, as the bacteria introduced in this way will spread 

 naturally and produce a thorough inoculation by the time it is desired 



