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205 



place between closely related legumes. Cross-inoculation is not 

 successful between alfalfa, clover, Canada field pea, soy bean, 

 and cowpea. Bvit even when cross-inoculation is successful, there 

 is no evidence to show that it is as efficient as when the legume 

 is inoculated with its own bacteria. The information on the 

 subject of cross-inoculation is meager 

 and the practice is not recommended. 



I 



HOW TO INOCULATE. 



There are two ways in which inoc- 

 ulation may be accomplished, the soil 

 method and the pure-culture method. 



Soil Method. -piG. 3i.— Legume bacteria, 



highly magnified. 



When we find nodules on a legu- 

 mionus crop, we know that in the soil where the crop is being 

 grown there are nodule-forming bacteria. If we take a certain 

 amount of this soil and scatter it over a new field we introduce 

 into the new field, along with the soil, some of the bacteria. In 

 practice, usually about two hundred pounds of soil broadcasted 

 on every acre will be sufficient to inoculate the field. This is a 

 simple method of inoculation and good results are invariably ob- 

 tained. There are, however, some drawbacks to it. It is not 

 always easy to get the soil, and because of its bulk it is difficult 

 of transportation. A more serious objection to the soil method 

 of inoculation is that when the soil comes from an unknown field 

 various weed seeds, diseases, and insects may be in it. In that 

 case such pests would be introduced into our field and would 

 cause trouble. Dodder, for example, may be spread in this way. 

 Therefore one should bear this in mind when considering the 

 use of soil for inoculation. The method is especially well adapted 

 for inoculating one field with soil obtained from another part on 

 the same farm. 



The writer believes that the simplest and most economical way 

 to inoculate is, not to plant and inoculate a large acreage at 

 first, but to plant one acre or less of the particular legume and 

 inoculate a part of it, leaving the other part uninoculated. If the 

 plants on the inoculated part of the field look greener and 

 healthier than those on the uninoculated part, and in addition 

 have an abundance of nodules on the roots while the plants on 

 the uninoculated part have no nodules or very few, the field 

 needs inoculation. This practice has two advantages : in the 

 first place, the farmer learns whether the soil needs inoculation 

 for the particular legume ; and in the second place, in case inoc- 

 ulation is needed, the soil from the inoculated part of the field 



