27 



and alleviatiuo- the effects of drought. On the other 

 band, surface application of manure without incorpora- 

 tion with the soil results in great loss of the valuable 

 portions of the manure and is ordinarily a wasteful 

 method of application. 



INOCULATION. 



.Ufalfa belongs to that family of plants able to derive 

 a large part of their nitrogen from the gaseous nitrogen 

 of the air. This is done through the agency of enlarge- 

 ments on the roots, called tubercles or nodules. With- 

 in these tubercles dwell countlei^s numbers of micro- 

 scopic vegetable organisms, usually referred to as nitro- 

 gen-fixing bacteria or germs. 



Eoot tubercles of alfalfa, clovers, vetches, cowpeas, 

 velvet beans, and other legiimes, are essentially ferti- 

 lizer factories engaged in the manufacture of nitrogen. 

 This is a fertilizer material, which, when bought in the 

 form of cotton seed meal or nitrate of soda or ainmon- 

 iated giiano, costs alwut 15 cents i)er pound. The im- 

 portance of the Avork of root tubercles may be realized 

 frcmi the fact that a crop of any one of these plants 

 growing on an acre usually contains from 75 to 200 

 pounds of nitrogen in roots and tops taken together. 



When the genus necessary for causing tubercles to 

 develop on the roots of alfalfa are absent from the soil 

 and from the seed, the roots of alfalfa have no tuber- 

 cles. The proper germs, which we may designate as al- 

 falfa germs, are usually absent from the sandy and non- 

 calcareous soils of Alabama, and often from other soils. 

 More frequently there are a few of the proper germs 

 present either in the seed sown or in the soil, so that 

 tubercles develop on a small proportion of the plants. 



A legiiminous plant without tubercles is a drone 



