6 The Bulletin. 



present in the soil, naturally or added, to supply their needs in this 

 direction. 



With season and soil favorable to plant growth, the conditions 

 required to enable alfalfa, as well as other legumes, to be able to use 

 free atmospheric nitrogen is the presence, on the roots, of knots, 

 nodules or tubercles (see Fig. 4), and within these the presence and 

 activities of millions of bacteria or micro-organisms which are able to 

 take and combine the free nitrogen of the air into combinations that 

 can be taken up by the host plant and elaborated into building mate- 

 rial for its different tissues. It should be remembered, however, that 

 all legumes, especially when growing on rich soils, will frequently 

 make luxuriant growth without the presence of such nodules on the 

 roots and the activities they represent; but will be unable to secure 

 and use nitrogen, except that present in the soil in an available form. 

 When grown under these conditions, leguminous plants will add noth- 

 ing to the soil except what they have taken directly from it. Alfalfa 

 and other legumes have each a specific species of nitrogen-gathering 

 bacteria that should be present in or be added to a soil on which it is 

 proposed to grow the different ones ; for when these specific germs or 

 bacteria are present in sufficient numbers the plants will make their 

 best growth and do their most effective work in gathering nitrogen 

 for the benefit of the farmer and for the improvement of his land. 

 It should be remembered that, although inoculation is generally nec- 

 essary for successful alfalfa growing in North Carolina, it cannot in 

 any way make up for any deficiencies in drainage, fertilization, prep- 

 aration of the soil or subsequent management of the crop. The 

 successful carrying of these bacteria, germs, or micro-organisms into 

 any soil, either naturally or artificially, is known as inoculation. 



Any one of the four methods outlined below may be used in the 

 inoculation of soils for alfalfa culture : 



By Use of an Infected Soil. — In this method usually from 100 to 

 500 pounds of surface soil, from a field on which alfalfa has been 

 grown successfully with the formation of a large number of nodules on 

 the roots, is taken and scattered uniformly over and harrowed into the 

 field on which it is proposed to grow alfalfa, putting the soil on pref- 

 erably at the time or just before the seed are sown. It has also been 

 demonstrated that soil taken from a field on which either bur clover 

 (see Fig, 3) or sweet clover has grown with the formation of a large 

 number of nodules on their roots, will prove as effective inocula- 

 ting agent for alfalfa in new surroundings as soil from an alfalfa 

 field ; in other words, it seems to be pretty definitely settled that the 

 bacteria that inoculate alfalfa, bur and sweet clovers are identical or 

 practically so. The dangers attending the use of soil taken from one 

 field to another for inoculating purposes are that the seeds of nox- 

 ious weeds and grasses as well as the germs of bacterial diseases like 

 root-knot. wilt. etc.. may be carried with the inoculating soil to a 



