No. 6. Di:PARTMENT OF AGRICULTURE. 375 



6. Inoculations of Soils. 



As soon as it was shown that root tubercle development was de- 

 pendent upon the presence in the soil of specific organisms, the 

 question of seeding the soil with such organisms was raised. The ex- 

 periments which have been conducted on seeding land with soil in 

 which the specific organisms of any leguminous tubercles are known 

 to exist, have sometimes given positive and at others only indifferent 

 results. 



The positive results have usually come from the inoculation of 

 virgin soils, moorlands or barren soils that have not previously born 

 leguminous crops. 



Salfeld,^"'^ in North Germany, obtained excellent results on the 

 large scale on recently reclaimed moorlands sown to peas and beans 

 which had received applications of lime, phosphatic slag, kainit and 

 nitrate of soda, together with small quantities of fertile loam from 

 fields that had previously born good crops of these plants. 



In this case it was probable that the soil was deficient in nodule 

 I)roducing bacteria. Freewith^"^ found that in plots containing lu- 

 pines, and inoculated with lupine soil at a rate of 1,600 to 3,200 

 pounds of earth per acre, there was an increase in yield of stems, 

 leaves and hulls of from 67 to 72 per cent. In plots containing ser- 

 radella, and inoculated with serradella soil, at the rate of 80 pounds 

 to the acre, there was an increase of yield of fodder of from 41 to 

 282 per cent. 



In the latter case tubercles were found on the roots of the plants 

 grown in inoculated soil, while they were absent in those grown on 

 uninoculated land. In this case there must have been an absence or 

 deficiency of the proper organisms present, which were supplied by 

 the soil inoculations. 



Soils which have been previously uncultivated are more likely to 

 respond to soil inoculation than those which have been under tillage. 

 Thus Schniftes^"^ found that when cultivated clav soil was inocu- 

 lated with earth containing bacteria from the root tubercles of 

 lupines no favorable results were obtained. But when soil pre- 

 viously uncultivated was inoculated in the same way the increase 

 of yield was from 11 to 32 per cent. 



Otis,^*^^ of Kansas states that soy beans have been grown for eight 

 years at the Kansas Station, but during that time tubercles were not 

 found on their roots. Accordingly he secured soil from Massachu- 

 setts in which tubercle bearing soy beans had been grown. This 

 soil was used to inoculate the Kansas soy beans. All the inoculated 

 plants showed tubercles; there was also, as compared with uninocu- 

 1.1 ted plants, a greater diameter of the lower part of the stem. Analy- 

 ses of the crop showed also a slight increase in nitrogen, protein and 

 water content. 



