78 



MISCELLANEOUS PAPERS. 



in comparison. Heav\^ liming of the soil extract at the rate of about 

 6,000 pounds to the acre gave a fair growth of the bacteria, and cor- 

 responding to this result one pot that received lime in the same pro- 

 portion produced a well-noduled plant. In this same soil without lime 

 and without inoculation cowpeas formed nodules abundant^. 



A soil from Lanham, Md., gave an extract which as a culture 

 medium was distinctly unfavorable to the growth of red clover bac- 

 teria, and plants of red clover in this soil made a very sickh^ growth, 

 producing few nodules. A few pots were boiled by immersing in a 

 tub of water and blowing live steam into the water; the soil was of a 

 sandy character, so that there was little danger of puddling from this 

 treatment. The growth of red clover was markedly improved in the 

 boiled series and the roots were well noduled after inoculation. The 

 extract of this soil, sterilized b}" boiling, had proved an unfavorable 

 medium for the growth of the bacteria. It is probable, therefore, that 

 boiling the soil changed the character of the soil solution at least in 

 regard to the unfavorable materials or conditions which had inhibited 

 bacterial activity. 



Soil from Lanham, Md., was further tested with alfalfa, treating 

 the soil in three ways: (1) Lime at the rate of one ton to the acre; 

 (2) lime and one-fourth humus, composed of leaf mold; (3) humus. 

 The combination of lime and humus gave. the greatest growth and 

 most abundant nodule formation. With humus alone the growth was 

 especialh" inferior and nodules were lacking even where the soil was 

 inoculated. Inoculation doubled the number of nodules where lime 

 was used and increased them six times where both lime and humus 

 were used. 



Effect of humus and lime upon the growth of alfalfa in soil from Lanham, Md. 

 [Ten plants in each series.] 



Treatment. 





Lime alone: 



Uninoculated 



Grams. 

 0.86 

 1.56 



.5 



.8 



.73 

 2.45 



(*) 

 (*) 



0.5 



Inoculated 



1.0 



Humus alone: 



Uninoculated.. 







Inoculated 







Humus and lime: 



Uninoculated 



1.4 





8.6 



No lime; no humus: 



.3 





.5 







*Not weighed; growth so small as to be a practical failure — 2 to 5 inches as compared with 12 to 18 

 inches high in the limed pots or those containing lime and humus. 



The sterilized extracts of soil from this series of pot tests gave 

 results seemingly contradictory when used as culture media for bac- 

 teria in comparison with the growth of plants and nodules. The 



100— VIII 



