414 



SCIENCE 



[N. S. Vol. XXX. No. 769 



The method used consisted in determining 

 the amount of ammonium sulphate the soil 

 would convert into nitrate during an incuba- 

 tion of eight days. The soils were first spread 

 out on a clean sheet of paper and allowed to 

 become air dry, being carefully protected 

 against dust during this time. To 50 grams 

 of this soil was then added a quantity of 0.4 

 per cent, ammonium sulphate (about 5 c.e.) 

 sufficient to bring the moisture content to (or 

 a little below) the optimum for plant growth.' 

 No tests were carried on in solutions, it hav- 

 ing been our experience that nitrifying bac- 

 teria do not act normally in test solutions. 

 This fact has also been reported by Stevens 

 and "Withers.^ The amount of nitrates found 

 minus the amount originally found in the soil 

 represents the action of nitrifying bacteria on 

 the ammonium sulphate solution. 



The table shows the nitrates found by this 

 method to have been formed in thirty North 

 Carolina farm soils. 



Six tests of soil samples from other lo- 

 calities are included for comparison. It will 

 be seen that while our results substantiate the 

 point that nitrification is at a rather low ebb 

 in North Carolina soils, yet nitrifying bac- 

 teria are generally present, and if supplied 

 with suitable food would undoubtedly soon 

 multiply sufficiently to cause a normal rate 

 of nitrification. 



A comparison of samples nos. 7 and 8 is 

 interesting: no. 1, having a low nitrifying 

 power, was from a portion of a field where 

 crimson clover formed no nodules, and the soil 

 gave a pinlc reaction ; no. 8, showing fairly ac- 

 tive nitrification, was from another portion of 

 the same field, gave no reaction to litmus, and 

 root nodules occurred in average numbers. 

 This is typical of much unpublished data 



^The samples were placed in salt-mouth bottles 

 stopped with a wet plug of cotton to maintain 

 even moisture conditions, and were incubated 

 eight days at 30° C. Distilled water (100 c.c.) 

 was then added to the soil, bottles shaken for 

 fifteen minutes, allowed to settle, filtered, and the 

 clear solution tested by the phenol-disulphonic 

 acid method, as described in Bureau of Soils Bul- 

 letin No. 31, p. 40. 



'Science, N. S., XXVII., No. 704, p. 991. 



NlTBiriOATION IN NORTH CABOLINA SOILS 



upon soils from other regions and leads us to 

 believe that nitrification, nodule formation 

 upon certain species of legumes, and the lit- 

 mus reaction are correlated. 



Karl F. Kellerman, 

 t. r. eobinson 

 Bureau of Plant Industry, 

 Washington, D. C. 



SECOND ANNUAL SPRING CONFERENCE OF 

 THE GEOLOGISTS OF THE NORTH- 

 EASTERN UNITED STATES 

 On April 23 and 24 a conference of the geolo- 

 gists of the northeastern United States was held 

 in Philadelphia, Pa., at the invitation of the 

 Mineralogical and Geological Section of the Acad- 

 emy of Natural Sciences. Two sessions for pre- 



