3i8 



Journal of Agricultural Research 



Vol. XVI. No. i» 



RELATIVE NUMBERS OF NON-SPORE-FORMING AND SPORE-FORMING 

 BACTERIA IN FRESHLY MANURED SOIL 



Work done by Conn {lo, table 3) on the flora of freshly manured soil, 

 previous to the present series of experiments, offers striking evidence 

 that the non-spore-forraing organisms predominate in such soil. During 

 his work the manuied soil vv^as plated at inter\"als extending over a 

 period of six months. On the third day it was found that almost 99 

 per cent of the entire flora was composed of non-spore-forming organ- 

 isms. The present work on the flora of freshly manured soil includes 

 experiments designed to verify these earlier results. 



The method of procedure in these later experiments was practically 

 the same throughout, except for a few differences in the treatment of 

 samples. Soil was mixed with fresh horse manure or fresh cow manure 

 and, with the exception of the first experiment, the manured soil was 

 then divided into two portions, one of which was placed in an open pot 

 and one in a flask plugged with cotton. In the first experiment the 

 manured soil was kept only in open pots. The moisture content of the 

 pots was controlled somewhat by frequent additions of water to replace 

 that lost by evaporation, but no allowance was_ made for this in the 

 flasks. Platings were made at frequent intervals at the first of each 

 experiment and at longer interv^als as the experiment proceeded. The 

 experiment recorded in Table I was carried on under conditions exactly 

 analogous to those under which Conn did his previous work, and its 

 purpose was the verification of that work. The experiments recorded 

 in Tables II and III were also carried on under similar conditions except 

 that soil mixed with cow manure was used as well as that mixed with 

 horse manure and samples were plated from plugged flasks as well as 

 from open pots. 



Table I. — Plate counts of the microorganisms in manured soil in open pots. Experi- 

 ment I 



[Counts indicate numbers of colonies per gram of soil] 



Time since adding 

 manure to soil. 



Total count. 



Days. 



Average . 



60, 000, 000 

 80, 000, 000 

 125,000,000 

 235,000,001, 

 45,000,000 

 43.000,000 

 35,000,000 

 50,000,000 

 55,000,000 

 85.000,000 

 45,000.000 

 95,000,000 

 18,000,000 

 20,000.000 



Actinomycetes. 



Plate count. 



4,000,000 

 6,000.000 

 5,000,000 

 6,000,000 

 5,000,000 

 4,000,000 

 12,000,000 

 13,000,000 

 12, 500,000 

 8, 500,000 

 13,000,000 

 8,500,000 

 5, 500, 000 

 5.000.000 



Per- 

 centage 

 of total 



flora. 



II. I 

 9-3 

 34-3 

 36. o 



32.6 

 TO. O 

 29.0 

 8.9 



30-5 



25- o 



16.3 



Non-spore formers. 



Plate count. 



56,000,000 

 74.000,000 

 116,000,000 

 220,500,000 

 38,500,000 

 36,500,000 

 23,000,000 

 35,000,000 

 42, 500,000 

 76, 500,000 

 32,000,000 

 83,500,000 

 II, 500,000 

 15,000,000 



Per 



centage 

 of total 

 flora. 



92.5 

 92.5 

 92. 7 

 93- 5 

 85- S 

 85.0 

 65. 7 



70. o 

 77-4 

 90. o 



71. o 

 88.0 

 63- 8 

 75.0 



81.6 



Spore formers. 



Plate coimt 



None. 



None. 

 4.000,000 

 9, 500,000 

 1,500,000 

 2, 500,000 



None. 

 2,000,000 



None. 



None. 



None. 

 3,000,000 

 1,000,000 



None. 



Per- 

 centage 

 of total 



flora. 



3-3 

 3-9 

 3-4 

 S- 7 



3- I 

 5- 7 



