Soil Bacterial Types 253 



SOIL BACTERIAL TYPES AND GREEN MANURING. 

 I. L. Baldwin and A. J. Smith, Purdue University. 



In an experiment to determine the effect of calcium carbonate on 

 the biological activities of a soil, it was noted that the addition of green 

 manure seemed materially to alter the equilibrium existing between the 

 bacterial types. This point was deemed of sufficient importance to 

 justify further study and as a result an effort was made to classify the 

 bacterial types developing on agar plates from the treated and untreated 

 soils. 



Many investigators have reported the effect of various green ma- 

 nures on the number of bacteria developing in the soil and practically 

 all have found a decided increase following the addition of green manure. 

 However, few investigators have attempted to make a qualitative study 

 of this increase. Hiltner and Stomer^ in Germany, and Chester" and 

 Conn\ in this country, have carried out the most extensive work in 

 studying and classifying the soil flora. Conn, whose work is far more 

 thorough than any of the others, has classified the soil flora into three 

 main divisions, spore formers, non-spore formers and Actinomycetes. In 

 this same work. Conn reports that the addition of manure to soil dis- 

 turbs the equilibrium between the bacterial types, greatly stimulating 

 the non-spore forming group. Murray^ in 1920, reports that the addi- 

 tion of straw to the soi! does not appear to stimulate any one type more 

 than the others. Other investigators have reported similar results, the 

 effect varying with the material applied to the soil. 



The soil used in this experiment was a black sandy loam, containing 

 a rather high percentage of organic matter and with a lime require- 

 ment of about 1,600 pounds calcium carbonate to the acre. Twenty 

 gallon stone jars were filled with ten pounds each of the air dry soil and 

 treated as follows: 



Pots 1 and 6 received .500 pounds calcium carbonate per acre. 

 Pots 2 and 7 received 1,000 pounds calcium carbonate per acre. 

 Pots 3 and 8 received 2,000 pounds calcium carbonate per acre. 

 Pots 4 and 9 received 4,000 pounds calcium carbonate per acre. 

 Pots 5 and 10 received no calcium carbonate. 

 Pots 11 and 16 received .500 povmds calcium carbonate per acre. 

 Pots 12 and 17 received 1,000 pounds calcium cai'bonate per acre. 

 Pots 13 and 18 received 2,000 pounds calcium carbonate per acre. 

 Pots 14 and 19 received 4,000 pounds calcium carbonate per acre. 

 Pots 15 and 20 received no calcium carbonate. 



^ Hiltner, L., and Stormer, K. Studien uber die Bakterienflora des Ackerbodens, mit 

 besondeier Berucksichtigung ihres Veihaltens nach einer Behandlung mit Schwefelkohlen- 

 stoflf und nach Brache. Kaiserl. Gesundheitsamte, Biol. Abt. Land- u. Foistw. 3, 445-545. 

 1903. 



-Chester, F. D. Bacteriological analysis of soils. Del. Agr. Exp. Sta. Bui. 65. 1904. 



3 Conn, H. J. Soil Flora Studies. New York (Geneva) Agr. Exp. Sta.. Tech. Bui. 

 57, 58, 59, 60. 1917. 



^ Murray, T. J. The effect of straw on the biological soil processes. Soil Science, 

 12, 233-259. 1921. 



"Proc. 38th Meeting, 1922 (1923)." 



