518 EXPERIMENT STATION RECOED. [Vol.36 



bacteria developed as when it was plated unheated. . . . This suggests that 

 these bacteria occur in normal soil as spores rather than in a vegetative state. 

 No increase in the total number of these organisms nor decrease in the number 

 of their spores could be detected in a pot of soil to which fresh manure had 

 been added. 



" These results throw considerable doubt on the common assumption that 

 these organisms are important ammoniflers in the soil. They raise the question 

 as to what possible soil conditions favor their growth and multiplication." 



A possible function of Actinomycetes in soil, H. J. Conn {Jour. Bad., 

 1 {1916), No. 2, pp. 197-207).— Studies conducted at the New York State Experi- 

 ment Station on the number and activities of Actinomycetes in fine sand, fine 

 sandy ioam, sandy loam, muck, stony loam, silty clay loam, loam, and gravelly 

 loam soils are reported. 



It was found that, in general, more colonies of Actinomycetes developed on 

 plates made from sod soil than on those from cultivated soil. The average 

 ratio between their numbers in neighboring sod and cultivated spots in the 

 same soil type was slightly over 2 : 1. The maximum ratio was about 6 : 1. 

 Actinomycetes averaged about 38 per cent of the total flora of sod soil, as 

 determined by means of gelatin plates, but only about 20 per cent of the total 

 flora of cultivated soil. In a study of three neighboring spots in a single soil 

 type, it was found that with few exceptions Actinomyces colonies not only 

 appeared in greater numbers from sod than from cultivated soil, but also in greater 

 numbers from old sod than from sod only two or three years old. "A probable 

 explanation for this difference in numbers seems to be that Actinomycetes are 

 active in the decomposition of grass roots." 



The relation of protozoa to certain groups of soil bacteria, T. L. Hills 

 {Jour. Bad., 1 {1916), No. 4, pp. 423-435).— Experiments conducted at the Wis- 

 consin Experiment Station on the effect of protozoa on ammonification, nitrifi- 

 cation, and nitrogen fixation in silt-loam soil are reported. 



It was found that " in the soil cultures the presence of protozoa under the 

 conditions of the experiments did not have any noticeable effect, detrimental or 

 otherwise, on the processes of ammonification, nitrification, and free nitrogen 

 fixation. In the case of the liquid cultures employed in the study of free nitrogen 

 fixation the conditions were at an optimum for the development of the protozoa, 

 and under these circumstances they limited bacterial activity as evidenced by 

 the harmful effect on the fixation of free nitrogen. Undoubtedly under these 

 conditions the protozoa were active in destroying the Azotobacter cells." 



Sterilization of the soil, R. S. Cunliffe {Estac. Expt. Agron. Cuba Bol. 29 

 {1916), pp. 17, pis. 12). — This bulletin describes methods of soil sterilization 

 used in Cuba and the results obtained. 



The fire method is considered to be crude and uncertain. The use of anti- 

 septics is expensive and is deemed inferior to the use of hot water and steam. 

 The details of the method of steam sterilization practiced at the Cuba Experi- 

 mental Station are presentetl, and it is concluded that this method has passed 

 the experimental stage to an extent to make it of considerable practical value 

 on plantations in Cuba, especially where the agriculture is intensive. 



Green manuring experiments, J. A. Voelcker {Woburn Expt. Sta. Rpt. 

 1915, pp. 15-17; Jour. Roy. Agr. Soc. England, 76 {1915), pp. 329-331).— Green 

 manuring experiments with corn on light soil are reported showing that the 

 plowing in of leguminous crops, such as tares, did not give a return equal to 

 that resulting from the plowing in of nonleguminous crops, such as rape or 

 mustard. The soils receiving tares, however, contained more moisture, organic 

 matter, and nitrogen than the nonleguminous soils. 



