122 EXPKBIMENT^STATION EECOED. 



unless the precipitation for these months is in excess of the normal, except on 

 very rare occasions. The number of flood days increase most rapidly when the 

 precipitation during these months is about 3 in. above the normal or about one- 

 half more than the normal." 



The effect of atmospheric conditions on the hardness of rain water, S. 

 Wolff {Jour. Soc. Chem. Indus., 32 {1913), No. 7, pp. 3Jf5-347). — Examinationa 

 of samples of rain water collected near Manchester, England, showed the 

 presence of considerable amounts of calcium and magnesium salts and a high 

 degree of hardness. The author concludes that the rain water carries down 

 not only soot but other soluble or insoluble substances floating in the air, but 

 which in ordinary air analysis might not be found in such appreciable quan- 

 tities. 



SOILS— FERTILIZERS. 



The effect of partial sterilization of soil on the production of plant food. 

 H, The limitation of bacterial numbers in normal soils and its consequences, 

 E. J. Russell and H. B. Hutchinson {Jour. Agr. Sci., 5 {1913), No. 2, pp. 

 152-221, figs. 7). — Further investigations are here reported which, it is stated, 

 confirm the conclusions of previous work (E. S. R., 22, p. 121) and produce 

 further evidence " that bacteria are not the only inhabitants of the soil, but 

 that another gi"oup of organisms occurs, detrimental to bacteria, multiplying 

 more slowly imder soil conditions and possessing lower jiower of resistance to 

 heat and to antiseptics. 



" In consequence of the presence of these detrimental organisms the number 

 of bacteria present in the soil at any time is not a simple function of the tem- 

 perature, moisture content, and other conditions of the soil. It may, indeed, 

 show no sort of connection with them. Thus, rise of temperature is found to be 

 ineffective in increasing the bacteria in the soil; increase in moisture content 

 has also proved without action. The number of bacteria depends on the differ- 

 ence in activity of the bacteria and the detrimental organisms. 



" But when soil has been partially sterilized the detrimental organisms are 

 killed and the bacteria alone are left. It is then found that increase in tem- 

 perature (up to a certain point) favors bacteria multiplication and causes the 

 numbers to rise. Variations in moisture content also produce the normal 

 results on partially sterilized, but not on untreated soils. 



"The detrimental organisms are killed by any antiseptic vapor or by heating 

 the soil to from 55 to 60' C. ; they suffer considei'ably when the soil is main- 

 tained at lower temperatures (40°) for a sufficient length of time. Cooling to 

 low temperatures also depresses them although it fails to kill them. 



" The completeness of the process can be accurately gaged by the extent to 

 which the bacteria suffer. Whenever the treatment is sufficiently drastic to 

 kill the nitrifying organisms and to reduce considerably the numbers of the 

 other bacteria (as shown by the counts on gelatin plates) it also kills the 

 detrimental organisms. If the soil conditions are now made normal, and the 

 antiseptic is completely removed, rapid increase is observed in the bacterial 

 numbers and the rate of production of ammonia. A temporary or partial sup- 

 pression of the factor is, however, possible without extermination of the nitri- 

 fying organisms. ' 



" Once the detrimental organisms are killed the only way of introducing 

 them again is to add some of the untreated soil. But the extent of the trans- 

 mission is apt to be erratic, being sometimes more and sometimes less complete 

 than at others; occasionally the infection fails altogether. We have not yet 

 learned the precise conditions governing the transmission. 



