1916] SOILS FERTILIZEES. 515 



24 in., 68.86 lbs. per acre. "Plat 32 shows considerable accumulation of soil 

 acids to a depth of 24 in. At this depth there was found in [the corn soil] 

 3,221, [clover soil] 1,800, and [wheat soil] 2,.500 lbs. per acre 7 in., expressed in 

 terms of calcium carbonate required to neutralize the acids present. The de- 

 crease in the acid content of the surface 3 in. before and after the rain was as 

 follows: [Corn soil] 1,661, [clover soil] 1,152, and [wheat soil] 847 lbs. per 

 acre, expressed in their calcium carbonate equivalent." 



Stimulating influence of arsenic upon the nitrogen-fixing organisms of 

 the soil, J. E. Gkeaves (U. S. Dept. Agr., Jour. Agr. Research, 6 {1916), No. 11, 

 pp. 389-^16, figs. 5). — In addition to the findings noted in a previous report 

 (E. S. R., 32, p. 720), this report, prepared at the Utah Experiment Station, 

 brings out that " arsenic can not replace phosphorus in the vital process of the 

 nitrogen-fixing organisms, but it can in some manner liberate the phosphorus 

 from its insoluble compounds. This may be either a direct or an indirect action. 

 Arsenic stimulates the cellulose ferments, and these in turn react upon the 

 activity of the nitrogen-fixing organisms. The nitrogen-fixing powers of soil 

 extract, of filtered soil extract, and soil dried for some time are only slightly 

 stimulated by arsenic, showing that arsenic acts mainly by the removal of a 

 thermolabile body which occurs in the soil." 



Can soil be sterilized without radical alteration? D. A. Coleman, H. C. 

 Lint, and N. Kopeloff (Soil Sci., 1 (1916), No. 3, pp. 259-274. figs. 2).— Pre- 

 liminary experiments conducted at Rutgers College on clay-loam soil to de- 

 termine (1) the effect of intermittent sterilization of soil by dry heat, (2) the 

 relative sterilizing efficiencies of volatile chemical substances when used as soil 

 antiseptics, and (3) the effect of volatile antiseptics applied in partial vacuum 

 and under pressure at 80° C, are reported. 



It was found that " intermittent sterilization by means of dry heat at 82° 

 for five successive days in moist soil almost completely decimated the bacterial 

 flora of the soil. This was accomplished with but a slight change in the chemi- 

 cal constitution of the soil, as indicated by the amount of water-soluble solids. 

 Ordinary steam sterilization under pressure causes a change 16 times as great. 

 There is a strong indication that the application of volatile antiseptics either 

 in partial vacuum or under a combination of heat and pressure, if repeated for 

 more than three successive days, would achieve complete soil sterilization with- 

 out involving any radical alteration in the chemical constitution of the soil." 



A list of 14 references to literature bearing on the subject is appended. 



The effect of partial sterilization on plant growth, W. T. McGeokge 

 (Hawaii Sta. Rpt. 1915, pp. 37, 38).— Pot experiments with red clay and a 

 sandy soil high in organic matter growing onions, millet, and cowpeas are re- 

 ported. " These soils were treated as follows : Heated in sunlight, in an oven 

 at 80, 110, and 165° C, and in an autoclave at 10 lbs. pressure. Those heated 

 in the oven were left for two hours, that in the autoclave for only one hour. In 

 addition, soils were treated with the following antiseptics at the rate of 10 cc. 

 per kilogram: Carbon bisulphid, chloroform, and toluene. . . . 



"The influence of partial sterilization upon onions was very marked. Vola- 

 tile antiseptics produced a [marked] increase, while heating in the autoclave 

 was productive of a substance evidently toxic toward this plant. An increase 

 in vigor of the millet plant was correlated with an increase in temperature at 

 which the soil was sterilized. The plants are more vigorous in the pots ster- 

 ilized by heat than those sterilized by antiseptics. It appears that the organic 

 substance having a toxic influence upon onions is without effect upon millet, 

 for in the pot heated in the autoclave the plants are as vigorous as any others. 



" In case of cowpeas, the increase in temperature at which the soils were ster- 

 ilized resulted in a steady decrease in vigor. WhUe the volatile antiseptic low- 



