812 EXPEEIMENT STATION RECORD. 



chroococcum as the cause of the browu coloration of the spots (E. S. R., 25, 

 p. 815). 



The origin of the " niter spots " in certain western soils, R. Stewakt ami 

 W. Peterson (Science, n. ser., 43 (1916), No. 1097, pp. 20-24). — This is a reply 

 to the above, in which the authors reiterate their original theory regarding the 

 origin of the brown niter spots (E. S. R., 33, p. 121). They conclude "that 

 the nonsyrabiotic bacteria are not responsible for the production of the nitrates 

 noted in the niter spots of the affected soils of the arid "West and their presence 

 there is only incidental and of no more economic importance than their more 

 abundant occurrence in other normal niter-free soils of the arid regions. The 

 nitrates present in the niter spots are the direct result of the leaching and 

 concentrating action of the ground water iipon the nitrates preexisting in the 

 country rock adjacent to or underneath the soil of the affected area. . . . 

 The color is due to the solvent and decomposing action of the nitrates upon 

 the old organic matter or humus in the soil." Experimental data are cited in 

 support of the argument. 



The variation of the fertility and productivity of the soil under the in- 

 fluence of natiiral conditions and dry air storage, K. Gedboits (Trudy Selsk. 

 Khoz. Khim. Lab. St. Petcrb., 8 (1914), PP- 144-199; abs. in Sclsk. Khoz. i 

 IjQsov., 245 (1914), Aug., pp. 630-633; Zhur. Opytn. Agron.. (Russ. Jour. Expt. 

 Landw.), 15 (1914), No. 4, pp. 307, 308; Jntermt. Inst. Agr. [Rome'l, Mo. liuh 

 Agr. Intel, and Plant Diseases, 6 (1915), No. 1, pp. 37-39). — Pot experiments 

 with oats and flax on soils stored in dry air from one to six years following 

 1903 are reportctl, in which no fertilization, complete fertilization, complete 

 fertilization without nitrogen, and complete fertilization without phosphoric 

 acid were practiced. 



A gradual increase in the oat crop without fertilizer with length of storage 

 was observed, except in the fifth year of storage. " The same effect also oc- 

 curred in the pots without nitrogen and without phosphate. AVith the com- 

 plete fertilizer the greatest yield was obtained in the first year ; there was then 

 a considerable decrease in tlie second year, followed by a gi'adiial increase, 

 though the yield of the first year was never reached. In the case of flax 

 with a complete fertilizer the harvest increased regularly during the four years 

 after the first year, then remained almost constant. With the other .series the 

 changes corresponded to those of the oats." 



As a check on the above experiments a series was conducted in which soils 

 collected in various years were all tested in the same year (1908). "Tii«>se 

 experiments and many others carried out during a period of years show that 

 the yield is always in direct relation with the length of storage of the soil. 

 Chemical analysis shows a slight increase in the percentage of phosphoric acid 

 soluble in 2 per cent citric acid and in acetic acid. In 1904 the citric acid 

 soluble phosphoric acid was 0.0078 per cent and in 1909 the same soil gave 

 0.0096 per cent. The percentage of phosphoric acid in the oats and flax was also 

 increased with the duration of storage of the soil. . . . Chemical analysis 

 showed similar results with respect to nitrogen. . . . 



"These results lead to the conclusion that storing the soil in dry air increases 

 its productivity in proportion to the period of storage, and also increases in a 

 corresponding degree the percentage of phosphoric acid and niti'ogen in the 

 crop." 



The development of a dynamic theory of soil fertility, F. K. Cameron 

 (Jour. Franklin Inst., ISl (1916), No. 1. pp. 27-'/.0, figs. 2).— The author re- 

 views some of the more important features of the existing knowledge of soil 

 fertility and points out that soil management involves the consideration of 



