1916] SOILS FERTILIZEBS. . 511 



mately twelve times that of the latter, the ratio being uninfluenced by the arid- 

 ity of the climate. When the inch sections of the surface foot are considered 

 the organic carbon decreases slightly more rapidly than does the nitrogen, the 

 average ratio being 13.4 for the first and 11.3 for the twelfth inch section. 

 In the levels below the first foot also a similar difference in the rate of de- 

 crease is observed, the ratio in some cases falling as low as 6. The decrease is 

 less rapid in the western than in the eastern areas, the average organic carbon 

 content in the fourth, fifth, and sixth feet being higher in the two most wes- 

 terly areas than in the two most easterly, while that of the nitrogen is lower. 

 The decrease in nitrogen and organic carbon in the surface soil from east to 

 west . . . [is] attributed to the greater vegetative growth without a corre- 

 spondingly more rapid decay in the eastern areas. 



"The water of constitution (the difference between volatile matter and or- 

 ganic matter) decreases from east to west, the variations being concordant 

 with those in the hygroscopicity. Compared with the Russian chernozem soils 

 formed on loess, the organic carbon and the nitrogen are low both in the sur- 

 face soil and in the subsoil, the amounts found in the eastern areas being similar 

 to the minima reported for the chernozem. The subsoils from the semiarid 

 areas, in so far as the nitrogen is concerned, in contrast with the arid subsoils, 

 are as ' raw ' as those from the humid areas, not supporting a satisfactory 

 growth of nonleguminous plants." 



A list of 26 references to literature bearing on the subject is appended. 



II, Humus, humus-nitrogen, and color, F. J. Alway and M. J. Blish. — In 

 this report of studies of the humus-nitrogen and color of the soils described 

 in the foregoing article, "the gi'avimetric method for the determination of 

 humus was found in the case of the subsoils to fail to indicate the relative 

 amounts of ammonia-soluble, dark-colored organic matter present. A colori- 

 metric method is preferable for the subsoils ; in the case of the surface soils it 

 is at least fairly satisfactory for the determination of the whole of the 

 ammonia-soluble organic matter. 



"Within the surface foot the humus decreases from the first to the twelfth 

 inch and from east to west. The rate of decrease downward is independent of 

 the degree of aridity. In the second foot the decrease from east to west is less 

 marked than in the first, while in the still lower levels the humus, as deter- 

 mined gravimetrically, shows no distinct change from east to west. No 

 marked differences in the percentage of nitrogen in the humus were found be- 

 tween the soils from the most humid and those from the most arid parts of the 

 region. The soluble pigment in the surface foot was found to decrease in pass- 

 ing from east to west, while that in the third to sixth foot increases. A rela- 

 tively low amount in the surface foot with a relatively high content in the sub- 

 soil characterizes the soils from the more arid portion of the region. 



"The colors of the soil and subsoils agree in general with the amounts of 

 soluble pigment found by the colorimetric method. . . . The color of the soils 

 in the western areas is lighter, and in all the areas the dark-colored surface 

 layer is shallower than in the typical Russian chernozem. Buried soil surfaces 

 as well as the dark tongues and veins, common in the Russian chernozem, ap- 

 pear to be absent in the loess of the Nebraska portion of the transition region. 

 Gravimetric determinations show the humus of the soils of the western 

 semarid areas to be similar in amount and in distribution to that of typical 

 arid California soils." 



A list of 12 references to literature bearing on the subject is appended. 



[Composition of caliche], A. E. Vinson and C. N. Catlin {Arizona Sta. Rpt. 

 1915, pp. 567, 568).— Analyses of five samples of caliche are reported, the results 



