SOILS — FEKTILIZEES. 813 



all the natural factors aJffiectiug the same, singly and in total, and that each 

 of these factors is in a continual process of change. " The problems of soil 

 management are, therefore, essentially dynamic. . . . The properties of 

 the soil are not merely the sum of the properties of the components, but the 

 summation of these properties as they mutually affect and modify each other." 



It must therefore be recognized " that the problems of soil fertility are no 

 longer problems merely of soil composition or merely of a supply of plant food. 

 The great fundamental questions now are : What are the processes, physical, 

 chemical, and biological, taking place continually in the soil? What are their 

 magnitudes and what are the rates of change? How do they affect one another? 

 What are the differences between individual soils that are the expression of 

 the resultants of these interdependent processes?" 



The difference between rye and wheat soils, A. Stutzer and W. Haupt 

 (Fuhrinf/s Landw. Ztg., 6-^ (1015), No. IS-li, pp. 347-352).— In examinations of 

 eight wheat soils and four rye soils no marked difference in chemical composition 

 was observed, but mechanical analyses showed that the clay content and the 

 content of fine particles in general were greater for the wheat than for the 

 rye soils. These results are taken to indicate that, other conditions being 

 approximately equal, mechanical analysis will probably in general serve as a 

 basis for judgment as to whether a soil is better adapted to wheat or rye. 



Studies of the influence of soil condition on the bacterial life and the 

 transformation of matter in soils, H. R. Christensen {Centbl. Bald, [etc.l, 

 2. Aht., 43 (1915), No. 1-1, pp. 1-166, i)ls. 2, figs. 21; Ber. Stat. Forsogs Virks. 

 Plantekult., 81 (1914), pp. 321-552, pis. 2, figs. 21; ahs. in Chem. Zentbl., 1915, 

 I, No. 13, pp. 100, 701; Intermit. Inst. Agr. [Rome], Mo. Bui. Agr. Intel, and 

 Plant Diseases, 6 (1915), No. 7, pp. 923, 924; Zentbl. Agr. Cliem., 44 (1915), 

 No. 7, pp. 290-296). — A series of detailed investigations along lines similar to 

 those previously noted (B. S. R., 18, p. 720), using Remy's method of cultures 

 in inoculated solutions of mannite and a number of different soils for inocu- 

 lation, are reported. The purpose was to study the relations between soil condi- 

 tions and the activities of Azotobacter, the power of soils to ferment mannite 

 and decompose peptone and cellulose, and the nitrifying power of soil. 



It was found that the development of Azotobacter in mannite solution de- 

 pended upon the presence of basic matter, either in the solution or in the soil 

 used for inoculation. In no case was a growth of Azotobacter obtained with a 

 base-free medium, but when the carbonates of calcium or magnesium were added 

 a marked growth of Azotobacter was obtained in the solutions inoculated with 

 raw cultures of Azotobacter. This is taken to indicate that the growth of Azo- 

 tobacter in an inoculated lime-free mannite solution may indicate the presence 

 of basic matter in the soil and that the method may serve to indicate the need 

 of a soil for lime. 



Experiments using mannite solutions with and without lime showed that the 

 occurrence of Azotobacter is not so general as is commonly thought and that 

 a sure indication of the basicity of a soil or of its need for lime can not be 

 obtained by use of a lime-free mannite solution without inoculation with Azo- 

 tobacter. It is concluded that the use of inoculated and uninoculated cultures 

 will determine whether the absence of Azotobacter is due to the chemical or 

 biological conditions of a soil, and that the occurrence and distribution of 

 Azotobacter in soil are governed by its reaction and basicity. It is further 

 concluded that Azotobacter practically never exist in acid soils and only seldom 

 in neutral soils, and that the presence of basic lime and magnesia compounds 

 is especially favorable for their growth. 



Further experiments showed that a growth of Azotobacter on the addition 

 of calcium sulphate to cultures of soils which had previously showed no 



