10 EXPERIMENT STATION RECORD. 



but that the force with whicli the soil absorbs alkalies varies with tlie con- 

 centration of the solutions. Brustlein' has shown that soils are not able 

 to remove alkali completely from its solution in water. These solutions 

 circulate to a considerable extent in the soils without nnderj^oing decom- 

 position. This explains how water brings to the plant the chemicals 

 needed in very great dilution. Potash and ammonia are easily retained 

 as carbonates by the soil but less readily in the form of sulphates. 



When a solution of acid phosphate of lime comes in contact with 

 sand, a portion of the phosphate is rapidly absorbed; but absorp- 

 tion is not complete for at least 25 days. Still it is believed that 

 there is little serious loss of phosphates by drainage following a heavy 

 rain even in sandy soils, while with lime and clay soils the absorption 

 is naturally more rapid and comi)lete. 



The influence of the water of the soil upon the microorganisms which 

 play a part in the fertility of the soil remains to be mentioned. The 

 experiments of Berthelot' show that the nitrogen of the air is fixed 

 through bacteria in non-sterilized soil; and Hellriegel and Wilfarth, 

 Breal, Schlossing, and Laurent have shown that the bacteroids in the 

 root tubercles of leguminous plants are able to fix free nitrogen. It is 

 known that the phenomemi of nitrification takes place in 3 steps — forma- 

 tion of ammonia, nitrites, and nitrates ^ — under the influence of bacteria, 

 yeasts, algiie, and the ferments of Winogradf^ky. Bacillus mj/coides 

 is aerobic, and able to produce ammonia in the presence of organic 

 nitrogen, but it becomes a denitrifier and anaerobic when there exists 

 in the soil rapidly reducible substances, such as nitrates.* 



These investigations show that the lower organisms play an impor- 

 tant role ill the fertility of the soil. Water in varying quantity has an 

 influence on the biology of all these organisms. Schlossing and Miintz'' 

 have shown that nitriflcation requires a certain amount of moisture, and 

 the writer's'' investigations have shown that the vitality of Bhizobiuvi 

 [.eguminosarum is influenced by the water content of the soil. For each 

 soil there is an optimum humidity. Too great dryness checks or entirely 

 prevents the iormation of tubercles. Excessive moisture produces an 

 analogous efl'ect, though less marked. The writer has shown that the 

 formation of the tubercles begins soon after the development of the 

 plant, and it is therefore of highest importance to furnish the young 

 leguminous plant with sufficient water. 



As regards the variations in ammonia formation with varying 

 proportions of water, it would appear a priori that the results should be 

 analogous to those cited in the case of nitrates. 



' Ann. Chim. ct Phys., ser. 3, vol. 56, p. 497. 



^Compt. Rend., 101 (1885), p. 775; 110 (1890), p. 558. Ann. Chim. et Phys.. ser. 6, 

 vol. 11, p. 375; vol. 16, p. 490. 



^ Eilmond Gain, Pr6cis de Chiniio Agricole, p. 74. 



••E. Marfbal, Production de I'annnonia dans le sol, 1894 (I<:. 8. R., 5, p. 614). 



'^Schliissiny-, Encycl. Chiniique de Fremy — Chimie generale (nutrition de v6g<5. 

 taux). 



e'fJev. gen. Bot., 7 (1895), p. 123. 



