CHAPTER XV 



SECONDARY ACTIONS OF ARTIFICIAL MANURES UPON THE SOIL 



I. Loss of Calcium Carbonate. IV. Action of the Plant on the Soil. 



H. Soil Acidity. V. Final Considerations. 



III. Nitrate of Soda and Tilth. Reference. 



THE study of the interaction between the fertilising con- 

 stituents of manures and the soil begins with a paper by 

 J. T. Way in the Journal of the Royal Agricultural Society for 

 1850 (I. vol. xi., p. 313), which was followed by a second 

 paper two years later, and then by further work by A. 

 Voelcker. These investigations led to the conclusions, generally 

 adopted and acted upon, that on ordinary land the fertilising 

 constituents of manures are promptly absorbed by the soil, and 

 no loss need be feared except of nitrates and the compounds 

 of nitrogen which rapidly change into nitrates. 



Way fixed upon the double silicates in the soil the so- 

 called zeolites as the agencies causing the absorption of both 

 ammonia and potash salts, though he also showed that humus 

 must have an effect in the same direction, because of the great 

 absorptive powers of all soils rich in humus. As regards the 

 zeolites, the action is intelligible enough ; these bodies are 

 complicated double silicates of alumina and various bases, of 

 which lime is the chief; in contact with a weak solution of a 

 salt of ammonia, the lime and ammonia change place, an 

 insoluble zeolite containing ammonia being formed on one 

 side, and on the other a lime salt which goes into solution. 

 Way himself, in a later paper, concluded that carbonate of lime 

 in the soil did not intervene in the process ; but in later years, 

 as it appeared that sulphate of ammonia reduced the stock of 

 carbonate of lime in the soil, it began to be thought that there 

 must be a direct interaction between sulphate of ammonia and 



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