2 



Mr. A. D. Hall and Dr. N. H. J. Miller. [Mar. 30, 



Frankland* of the drainage waters from the Broadbalk wheatfield at 

 Eotharnsted.f Although the tile drains, from the flow of which the waters in 

 question are derived, rarely lie more than 2 feet 6 inches below the surface of 

 the soil, yet the drainage water from the unmanured plot contained on the 

 average 99 parts per million of CaO, of which 84 were in the state of 

 bicarbonate, and the water from the plot receiving farmyard manure every 

 year contained 147 parts of CaO per million, of which 72 may be regarded 

 as in the state of bicarbonate. Such concentrations, representing a hardness 

 of about 17 and 26 degrees respectively, though by no means equal to 

 those of truly calcareous waters, are above the average of natural waters 

 in this country ; yet, as will be seen later, the calcium carbonate from 

 which they are derived is practically confined to the uppermost 9 inches 

 of soil. 



While such losses may be regarded as natural, it has long been known 

 that many of the substances applied to the soil under the general term of 

 artificial manures react with the calcium carbonate there present and bring- 

 about its dissolution. Liebig, for example, pointed out that the di-hydrogen 

 calcium phosphate (" superphosphate ") contained in bones made soluble by 

 treatment with sulphuric acid, reacts at once with the bases in the soil and 

 becomes again insoluble. The researches of Way J and A. Voelcker§ showed 

 further that the retention of ammonium and potassium salts by cultivated soils 

 is always preceded by a double decomposition with calcium carbonate, the 

 bases being retained as carbonates while the acids appear in the drainage 

 waters combined with calcium. A. Voelcker's analyses of the Rothamsted 

 drainage waters,|| when dealing with the plots receiving salts of ammonium, 

 potassium, etc., as manures, show the same reactions taking place on a large 

 scale. 



Again, the process of nitrification, going on in all normal soils, requires 

 some base to combine with the nitrous and nitric acids produced by the 

 oxidation of the ammonia and other nitrogen compounds.^ In an ordinary 

 way this base is supplied by calcium carbonate, hence a further source of 

 loss to the calcium carbonate of cultivated soils. 



The soils of the Rothamsted experimental plots afford peculiar facilities for 

 the study of the rate at which these losses of calcium carbonate, both natural 



* ' Journ. Roy. Agri. Soc.,' 2nd Series, vol. 18, 1882, p. 14. 

 t See Table X. 



t 'Journ. Roy. Agri. Soc.,' 1st Series, vol. 11, 1850, p. 313, and vol. 13, 1852, p. 123. 

 § ' Journ. Roy. Agri. Soc.,' 1st Series, vol. 21, 1860, p. 105, and vol. 25, 1864, p. 333. 

 || Loc. tit. 



1 1 Instruction sur l'etablissement des Nitrieres,' Paris, 1777 ; Warington, ' Trans. 

 Chem. Soc.,' 1879, p. 429. 



