^{page 18 note 1} Centr. Bakt. Par., Abt. II. 1899, 5, 473—493: “Ueber die Nitrification des organischen Stickstoffes.”Google Scholar

^{page 18 note 2} This Journal, 1909, 3, 233.Google Scholar

^{page 19 note 1} Fruit trees were growing on the loams and the clay but the land was kept cultivated and free from any quick growing crop.

^{page 19 note 2} Similar data for other plots will be found in Table II. Pouget and Guiraud (Compt. Rend. 1909, 148, 725Google Scholar), working at the School of Agriculture, Maison-Carrée, Algeria, found

^{page 23 note 1} This Journal, 1913, 5, 197.Google Scholar

^{page 32 note 1} On June 4th, 1910, the dunged mangold plots 1—0 and 2—0 contained respectively 16 and 19 parts of nitrogen as nitrate per million of soil; by July 27th these amounts were reduced to 7 and 5 respectively.

^{page 33 note 1} Warington, R., “Lost Fertility: the Production and Loss of Nitrates in the Soil,” Trans. Highland Agric. Soc. 1905, 17 (5th series), 148–181.Google Scholar

^{page 38 note 1} Russell, , this Journal, 1910, 3, 241.Google Scholar

^{page 39 note 1} A similar experiment has been made at Woburn and a distinct residual effect is obtained.

^{page 45 note 1} Leather, J. W., “Records of Drainage in India.” Memoirs of the Dept. of Agric. in India, 1912, II. 101.Google Scholar

^{page 46 note 1} Jensen, C. A., “Seasonal nitrification as influenced by crops and tillage.” U.S. Dept. of Agric, Bureau of Plant Industry, Bull. 173, 1910.

^{page 47 note 1} Löhnis, F. and Sabaschuikoff, , Centr. Bakt. Par. II. Abt. 1908, 20, 322—332Google Scholar and also Löhnis, F., Vorlesungen über landwirtschaftliche Bakteriologie, 1913, p. 340.Google Scholar

^{page 47 note 2} Müntz, A. and Gaudechon, H., “Le reveil de la Terre,” Compt. Rend. 1912, 154, 163—168.Google Scholar

^{page 47 note 3} The method was to inoculate soil taken at various dates into soil sterilised at 100° and then to find the amount of nitrification that had taken place. Unfortunately no account was taken of the ammonia produced nor was there any recognition of the special effect of such heated soil in inhibiting the development of the nitrifying organisms.

^{page 47 note 4} See Russell, and Hutchinson, , this Journal, 1913, 5, pp. 167 et seq.Google Scholar

^{page 48 note 1} Russell, and Golding, , this Journal, 1912, 5, 27;Google Scholar Russell and Petherbridge, ibid. 1912, 5, 88.

^{page 48 note 2} Russell and Hutchinson, loc. cit. p. 168.

^{page 51 note 1} Trans. Highland Agric. Soc. 1905, 17, pp. 175 et seq.Google Scholar

^{page 51 note 2} Lyon, T. Lyttleton and Bizzell, James A., Journal of the Franklin Institute, Jan.—Feb. 1911, “The Relation of certain Non-leguminous Plants to the Nitrate Content of Soils.” (All their figures are quoted as NO₃ but for convenience of comparison I have also reduced them to N.)

^{page 52 note 1} “Records of drainage in India,” Leather, J. Walter. Memoirs of the Dept. of Agric. in. India, Chemical Series, 1912, II, 63—140.Google Scholar

^{page 52 note 2} Traité de chimie Agricole, M. Dehérain, pp. 584—599.

^{page 53 note 1} A similar result seems to have been obtained by B. Welbel in the lysimeter experiments at Ploty, Podolie, Russia. In the French summary of its 11th Report (for 1905) he states:—“Les cultures en vases montrent encore que les plantes fourragères possédent une influence individuelle sur l'énergie des procès de nitrification: ainsi l'influence de l'esparcette est supérieure à celle de la luzerne.” Unfortunately the details are given only in the Russian texts.

^{page 53 note 2} Williams', method, Trans. Chem. Soc., 1881, 39, 100.Google Scholar

^{page 53 note 3} It is not necessary to dry light soils and they can be extracted straight away with water. Heavy soils, however, do not usually allow sufficient percolation to admit of extraction until they have first been dried as directed; our Rothamsted soils, for example, have to be treated in this way as a rule. We are not prepared to say that the drying is without effect on the nitrate content, but we find that it greatly facilitates extraction and it leads to higher and more uniform results than are obtained otherwise. As a precaution, however, all the soils throughout a given investigation are invariably treated alike, and either all dried, or, if they are sufficiently pervious, all extracted in the fresh state.

^{page 54 note 1} A worn out steam oven does very well for this; if the space between the walls is filled with water it is not difficult to keep the temperature within proper limits.

^{page 55 note 1} E.g. this Journal, 1912, 5, 27.Google Scholar