_p_H Alkaline 10 --+-- Sterile: Alkali soil. ↑ | | 9 --+-- | | | 8 --+-- Fertile: Arable. | | Neutral 7 --+-- | | | 6 --+-- | | | 5 --+-- Potato Scab fails. | | Nitrification hindered. | 4 --+-- Barley fails. ↓ | Acid 3 --+-- Sterile: Peat. A SELECTED BIBLIOGRAPHY. [1] Berthelot, Marcellin, “Fixation directe de l’azote atmosphérique libre par certains terrains argileux,” Compt. Rend., 1885, ci., 775-84. [2] Boussingault, J. B., and Léwy, “Sur la composition de l’air confiné dans la terre végétale,” Ann. Chim. Phys., 1853, xxxvii., 5-50. [3] Cutler, D. W., Crump, L. M., and Sandon, H., “A Quantitative Investigation of the Bacterial and Protozoan Population of the Soil, with an Account of the Protozoan Fauna,” Phil. Trans. Roy. Soc., Series B, 1922, ccxi., 317-50. [4] Hellriegel, H., and Wilfarth, H., “Untersuchungen über die Stickstoffnahrung der Gramineen und Leguminosen,” Zeitsch. des Vereins f. d. Rübenzucker-Industrie, 1888. [5] Keen, B. A., and Russell, E. J., “The Factors determining Soil Temperature,” Journ. Agric. Sci., 1921, xi., 211-37. [6] Lawes, J. B., and Gilbert, J. H., “On Agricultural Chemistry, Especially in Relation to the Mineral Theory of Baron Liebig,” Journ. Roy. Agric. Soc., 1851, xii., 1-40. [7] Liebig, Justus, “Chemistry in its Application to Agriculture and Physiology,” 1st and 2nd editions (1840 and 1841), 3rd and 4th editions (1843 and 1847); “Natural Laws of Husbandry,” 1863. [8] Russell, E. J., and Appleyard, A., “The Composition of the Soil Atmosphere,” Journ. Agric. Sci., 1915, vii., 1-48; 1917, viii., 385-417. [9] Russell, E. J., and Hutchinson, H. B., “The Effect of Partial Sterilisation of Soil on the Production of Plant Food,” Journ. Agric. Sci., 1909, iii., 111-14; Part II., Journ. Agric. Sci., 1913, v., 152-221. [10] Schloesing, Th., and Müntz, A., “Sur la Nitrification par les ferments organisés,” Compt. Rend., 1877, lxxxiv., 301-3; 1877, lxxxv., 1018-20; and 1878, lxxxvi., 892-5. “Leçons de chimie agricole,” 1883. [11] Warington, R., “On Nitrification,” Part I., Journ. Chem. Soc., 1878, xxxiii., 44-51; Part II, Journ. Chem. Soc., 1879, xxxv., 429-56; Part III., Journ. Chem. Soc., 1884, xlv., 637-72; Part IV., Journ. Chem. Soc., 1891, lix., 484-529. [12] Way, J. T., “On the Composition of the Waters of Land Drainage and of Rain,” Journ. Roy. Agric. Soc., 1856, xvii., 123-62. [13] Winogradsky, S., “Recherches sur les organismes de la nitrification,” Ann. de l’Inst. Pasteur, 1890, iv., 1^e Mémoire, 213-31; 2^e Mémoire, 257-75; 3^e Mémoire, 760-71.