Identifier: forestphysiograp01bowm (find matches)
Title: Forest physiography; physiography of the United States and principles of soils in relation to forestry
Year: 1911 (1910s)
Authors: Bowman, Isaiah, 1878-1950
Subjects: Physical geography Forests and forestry Soils
Publisher: New York, J. Wiley & sons (etc., etc.)
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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ration thuseffected. The succession of changes through which organic matterpasses in the processes of nitrification and denitrification is shown inthe accompanying diagram. Fig. 9. It presents in summary form theprincipal changes that have thus far been described. The immensely important conclusion has recently been establishedthat all soils contain groups of protozoa which feed upon living bacteriaand restrict their numbers, thus acting as beasts of prey.^ Their preda-tory activities seriously restrict the limits of nitrogen production even ■when the amount of organic matter in the soil is greatly increased.Happily a remedy has been found in heating or in treatment with anti-septics. Crop increases of 30% have been effected by a 48-hour treat- 1 E. W. Hilgard, Soils, 1907, p. 147. 2 Berthelot and Andre, Comptes Rendus Academie de Paris, 114, i8g2, pp. 41-43.s A. D. Hall, The Fertility of the Soil, Science, n. s., vol. 32, 1910, pp. 370-371. HUMUS AND THE NITROGEN SUPPLY OF SOILS 89
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Fig. 9. — Diagram indicating the nitrogen changes in the soil produced by the action of bacteria. Thearrows indicate the course of the changes which various groups of bacteria may produce in the nitrogencompounds of the soil. A, action of ammonifying bacteria which change organic nitrogen to ammonia;B, action of nitrifying bacteria which change ammonia to nitrite; C, action of nitrifying bacteria whichchange nitrite to nitrate; D, assimilation of nitrate by green plants; E, action of denitrifying bacteriawhich change nitrate to nitrite; F, action of denitrifying bacteria which change nitrite to ammonia;G, action of denitrifying bacteria which change ammonia to nitrogen gas; H, action of bacteria whichchange nitrogen gas into proteid nitrogen; I, action of bacteria which in symbiosis with leguminousplants change nitrogen gas into proteid nitrogen; K, action of bacteria which in symbiosis with certainnon-leguminous plants change nitrogen gas into proteid nitrogen. 1 Yearbook, Dept. Ag

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