70 SOIL SCIENCE [BoT. Absts., Vol. VII, 



fication of ammonium sulfate, fixation of nitrogen, fixation of nitrogen by B. radicicola, and 

 yield of plants. Ammonification was decreased by gypsum and by mixtures of lime and gyp- 

 sum. Nitrification was decreased by calcium sulphate but increased by calcium carbonate 

 and gypsum together. Nitrogen fixation was stimulated by 100 pounds per acre of gypsum, 

 but larger amounts had less stimulative effect. The yield and potassium content of red clover 

 was increased by 1000 pounds of gypsum per acre, but other leguminous crops or wheat were 

 not affected. Gypsum increased the soil acidity and, in some cases, the amount of soluble 

 potassium. — W. J. Robbins. 



FERTILITY STUDIES 



457. Aston, B. C. Radio-active fertilizers and plant growth. New Zealand Jour. Agric. 

 20: 172-173. 1920. — A brief review of work in England and America. — A^. /. Giddings. 



458. Harris, F. S. Effect of soil alkali on plant growth. (Abstract.) Utah Acad. Sci. 

 1 : 131-132. 1918. 



459. Leiningen-Westerburg (Graf zu.) Rauchschaden und einschlagige boden- 

 kundliche Fragen. [Smoke injury and related matters of soil science.] Forstwiss. Centralbl. 

 42: 18-93. 1920. — There is a close relation between soil composition and quality, and the 

 damage which may result to vegetation from various fumes and dusts. Smoke damage to 

 plants is usually indirect, as the effect of the fumes is on the soil and humus. Lime is espe- 

 cially necessary in soils exposed to acid fumes, and should be added in the cheapest waj 

 possible where soils are poor in lime; otherwise the acids will remove all the lime present. 

 This applies both to open and to forest lands. It has been computed that in the vicinity 

 of Stolberg (Rhine province) approximately 800 grams of sulphuric and hydrochloric acids 

 are deposited annually per square meter of soil. Lime also combines with poisonous zinc, 

 copper, iron, and mercury salts and renders them harmless to plants, but has little or no 

 effect on arsenic compounds. Some of these compounds in small quantities stimulate plant 

 growth, but in large quantities hinder or destroy it. Dust from lime, cement, or magnesite 

 ovens, etc., may act as a fertilizer, or if in too great volume and not occasionally harrowed 

 into the soil may form a crust which will injure vegetation. Soot does not in itself injure 

 plants, but does so indirectly by sticking on the foliage and adsorbing poisonous gases from 

 the air. In case of many substances, such as calcium, magnesium, chlorine, fluorine and sul- 

 phur compounds, which are already present in soil not exposed to smoke, it is difficult to deter- 

 mine the amount of injury due to fumes, since chemical analysis of the plants will not show 

 the origin of the poisons they may contain. — W. N. Sparhawk. 



460. McCooL, M. M., and C. E. Millar. The formation of soluble substances in soils 

 taken from widely separated regions. Soil Sci. 10: 219-235. 1 fig. 1920.— Samples of air- 

 dry soils were leached with distilled water until the freezing-point depression of the soil 

 was zero. The soil was then incubated at 25 °C., and the freezing-point lowerings were deter- 

 mined after 5, 10, 30, and 60 days. Sub-soils and new soils formed soluble salts very slowly. 

 New soils are less active than somewhat older soils, and aged soils are almost inert. Soils 

 from acid regions were not more soluble than those which had weathered more. The formation 

 of soluble material increased with grinding and with treatment with sodium nitrate. — W. J. 

 Robbins. 



461. NiKLAS, H. Ubersicht uber Bayerns Bodenverhaltnisse. [Summary of Bavarian 

 soil conditions.] Forstwiss. Centralbl. 42: 123-135. 1920.— The author discusses the con- 

 struction of a general soil map for Bavaria, based on the prevailing crops grown. Complete 

 soil surveys are lacking. Soils may be classified according to climatic conditions, geological 

 origin, or to texture. For practical purposes the latter classification is the best, both for 

 agriculture and for forestry. The 434 districts of Bavaria are classified in 7 soil groups as 

 follows: (1) very heavy; (2) heavy; (3) medium; (4) heavy and light; (5) light and medium; 

 (6) light, and (7) meadow soils due to climatic conditions regardless of texture. — (1) This 

 group comprises 13 per cent of the total area of Bavaria, and grows principally wheat and 



