SOILS — FERTILIZERS. 619 



colloids, and in humus soil.s both to this cause and to humus acids. The use of 

 fertilizer salts was found to render the absorbed aluminum and iron compounds 

 soluble and thus injurious to plant growth. Over three-fourths of the soils of 

 Japan and Korea examined were found to be acid and in one-half of these the 

 acidity was due to aluminum and iron compounds absorbed by the soil colloids. 

 The highest percentage of acid soils was found among those derived from Meso- 

 zoic formations, followed in descending order by Tertiary, Paleozoic, Diluvial, 

 and Alluvial soils. Soils fi'oni so-called acid rocks were more frequently acid 

 than those derived from basic rocks, but the smallest percentage of acid soils 

 was found among those derived from volcanic ashes. 



The author tested various methods of detecting and determining soil acidity 

 and discusses their relative merits. He describes and recommends as simple 

 and reliable a potassium nitrite test. For the exact determination of acidity he 

 proposes a method based upon the fact that when acid soils are treated with a 

 neutral salt solution, preferably potassium chlorid, the aluminum and iron com- 

 l)omids absorbed by the soil colloids are set free in such form as to give an acid 

 reaction to the solution, the degree of which can be accurately determined by 

 titration with standard alkali solution. 



Acid soils were found to contain as a rule little lime, and their lime factor 

 was generally unfavorable owing to an excess of magnesia. 



Soils and subsoils, W. H. Suekzer (Mich. Geol. and Biol. Survey Pub. 12, 

 Geol. Sei: 9 (1913), pp. 130-149, pi. i).— The soils of Wayne County, Mich., are 

 classified as glacial and river clays, sand and gravel, loam, silt, and muck 

 soils. 



The glacial clays consist mainly of silt and clay with a considerable quantity 

 of fine sand. The river clays are more limited in extent than the glacial clays, 

 but their average texture is finer and much more uniform. The sand and 

 gravel soils possess relatively little available plant food, but are light and 

 easily tilled and drained. The loam soils are deemed the most valuable in the 

 county from a inirely agricultural standpoint and are adapted to the growing 

 of all crops which may be raised on either the clay or sand. The silt soils are 

 closely related to the loam but are more limited in extent. The muck soils are 

 from one-fifth to one-fourth sand and nearly two-thirds organic matter and 

 contain very little clay. They can not be utilized for agricultural purposes 

 until properly drained and their acidity corrected. 



The excessive quantities of nitrates in certain Colorado soils, W. P. 

 Headden {Join: hidus. and Emjin. Chan.. 6 (79///). Xo. 7. ;>/*. 586-o90). — This 

 article summarizes a number of articles previously noted (E. S. R., 28, p. 31 ; 29, 

 p. 621; 30, p. 818). 



The soils of the island of Luzon, A. J. Cox and A. S. ARoiJELLES (Philippine 

 Jour. Sci., Sect. A, 9 (1914), No. 1, pp. 1-50, pis. 7, figs. 4)- — The authors discuss 

 the significance of the physics, chemistry, and biology of soils in general and 

 give information based on a number of chemical and mechanical analyses con- 

 cerning the fertility of some of the agricultural sections of Luzon. 



The majority of the soils analyzed appear to be fine-grained and slightly acid. 

 The soils of the Batangas district, consisting mostly of loam or clayey loam 

 resulting from the disintegration of water-laid tuff, agglomerate, etc., are said 

 to be very fertile. The area around Batangas is made up of alluvial and lit- 

 toral deposits. The Pangasinan soils vary in texture from heavy tenacious 

 clay loam to fine silt and sand or gravel. In certain wooded districts of the 

 Mountain Province the soils are deficient in potash, and in spite of the general 

 fertility of the soil there is a rice shortage in time of drought. The soils of 

 the Cagayan A'alley, the composition of which is continually changing owing 



