30 Journal of Agricultural Research voi. xii, No. x 



with the 30-gm. addition. The iine sandy loam shows more "true 

 acidity" with a 20-gm. application than when 10 gm. are added, and 

 still more when 30 gm. have been applied. 



The fixation or removal from solution of phosphates is supposed to 

 be done by the bases, such as iron, aluminum, calcium, etc., in the soil. 

 The clay loam and loam soils are well supplied with very fine particles 

 of iron and aluminum compounds. They therefore have the. capacity of 

 fixing more soluble phosphate than the fine sandy loam, which has a 

 relatively low content of bases. These data are in accord with those 

 obtained by Conner on soils of Indiana. 



SUMMARY 



The hydrogen electrode has been used for indicating soil reaction on 

 a number of untreated soils in suspension. The soils experimented with 

 represent a wide range in texture of those common to the area of the 

 southeastern portion of the United States, extending from and including 

 the Appalachian Mountains to the Atlantic Ocean. The H-ion concen- 

 tration varies from almost "true neutrality" to rather excessive "true 

 acidity" in the soils. 



With the Morgan apparatus for extracting film water from soils, it 

 is shown that its reaction is the same as the free water, differing only in 

 intensity. 



The effects of certain fertilizers on the H-ioh concentration of long- 

 time-treated plots of three soils have been measured, with the following 

 results: (i) Ammonia sulphate has materially increased the H-ion 

 concentration of all plots which have received applications of this material. 

 The acidity thus developed extends often to the subsoil. (2) Sodium 

 nitrate has slightly reduced the acidity of the plots to which it has been 

 applied. (3) Potassium sulphate increases the "true acidity" when 

 applied to soils, though not as greatly as ammonium sulphate. (4) Acid 

 phosphate does not appear to have affected in either direction the H-ion 

 concentrations of field soils. (5) Lime materially increases the OH-ion 

 concentration of field plots to which it has been added. 



The acidity developed from ammonium sulphate is more intense in the 

 film than in the free water of three soils. 



Monocalcium phosphate does not change in any way the soil-film water 

 until excessive amounts are added. 



LITERATURE CITED 

 (i) AxLisoN, F. E., and Cook, R. C. 



191 7. THE EFFECT OF AMMONIUM SULPHATE ON SOIL ACIDITY. In Soil vScicnCC, 



V. 3, no. 6, p. 507-512, I fig. 

 (2) Bear, F. E., and Salter, R. M. 



1916. THE residual effects OF FERTILIZERS. W. Va. Agr. Exp. Sta. Bui. 

 160, 26 p., 2 diagr. 



