Mar. i, 1921 Relation of Calcium Content to Soil Reaction 867 



hydrogen electrode. N/3 calcium hydroxid was added to change the 

 reaction to a higher alkalinity. The points determined were the num- 

 ber of cubic centimeters of Nj 23 calcium hydroxid needed to bring the 

 reaction (if lower) to P H 7, P H 8.3, and P H 10. 



(3) In soils of a high calcium content, a larger percentage of the cal- 

 cium is in forms soluble in these dilute hydrochloric acid solutions than 

 in soils of a low calcium content. 



(4) As a rule, soils of a high calcium content have a higher initial 

 hydroxyl-ion concentration than soils of low calcium content. 



(5) The amount of N/23 calcium hydroxid required to change a soil 

 from a lower to a higher hydroxyl-ion concentration depends more upon 

 the amount of colloidal clay present than upon the calcium content. 



(6) Subsoils, as a rule, have a higher calcium content than surface 

 soils. It required more calcium hydroxid to change these subsoils from 

 a lower to a higher hydroxyl-ion concentration than it did for the cor- 

 responding surface soils. This was true for most of the soils. The 

 exceptions were due either to a very high calcium content in the sub- 

 soil as compared with the surface soil, or to a larger amount of sand in 

 the subsoil, or to some unusual condition of the soil and subsoil. 



(7) The amount of N/23 calcium hydroxid required to change the 

 acid soils to a reaction represented by P H 7, calculated in equivalent 

 pounds of calcium corbonate per acre, compares favorably with some 

 other current methods of determining the lime requirements of the soil. 



(8) In some soils the amount of calcium hydroxid, calculated in 

 equivalents of pounds of calcium carbonate per acre, required to change 

 to a concentration represented by P H 8.3 is as great as the equivalent 

 amount of acid-soluble calcium present in the soil, or greater. 



LITERATURE CITED 



(1) Call, L. E., Throckmorton, R. I., and Swanson, C. O. 



1914. soil survey op shawnee county, Kansas. Kans. Agr. Exp. Sta. Bui. 



200, p. 717-749, map. (In cooperation with Bur. Soils, U. S. Dept. 



Agr.) 

 (2) 



1915. soil survey of rEno county, Kansas. Kans. Agr. Exp. Sta. Bui. 208, 

 48 p., map. (In cooperation with Bur. Soils, U. S. Dept. Agr.) 



1915. soil survey of Cherokee county, Kansas. Kans. Agr. Exp. Sta. 



Bui. 207, 46 p., map. (In cooperation with Bur. Soils, U. S. Dept. 

 Agr.) 

 (3) 



(4)- 



1916. soil survey of jewell county, Kansas. Kans. Agr. Exp. Sta. Bui. 



2ii, 36 p., map. (In cooperation with Bur. Soils, U. S. Dept. Agr.) 



(5) Htlgard, E. W. 



1907. soils, xxvii, 593 p., 89 fig. New York, London. 



(6) Hoagland, D. R., and Sharp, L. T. 



1918. relation of carbon dioxid to soil reaction as measured by the 

 hydrogen electrode. In Jour. Agr. Research, v. 12, no. 3, p. 139- 

 148. Literature cited, p. 147-148. 



