RELATION OF THE CALCIUM CONTENT OF SOME KAN- 

 SAS SOILS TO THE SOIL REACTION AS DETERMINED 

 BY THE ELECTROMETRIC TITRATION 



By C. O. Swaxson, Associate Chemist, W . L. Latshaw, Analytical Chemist, and E. L. 

 TaguE, Protein Chemist, Department of Chemistry, Kansas Agricultural Experiment 

 Station 



The importance of the soil reaction has led to the development of 

 numerous methods for testing the neutrality, acidity, or alkalinity of the 

 soil, and, if the soil is acid, for determining quantitatively the amount of 

 agricultural lime necessary to add to the soil in order that it may have the 

 reaction required for maximum crop production. No attempt will be 

 made to review the literature on this subject, and only a few citations will 

 be given. 



Of the different tests designed simply to determine qualitatively the 

 reaction of the soil, the litmus paper test is one of the oldest, best known, 

 and probably most extensively used. This test has been subjected to 

 much criticism, but this is probably due more to bad paper and faulty 

 use than to intrinsic defects in the method. The official or Hopkins 

 method {15, p. 20) 1 has been used for most of the acidity work done thus 

 far on Kansas soils. It was found, however, that in some cases the indi- 

 cated lime requirement appeared too low when studied in connection with 

 the known cropping conditions of the soil. The well-known Veitch 

 method (14) is probably the best quantitative measure of the lime require- 

 ments of the soil at the present time. There are several other methods 

 proposed to determine the lime requirements of the soil, and each has its 

 advocates. The strong advocate of any method is usually very free with 

 his objections to some other method. All methods are limited in their 

 application, and faults are often found with methods because the users 

 extend the application further than the originators intended. 



One difficulty in determining the soil reaction is to obtain the soil solu- 

 tion in the same concentration as it exists around the soil grains. Various 

 methods have been proposed for securing this solution, but none have 

 received general acceptance. Another factor is the facility with which 

 the optimum reaction for best crop production is maintained in the soil. 

 The concentration of the soil solution is in a state of continuous change. 

 The film of water surrounding the soil grains in a soil of optimum water 

 content tends to become saturated with the salts present in the soil. The 



1 Reference is made by number (italic) to ' ' Literature cited, ' ' p. 867-808. 



Journal of Agricultural Research, Vol. XX, No. n 



Washington, D. C Mar. 1, 1921 



xa Key No. Kans. -23 



(855) 



