Section III, 1918 [21] Trans. R.S.C. 



On an Electrical Method of Determining the Lime Requirement of Soils 



By C. J. Lynde, Ph. D. 



Presented by Dr. F. T. Shutt, F. R.S.C. 



(Read May Meeting, 1918.) 



INTRODUCTION 



When a given weight of soil is shaken with a given volume of 

 water for a certain time, a soil solution is obtained which has a certain 

 electrical conductivity. 



If an equal weight of the soil is shaken for an equal time with an 

 equal volume of a dilute fertilizer solution of known electrical con- 

 ductivity, a soil-fertilizer solution is obtained which has a different 

 electrical conductivity. 



If we assume that the conductivity of the soil solution is the 

 same in both solutions, we can calculate the conductivity of the 

 fertilizer solution in the soil-fertilizer solution. If this calculated 

 conductivity is less than the conductivity of the original fertilizer 

 solution, we may assume that part of the fertilizer has been absorbed 

 by the soil ; if it is greater, we may assume that soluble salts have been 

 dissolved from the soil. 



Theory 



The theory upon which this series of experiments is based is as 

 follows : 



If a soil lacks a certain fertilizer, for example K, P, Ca or N, it is 

 probable that it will absorb this fertilizer from solution, and the 

 greater the lack the greater the absorption. 



If this is true, then by measuring the amount of these fertilizers 

 absorbed by the soil we should be able to foretell what fertilizer the 

 soil needs and how much. 



The Experiment 



The simplest method of making a trial of the above theory 

 seemed to be that of comparing the lime requirements of a number of 

 soils found by the Rothamstead method with those found by the 

 electrical method described below. The results given in the present 

 paper are those obtained in this trial. 



