UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



AGRICULTURAL SCIENCES 



Vol. 1, No. 10, pp. 291-339 April 29, 1916 



FUNDAMENTAL INTERRELATIONSHIPS 



BETWEEN CERTAIN SOLUBLE 



SALTS AND SOIL COLLOIDS 



BY 



L. T. SHAEP 



INTRODUCTION 



While engaged in an extensive investigation of the physio- 

 logical effects of NaCl, Na2S04 and NaoCOg on crop plants as 

 grown in the Davis clay loam, in cylinders, under field condi- 

 tions, the writer observed that the soil to which the salts had 

 been previously applied became so impervious during the course 

 of the experiment as to retard markedly the rate of percolation. 

 So pronounced was this effect that during the winter and early 

 spring months all of the salt-treated soils were continuously 

 covered with standing water. The appearance of this striking 

 modification in the permeability of the soil to water in the salt- 

 treated soils, together with the inferior cultivating qualities 

 exhibited by them, impres.sed us as evidence of the fact that the 

 salt treatments under the field conditions of the experiment had 

 effected a fundamental change in the physical constitution of the 

 soil. The occurrence and nature of this change and its relation 

 to soil colloids, interior surface, and other properties of soils, 

 form the considerations with which this paper is chiefly con- 

 cerned. 



Just such an effect on the physical condition of the soil as 

 described above had been anticipated as the normal result of 

 adding NaoCOg to the soil, for this salt has generally been con- 

 ceded, by soil experts, to be an active deflocculating agent. But 



