614 EXPERIMENT STATION EECORD. [Vol.41 



In the untreated soils, which were washed, Icept at room temperature, and at 

 a moisture content of 1 of soil to 0.7 of water, both the rate and extent of 

 solubility vaiied considerably between the different soils, thei-e being no close 

 and consistent relationship between the solubility factor and the class of soil, 

 the organic matter content, and the fineness of particles. Practically the same 

 results were obtained when an optimum moisture content was employed and the 

 soils were kept outdoors under natural conditions, although in some soils more 

 material went into solution when the moisture content was 1 of soil to 0.7 of 

 water than when the moisture content was at optimum. There was a closer 

 relationship on the whole between the solubility factor and the state of fertility 

 or crop producing power of the soil with the former than with the latter. 



When natural soils, previously washed, and with a moisture content of 1 of 

 soil to 0.7 of water, were kept at a temperature of 53° their rate of solubility 

 was somewhat appreciably increased. In some soils, however, these factors 

 were not at all affected by the high temperature. The solubility of many soils 

 even at this high temperature continued for a long time, even 60 days, but 

 usually became constant at the end of about 30 days. 



At the ratio of 1 of soil to 5 of water the rate of solubility of natural soils 

 was also slow and the extent of solubility extremely small, the amount of ma- 

 terial that went into solution at this water content being only about half as 

 great as that at the water content of 1 of soil to 0.7 of water, although an apparent 

 equilibrium was attained at this high water content, just as with the lower 

 water content. Soils having a ratio of 1 of soil to 5 of water kept at 53° showed 

 a slight increase in the rate and extent of solubility. The solubility product, 

 however, was only about one-third as great as that of similar soils kept at the 

 same temperature but having a ratio of soil to water of 1 to 0.7, while an 

 apparent equilibrium was attained in the high ratio just as in the small ratio. 



The results of experiments wherein were used a ratio of 1 of soil to 5 of water 

 are held to indicate very strongly " that the concentration of the soil .solution 

 depends upon the relative masses of the soil and water and that the soil does 

 not possess a definite solubility like definite compounds do. The amount of 

 material that goes into solution seems to increase as the ratio of soil to water 

 is increased up to about the optimum moisture content, and then it decreases." 



Relation of minimum moisture content of subsoil of prairies to hygroscopic 

 coefficient, F. J. Alway, G. R. McDole, and R. S. Trumbull {Bot. Gaz., 67 

 {1919), No. 3, pp. 185-207). — Soil moisture studies conducted for six years at the 

 Nebraska Experiment Station are reported, in which samples of soils were used 

 taken at a depth of 6 ft. or more from the buffalo-grass formation in the semi- 

 arid southwestern part of the State and from the prairie-grass formations in 

 the eastern part of the State. The hygroscopic coefficient and the moisture 

 content were determined for every sample and the moisture condition of the 

 soil expressed as the ratio of moisture content to hygroscopic coefficient. 



The subsoils of the semiarid prairies were characterized by their persistent 

 dryness. Usually throughout more or less of the first 6 ft. a ratio of moisture 

 content to hygroscopic coefficient of 1.5 or lower was found, and frequently a 

 ratio as low as 1.1 was encountered in one or more of the foot sections. 



After droughts of unusual severity the whole of the subsoil to a depth of 6 

 ft., and in some cases of 12 ft., showed a ratio of approximately 1. There was 

 no appreciable further reduction of the moisture content when, after the sub- 

 soil had been reduced to this very dry condition, there followed a 4 or 5-month 

 period of practically rainless autumn and winter weather. After such droughts 

 the surface foot was but little drier than the subsoil. 



The subsoils of the humid prairies, on the contrary, showed no distinct re- 

 duction of the moisture content through a greater depth than 5 ft., and even 



