Dec. 1. 1920 Relation of the Soil Solution to the Soil Extract 



383 



to throw further light on the relation between the soil extract and the 

 soil solution. The value of the determination made by the water- 

 extraction method rests primarily on the assumption that a logical rela- 

 tionship exists between water extracts and the soil solution. 



In the articles referred to above considerable data were presented to 

 show that in general the larger fluctuations in the total solids found in 

 1 to 5 water extracts occurred coincidently with similar fluctuations in 

 the freezing-point depressions of the moist soil. Later much more ex- 



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.005 

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Fig. 2. — Graph showing relation of fre,ezing-point depressions in soil (calculated to 17 per cent moisture) 

 to total solids extracted by 5 parts of water to 1 of soil. Individual data from seven soils composited. 



tensive observations were made on this important question, and the data 

 have been plotted in two graphs (figs. 1,2), one for the group of silty 

 clay loam soils and the other for the various fine sandy loams, the soils 

 being the same as those described in a previous article by Stewart (9). 

 The data for the individual soils have been composited for the present 

 paper. In these graphs the determinations of total solids and freezing- 

 point depressions are plotted for various time intervals, for the soils in 

 both the cropped and uncropped condition. The correlation between 

 16916°— 20 i 



