122 SOIL CONDITIONS AND PLANT GROWTH 



TABLE XXXIII. CALCIUM COMPOUNDS IN SOIL (SHOREY, FRY & HAZEN (263)). 



The Soil Water or Soil Solution. 



The soil retains by absorption and surface attractions some 

 I o to 20 per cent, of its weight of water, distributed as films 

 over its particles. This water is of obvious importance as the 

 medium through which plants and micro-organisms derive 

 their food ; indeed, it may be regarded as the culture solution 

 for the plant. Its relationship to the mineral matter is dis- 

 cussed by Cameron (65^, d, and e) and the displacements of 

 equilibrium under the influence of climate, plant roots, etc., by 

 Nolte (216). Several methods have been used for extracting 

 the solution in order to determine its composition. 



As often happens the pioneer work was done in France : 

 Schloesing in 1866 (245*) devised a method which is still 

 often used displacement of the soil solution by means of 

 water. 



Displacement Methods. Schloesing placed 30-35 kgms. 

 of freshly taken soil in a large inverted tubulated bell jar and 

 poured on it water coloured with carmine, this being done to 

 simulate the action of rain. The added water at once dis- 

 placed the soil water and caused it to descend so that it could 

 be collected : a sharp horizontal line of demarcation between 

 the added and the original water persisted throughout the ex- 

 periment even when 8 days were occupied in the descent. A 

 typical analysis of the displaced liquid in milligrams per litre 

 was : 



