52S STATE feOARD OF AGRICULTURE. 



A thick viscous cylinder oil was used in making the extractions. 



The paraflin oil pressure method furnishes in most cases plenty of 

 solution for the necessary analytical work. In sandy soils as high as 

 74 per cent of the moisture present in the soil was obtained. 



A large amount of solution may be obtained without coming in con- 

 tact with- the oil. If it does it can be easily separated by cooling and 

 separatory funnel. 



The concentration of tlie soil solution from the same tj^pe of soil varies 

 according to the moisture content of that soil from which it is derived. 



Successive portions of tlie same extraction vary very little in their 

 physical properties, but do more in the various forms of nitrogen. 



The forms of nitrogen vary in the different solutions, since they are 

 changeable quantities. Calcium and jnagnesium also vary due to the 

 treatment and reaction, of the soil. The phosphoric acid (PO^) is fairly 

 constant. Potash (K) varies somewhat. 



A small percentage of the bacteria are removed from the soil, since 

 the soil acts as a filter. 



Anaerobic changes take place in the cylinder if it is allowed to stand 

 for a long time. 



The paraffin oil displacement-pressure method furnishes as far as we 

 are able to judge witli our present facilities, a fair representative of the 

 solution as it exists in the soil. Tlie method permits the use of a large 

 amount of soil thus a better represejitative sample. Work now in 

 progress indicates that it furnishes a valuable index of the microbial 

 changes in the soil. 



POSSIBILITIES AND LIMITATIONS. 



The soil solution is im])ortant from the plant physiologist's point of 

 view for the study of plant nutrients and balanced solutions. It opens a 

 field for the soil chemist and physicist for the study of some of the soil 

 conditions, — e. g., composition and concentration of the liquid phase 

 of the soil. To the soil bacteriologist it is important for the study of 

 microbial changes that take place in the soil, the filterable microorgan- 

 isms in the soil and of pathogenic microorganisms that may live in the 

 soil. 



The method has its limitations in that the oil does not penetrate all 

 soils and, therefore, does not give all the soil solution that might be 

 otherwise obtained. 



The amount of solution obtainable depends upon the moisture content 

 of tlie soil and upon the type of soil. The greater the moisture content, 

 the greater the amount of solution that can be obtained from the various 

 samples of similar soils. From samples of dissimilar soils having equal 

 moisture content, the proportion of the total moisture removable varies 

 with tlie soil type, the largest percentage being obtainable from sandy 

 soils and the smallest from clay soils. 



The method is still open for improvement. Certain phases of it need 

 further study, as the tyf>e of cylinder, displacing liquid, and the method 

 of ^lacking the soil in the cylinder. 



Type of cylinder — The size of the cylinder is important in obtaining 

 the best results as has been shown with a few extractions described 



