628 STATE BOARD OF AGRICULTURE. 



centration of the soil solution is not at all increased either directly 

 by these compounds or by the formation of new compounds as in the 

 case of neutral salts. 



As far as the results of the phosphates are concerned in most of the 

 agricultural soils, they agree with the theory of Whitney and Cameron 

 that the concentration of the soil solution may not be increased by the 

 addition of these compounds, but the explanation, does not appear to 

 be the same. 



But as far as the results of the neutral salts are concerned they agree 

 neither with the theory of these investigations nor with the absorption- 

 adsorption theory which postulates that the properties of absorption- 

 adsorption of the soil tend to maintain a constant concentration of 

 solution. 



SUMMARY. 



The study of the concentration of the natural soil solution is of the 

 greatest importance as well as of the highest interest from alj stand- 

 points — the chemical, physical, physiological, and biological. Our knowl- 

 edge concerning the concentration of the natural soil solution has here- 

 tofore been obtained through indirect means, as there has been no 

 method capable of measuring it directly as it exists in the soil and con- 

 sequently its exact magnitude has not been known, especially under 

 different conditions, including variation in moisture content, fertilizer 

 treatment, tillage, season, etc. 



In the present paper the freezing point method has been suggested 

 as a new means of measuring the actual concentration of the. soil solu- 

 tion in the soil at different moisture contents and under different treat- 

 ments. The method is based upon the general principle that the freez- 

 ing point of water is lowered by the presence of soluble material and 

 that the degree of lowering is proportional to the amount of the soluble 

 material present, (non-electrolytes). The procedure consists of placing 

 a short column of soil in a glass tube 1 inch in diameter and 9 inches 

 long, inserting the bulb of a Beckmann thermometer into this column 

 of soil, then putting this soil tube into another larger glass tube and 

 allowing the soil mass to cool in a cooling bath at a temperature of 

 • — 4.5°C. After the soil mass has supercooled to about 1°C, the thermom- 

 eter is jarred or moved in the soil whereupon solidification commences 

 and the mercury thread begins to rise and continues to do so until the 

 Ijroper freezing point is reached where it remains for some time and 

 then begins to fall again. The highest temperature reached on the 

 thermometer is taken as the proper freezing point of the soil. 



It has been found that it is extremely easy to determine the lowering 

 of the freezing point of soils. The solidification can be started when 

 the soil mass is supercooled to only about 0.3 °C and it is far easier to 

 induce solidification in soils than in solutions. The depression of the 

 freezing point of soils can be measured from any maximum water con- 

 tent down to a very low water content. The minimum water content 

 probably lies slightly below the wilting coeflScient of plants. In the 

 case of quartz sand, for instance, the lowering of the freezing point can 

 be measured when the moisture content is only about 0.7%. 



