EXPEUIMENT ISTATION BULLETINS. 710 



TABLE 25. — RATE AND EXTENT OF SOLUBILITV OF NATUKAL SOILS IN DISTILLED 

 WATER WHEN TUE RATIO OF SOILS TO WATER WAS ABOUT 1 TO .70 AND MIX- 

 TURE MAINTAINED AT OR BELOW ZERO TEMPERATURE. FIGURES REPRESENT 

 FREEZING POINT DEPRESSION. 



Days. 



30 



1 



9 



6 



7 



8 



11 



14 



12 



UX 



26 



Wisconsin Superior clay 



Michigan clay loam 



Mictiigan clay loam 



California Ramona clay loam 



Michigan clay loam 



Michigan brown silt loam. . . 

 Wisconsin Miami siltloam. . 



Michigan brown siltloam 



Michigan fine sandy loam 



California Okley fine sandy loam : .008 



A glance at the above data reveals at once the fact that when the 

 soils remain frozen no material goes into solution. It is seen that the 

 depression of the freezing point at the end of 30 days is exactly the same 

 as that at the beginning. 



At this point some very important practical conclusions can be drawn 

 from the entire investigation thus far presented. It has been seen that 

 the soluble salts of the soil can be so thoroughly washed, or leached 

 away that the soil for the time being is almost devoid of soluble salts. 

 It has also been seen that the rate of solubilitv is so exceeding] v slow 

 and especially at optimum moisture content, that the soil requires not 

 only days but even weeks to accumulate any appreciable amount of salts. 

 Finally, it has been shown that when the soils are frozen the solubility 

 process completely and entirely ceases. 



From these facts the ijractical conclusions that can be drawn are 

 that during the fall months when the rainfall is very abundant, at least 

 . in many regions, the soils are quite thoroughly washed and become almost 

 devoid of soluble salts. During the winter months when these soils 

 freeze, the solubility process is entirely stopped, and consequently there 

 is no accumulation of any soluble salts. In the spring months, on account 

 of the low temperature and the exceedingly slow rate of solubilit}^ 

 the amount of material that goes into solution is very small and the 

 amount of nitrates formed also small, and consequently the plants do 

 not tiud an abundance of plant food in solution. This should and prob- 

 ably does have an important bearing on soil fertilization that is with 

 respect to the time, amount and form to apply. 



Eate and Extent of Solubility of Natural Soils Which Were Pre- 

 viously Washed and the Ratio of Soil to Water Was 1 to 5 and Mixture 

 Maintained at Room Temperature. 



Definite chemical compounds, at any given temperature, have a defin- 

 ite solubility which is independent of the relative masses of the solid and 



