384. 



Journal of Agricultural Research 



Vol. XII, No. 6 



Table IV. — Effect of incubation at laboratory temperature on depressions of freezing 



point 



It will be evident from Table IV that in the majority of cases there 

 has been a distinct increase in the depression of the freezing point under 

 the conditions of storage. It is significant that at the end of the storage 

 period the uncropped soils still maintain their superiority with regard to 

 the concentration of the soil solution. The time at which the sample 

 is taken may in some cases influence the further changes taking place at 

 laboratory temperatures. This suggestion is supported by the data for 

 soil loB. The samples taken in November gave a much greater increase 

 in concentration after standing than was the case with the sample taken 

 in December. Doubtless these differences may be associated \\-ith con- 

 ditions favorable for nitrate production, but the extraction experiments 

 have shown that other elements are increased in solubility simrltaneously 

 with the increased production of nitrates. 



EFFECT OF CARBON-DIOXID GAS ON CONCENTRATION OF SOIL 



SOLUTION 



The increase in concentration of the soil solution noted above, as well 

 as the seasonal changes, may probably be related to the activities of 

 microorganisms and their production of carbon dioxid. Several experi- 

 ments were therefore undertaken to demonstrate the effect of carbon/ 

 dioxid gas on freezing-point depressions. A sample of soil 5A containing 

 17.7 per cent of water was placed in a stoppered bottle, and a current of 

 carbon-dioxid gas was passed through the moist soil for about five 

 minutes. This treatment was repeated several times. The bottle was 

 then closed tightly and the soil permitted to stand overnight in contact 

 with the atmosphere of carbon dioxid, after which the depression of the 

 freezing point was determined and compared with another sample of 

 the soil exactly the same but not treated with carbon dioxid. The 

 control sample gave a depression of 0.083° C. and the treated soU 0.138°. 



