194 



A. F. GUSTAFSON 



It will be noted that oven-drying materially increased the total soluble 

 sohds in all of the wet samples, air-drying brought about a marked increase 

 and oven-drying the air-dry soil still further increased the total soluble solids, 

 as shown in table 4. 



In the first two columns of percentages, the increase is based on the total 

 soluble solids in wet soil but in the third, the percentage increase is based on 

 the total soluble solids in the air-dry soil. This increase calculated on the 

 same basis as the first two is, for the respective samples, 83, 177, 290, 223 and 

 534 per cent. The increase due to air-drying before oven-drying cannot be 

 due to any nitrification during the slow drying at ordinary temperature, as 

 the increase in nitrates was exceedingly slight, wholly insufficient, calculated 

 as Ca(N03)2 to account for the change. 



The marked effect of air-drying on these swamp soils may help to account 

 for the relatively high productivity of such soils after a few seasons of cul- 

 tivation, as against their low productivity when newly turned by the plow. 



TABLE 4 

 Increase in total soluble sails due to drying 



Kelley and McGeorge (40) state: 



The solubih'ty of soUs used in aquatic agriculture is abnormally high, but upon drying 

 out these become much less soluble and approach a state similar to that existing in aerated 

 soils. When such soUs are heated after drying, they seem to undergo changes of the same 

 order as are produced in dry-land (ordinary cultivated) soils. 



The work here reported, either experiment 3 or 4, is not in accord with their 

 conclusions, as these soils when air-dried, had, in every case, more soluble 

 salts than the same soils when wet. 



Experiment 4 



The object of this experiment was to study the effects of oven-drying on a 

 wide range of fine-grained soils containing varied amounts of organic matter 

 at three moisture-contents, viz., air-dry, optimum, and water-logged, with 

 the soil kept in the latter two conditions for a period of 9 weeks. 



Six soils were used, ranging in texture from clay to sandy loam: 



