666 STATE BOARD OF AGRICULTURE. 



All tlio samnlos showed a marked increase in soluble s;ill content after 

 iiicnbatinf^ sixteen days, except a silt loam taken from a poorly drained 

 area. 



In foui' of the seven soils tested th'Te was an ap[)r<'ciably greater 

 increase in the concentration of the soil soliitioii of the virgin samples 

 than of the cropped. The, cropped and virgin samples of the other three 

 soils seem to have increased at approximately the san)e rate. 



After fortj'-two days incnbation at 25° C, a distinct decrease in the 

 solnble salt content of several samples was observed. This is in accord 

 with the resnlts obtained with the Ingham county soils at high and 

 medinm water content, bnt somew^hat at variance with the data for the 

 Lenawee county soils at medium water content. To Avliat this decrease 

 in soluble salts is due is not made evident. It may lie in some cases due 

 to the utilization of the soluble material by organisms or it may be due 

 to a readsorption of the salts by the soil or to the formation of less 

 soluble substances. 



At the end of this period the virgin samples of four of the soils Avere 

 found to have larger amounts of soluble salts present than the corres- 

 ponding cropped samples. In one case the cropped sample attained 

 a higher concentration than the virgin and in the remaining soils prac- 

 tically no difference was evidenced. In conclusion it may l)e stated that 

 on the whole there is a difference in the rate of solubility of cropped 

 and virgin soils. In some cases the difference is slight and even the 

 reverse condition may exist, bnt apparently a decrease in the rate of 

 formation of soluble substances is one of the changes which soils i*sually 

 undergo as a result of long continued cropping without tlie addition 

 of fertilizing material. 



It must be noted, however, that the date of sampling of soils probably 

 has a great deal of influence upon the reaction of the soil under different 

 conditions of moisture and temperature. In other words the organisms 

 in the soil and also the salt content are factors to be reckoned with. A 

 sample of soil taken from the field in March may react differently from 

 another sample taken later on in the growing season. In fact our pre- 

 liminary studies point strongly in this direction. 



B. TEMPERATURE. 



The soils used in the investigation were those collected in Ingham 

 and Lenawee counties. Twenty grams ^f the air dry soil were treated 

 with ten cubic centimeters of distilled water in a freezing point tube. 

 One series was stored in a constant temperature chamber at 25° C. These 

 samples were agitated every week to remove gas as before described. The 

 second series of tubes were kept in ice water. These samples were also 

 aerated occasionally to allow the escape of gaseous material. 



In table 28 are given the freezing point depressions of the Ingham 

 county soil solutions and also the soluble salt content in parts per mil- 

 lion after periods of ten and thirty days at the respective temperatures. 



