866 STATE BOARD OF AGRICULTURE. 



.600° C, wliicli is about 30 times as great as that of normal soils. At a 

 lower moisture content this depression would be much greater. Now, 

 when it is considered that the depression of the cell sap of young cereal 

 plants amounts to a little loss than 1.00° C, it becomes at once evident 

 that the failure of the carnations to grow in these soils is undoubtedly 

 due to the great concentration of the soil solution. 



The results on the lime requirement of these Ehode Island soils seem 

 to afford a most excellent confirmation of the previous laboratory results 

 and a definite proof that the lime requirement value, as indicated by the 

 freezing point method, is due to a definite factor and this factor seems 

 to be somewhat related to crop growth. 



SUMMARY. 



a 



In the present paper there is presented the freezing point method as i- 

 new method for determining the lime requirement of the soils and possibly 

 the nature of their acidity. 



The method consists of adding to 2 grams of soil 10 c. c. of water 

 and determining the lowering of the freezing point. Then to this mix- 

 ture are added various amounts of Ca(OH)o until there occurs a change 

 in the magnitude or direction of the freezing point depression. 



The method is based upon the following principles for indicating the 

 lime requirement of soils and the nature of their acidity: (1) If a soil 

 contains a free soluble acid or acid salt its freezing point depression de- 

 creases upon adding to it various quantities of Ca(0H)2 until a certain 

 point is reached and then it begins to increase with further addition of 

 Ca(OH)o. This point is considered to be the point of neutralization of 

 the acid or acid salt and of the saturization of the soil for lime. The 

 results plot into a type of curve which is designated as an acid curve. 

 (2) If a soil, however, contains neither a soluble acid nor an acid salt 

 but possesses an absorptive power for lime, due probably to the unsatis- 

 fied silicate compounds and organic matter, the freezing point depres- 

 sion remains constant as more and more of Ca(0H)2 is added to the soil 

 until a critical point is reached and then it commences to rise with 

 further addition of Ca(OH)o. The critical point is considered to be 

 the saturation of the soil for lime. The results plot into a type of curve 

 which is designated as an absorption curve. (3) If the soil contains 

 neither a free soluble acid or acid salt, nor an absorptive power for lime, 

 i. e., it is already alkaline and saturated with bases, then the freezing 

 point depression starts to rise almost immediately upon the addition of 

 a small amount of CalOH).. The curve obtained from these results 

 is named the alkaline or no-lime-absorption curve. 



The method is simple, accurate, extremely rapid, entirely different in 

 principle from that of any other method now in vogue, and appears to 

 be very promising as it affords a direct means of studying the problem 

 of soil acidity. 



The lime requirement of over 95 different soils in their natural state 

 was determined by this method. The results show that the amount of 

 lime taken up by these soils varies greatly. 



