EXPERIMENT STATION BULLETINS. 821 



Using the Veitch method as a standard for comparison, the freezing 

 point method shows that the soils and especially the loams, clays and 

 mucks or peats, require far greater amounts of lime to satisfy completely 

 their unsaturated compounds than the former method does. It appears 

 that this maximum requirement as obtained by the freezing point method 

 represents the true lime requirement of soils. By true lime requirement 

 is meant the total maximum amount of lime required hp the soils to 

 neutralize any of their soluhle acid or acid salts, and to satisfy their 

 al)Sorption-adsorj)tion phenomena for Ca{0H)2- 



While the freezing point method probably indicates the true lime re- 

 quirement of soils, no claim is made that it is necessary to add all that 

 amount of lime to the soils ; this point will ultimately have to be decided 

 in the field, using the plant as the indicator. As previously intimated, 

 probably no laboratory method, including the freezing point method, 

 could ever be expected to designate definitely how much lime should be 

 added to the soil. This is clearly obvious from the fact that the plant 

 is used as an indicator to determine the effects of acidity and basicity 

 upon its growth, and since it is found that different plants are affected 

 differently by these qualities. All that a laboratory method might ever 

 be expected to do, at least from the practical standpoint, is to show the 

 maximum lime requirement of the soils and then apply the lime to these 

 soils according to the requirement of the crops planted. This certainly 

 appears to be the most rational and intelligent procedure. HoAvever, the 

 experience of various observers goes to indicate very strongly that heavy 

 applications of lime increase the growth of most crops very markedly, 

 and these quantities are in accordance with those indicated by the 

 freezing point method. 



In the present bulletin, therefore, there is presented the freezing point 

 method as a new method for determining the lime requirement of soils 

 and possibly the nature of their acidity ; also the principles and descrip- 

 tion of the method ; and some of the experimental data obtained. 



PKINCIPLE OF THE METHOD. 



As already stated the principle of the freezing point method for de- 

 termining the nature of soil acidity and lime requirement is based upon 

 the following facts: (1) That if a soil contains a soluble acid or acid 

 salt its freezing point depression decreases more or less regularly and 

 gradually with the increase in the amount of Ca(OH)o added until the 

 points of neutralization and saturation are reached and then it begins 

 to increase. (2) If on the other hand a soil contains neither a soluble 

 acid nor an acid salt but possesses an absorptive power for lime, due 

 probably to the unsatisfied silicate compounds and organic matter, the 

 freezing point depression remains constant as more and more of Ca(0H)2 

 is added to the soil, until the absorptive power is satisfied and then the 

 freezing point depression commences to rise. (3) Finally, if the soil 

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



