820 STATE BOARD OF AGRICULTURE, 



methods now in vogue are capable of indicating the total maximum lime 

 requirement of soils, Tlie Veitch method has been mainly taken into the 

 discussion because it is generally considered to be the standard method. 

 The other methods are based upon different principles and although the 

 individual criticisms would accordingly vary, yet the main and important 

 criticism, namely that they may not indicate the total maximum lime re- 

 quirement of the soils, is the same. It will have been noticed that 

 nothing has been said concerning the empirical nature of these methods, 

 the comparatively slight variations in methods of procedure affect the 

 result obtained markedly. The errors arising from this source, how- 

 ever, serious as they may be, are insignificant in comparison with the 

 above main objection. 



It is hoped that the foregoing critique will not be considered as a con- 

 demnation of any of the soil acidity methods, and especially of the 

 Veitch method! Indeed that is far from being the intention and desire 

 of the writer. He fully realizes and acknowledges their usefulness. In 

 offering these criticisms it is done with the firm belief that they are based 

 upon fundamental principles and experimental data; and incidentally 

 to emphasize the need of some new method which will indicate definitely 

 and accuratel}' the true lime requirement of soils. 



In employing the freezing point method to measure the concentration 

 of the soil solution directly in the soil; the effect of the application of 

 fertilizers upon the concentration of the soil solution* ; the concentration 

 of the cell sap directly in the plant tissue^ ; and the effects of biological 

 activities directly in the soil*', the idea occurred that the freezing point 

 method might also be employed to determine or study both the nature of 

 soil acidity and the lime requirement of soils. It Avas reasoned that if 

 the soil contains a free soluble acid, this acid would possess a definite 

 freezing point depression at a certain concentration. Upon titrating this 

 acid with a base, such as Ca(0H)2, a salt would be formed. This salt 

 would probably possess a different freezing point depression from that 

 of either of the reacting agents. The depression then should vary as 

 more and more of the lime is added to the soil until the neutralization 

 point is reached where the formation of the salt is completed and then 

 the direction of the depression should change. If on the other hand, the 

 soil does not contain a free soluble acid but possesses an absorptive 

 power for lime, due to its unsaturated or unsatisfied silicate compounds 

 and organic matter, then the depression of the freezing point of the soil 

 should remain the same as more and more lime is added until these sili- 

 cate compounds and organic matter are satisfied with the base, and then 

 it should increase with further addition of Ca(0H)2. Finally, if the 

 soil is alkaline or already saturated with bases, then the depression 

 should begin to rise immediately upon adding a small amount of Ca (OH) 2 

 to the soil. 



Happily all these a priori predictions were actually and experimentally 

 realized in soils exactly as they are described above. 



The freezing point method then promises of being capable to perform 

 three functions simultaneously: (1) to indicate whether or not a soil 

 needs lime, (2) the quantity it requires, and (3) the nature of its acidity. 



(4) Tech. Bui. 24, 1915, Mich. Expt. Sta. 



(5) J. Am. Soc. Agr. 8, 1916. 



(6) Science, 44, 65, 1916. 



