586 



STATE BOARD OF AGRICULTURE. 



DETERMINING THE WILTING COEFFICIENT OF SOILS BY THE FREEZING POINT 



METHOD. 



It has already been mentioned that solidification cannot be started, 

 at least very readily, below a certain moisture content. The i)ercentage 

 of this moisture content is quite definite and very different in the diverse 

 classes of soil. It occurred to us that this point of water content where 

 solidification refuses to take place might be the same as that where 

 plants begin to wilt. In order to obtain information upon this interest- 

 ing ])hase of the investigation the Avilting coefficient of several soils was 

 determined by following the method described by Briggs and Shantz 

 (16), and using wheat as indicator. Several series of experiments were 

 performed upon the subject. The results of one series which are typical 

 of all the results, are shown in Table 11. In this table there are pre- 

 sented also the moisture contents at which solidification refuses to take 

 place or at least very readily. 



Table 11 



Comparison of the Moisture Content of Soils where Solidification Refuses to Take Place and 



where Plants Begin to Wilt. 



Nane of soil. 



Percentage of 



water where 



solidification 



refuses to 



take place. 



Percentage of 



water where 



plants begin 



to wilt. 



Sand 



Sand loam 



Silt loam 



Heavy silt loam 

 Heavy silt loam 

 Heavy silt loam 

 Sandy loam . . . . 



2.10 

 6.7 

 10.3 

 16.8 

 16.00 

 13.50 

 5.60 



1.49 



5.28 



9.62 



18.79 



17.16 



13.82 



4.87 



By comparing the two columns it will at once be seen that the 

 percentage of water content at which wilting of the plants occurred 

 and the solidification refused to take place, agree remarkably. It will be 

 noticed that in no case does the difference exceed more than 2%. 



We confidently believe that the point where solidification refuses to 

 take place marks an important transition in the state of the soil mois- 

 ture and that this point is very close to the wilting coefficient of soils. 

 Hence, we further believe that the freezing point method can be used to 

 determine the wilting coefficient of soils and that such determinations 

 will be more accurate and of course infinitely more convenient and rapid. 



(16) Loc. cit. 



