4IO 



Journal of Agricultural Research 



Vol. X, No. 8 



RELATION OF WATER RETENTIVENESS TO MAXIMUM WATER CAPACITY 



A comparison of the maximum water 

 content of the moistened layer at the end 

 show how little significance this value has 

 retentiveness (Table XII). Even at the 

 moisture content is only from one-half to 

 in the case of soil B, which in a dry state 

 water. 



capacity with the moisture 

 of the first hour will serve to 

 as an expression of moisture 

 end of this short period, the 

 two-thirds this value, except 

 delays the penetration of the 



Table XII. — Relation of the maximum water capacity of the soils to their 'moisture content 



at the end of the first hour 



Soil. 



A 

 B 

 C. 

 D 

 E 

 F 

 G 

 H 



Maxi- 



mtun 



water 



capacity 



Per cent. 



65 

 60 



63 

 60, 



56 



49 



55 

 57 



Water content of moistened 

 layer at end of i hour. 



Experi- 

 ment I. 



Per cent. 

 38.8 

 50. 2 



29- 5 

 39-2 

 29.8 



33-8 

 28.6 

 28. 4 



Experi- 

 ment II. 



Per cent. 



Experi- 

 ment III, 



Per cent. 



37- o 

 43-6 

 32. 6 



40- 5 

 32. 5 

 31-4 

 2?- 5 

 27.9 



Soil. 



I. 

 J- 



K 

 L. 

 M 

 N 

 O 

 P. 



Maxi- 

 mum 

 water 

 capacity 



Per cent. 

 53-4 

 46.3 

 36.0 

 31. o 



34- 2 

 27. I 

 27. o 

 28.9 



Water content of moistened 

 layer at end of i hour. 



Experi- 

 ment I. 



Per cent. 



25-7 

 22.8 

 21. 8 

 16. 9 

 18.4 

 12.8 



II. 7 

 13.0 



Experi- | Experi- 

 ment II. mentlll 



RAPIDITY OF CHANGE OF MOISTURE CONTENT IN THE MOISTENED LAYER 



It is of interest to know the average moisture content of the moistened 

 layer at the end of the successive intervals. This is reported in the 

 second part of Table VIII, having been computed from the weight of 

 dry soil in the cylinders, the initial moisture content, the weight of the 

 added water, and the depth to which this had penetrated. These data 

 assume much more significance when reported as the ratio of the moisture 

 content to the hygroscopic coefficient as in the third part of the same 

 table. In some of the finer-textured soils at the end of the first hour 

 this ratio was as low as 3.0 to 3.2, while in some equally fine it was as 

 high as from 3.7 to 4.1. In the fine sandy loams it had not fallen below 

 4.2 to 7.2 at the end of the hour, while in the sands it was as high as 7.5 

 to 14.8. The fall in the ratio after the first hour was so rapid that at 

 the end of the first day it was between 2.0 and 3.0 in the case of the 

 soils with a hygroscopic coefficient above 5.5, and was between 2.9 and 

 5.0 for the group of soils with a coefficient of about 3.3. In all, however, 

 even in the coarsest soils, the decline was marked. During the follow- 

 ing four days the decline was slight, being greatest in the sands, as 

 shown in Table XIII. 



