458 
Journal of Agricultural Research 
Vol. VII, No. io 
lost more than the free-water surfaces. The deeper soils were also more 
uniformly wet. Capillarity doubtless played a part in. this experiment. 
Table VII .—Comparison of evaporation from large areas and shallow soil with small 
areas and deep soil, io kgm. of Greenville loam being used in each case 
Soil 
moisture. 
Shallow tanks. 
Deep cans. 
Surface 
area. 
Total 
evapora¬ 
tion. 
Evapora¬ 
tion 
for each 
square foot 
of surface. 
Surface 
area. 
Total 
evapora¬ 
tion. 
Evapora¬ 
tion 
for each 
square foot 
of surface. 
Per cent. 
5-4 
io. 4 
15-4 
20. 4 
25-4 
30-4 
35-4 
Sq.feet. 
5*42 
5* 42 
5- 42 
5- 42 
5*42 
5*42 
5* 42 
Gnt. 
2 , 935 
6,100 
7, 770 
7,405 
8,299 
8,41s 
8,98s 
Gw. 
542 
1,125 
1,434 
1,366 
1,531 
i> 5S3 
1,658 
Sq. feet. 
0. 66 
.66 
.66 
.66 
.66 
.66 
.66 
Gw. 
270 
440 
700 
920 
I, OIO 
995 
1,270 
Gw. 
409 
666 
1,066 
U395 
1,530 
1,500 
i,939 
SOLUBLE SALTS 
The effect of dissolved salts in reducing the vapor tension, and conse¬ 
quently the evaporation of solutions, is well known. The action of 
these salts in the soil on evaporation, however, is not so clear, since 
secondary factors may 
be introduced. In the 
ordinary agricultural 
soil the concentration 
of soluble salts is not 
sufficient to have any 
marked effect on 
evaporation, but in the 
alkali soils of arid re¬ 
gions salts may be pres¬ 
ent in sufficiently high 
concentrations to affect 
the loss of moisture 
materially. 
With a view to deter¬ 
mining some of the ef¬ 
fects of salts on evaporation, a number of experiments were conducted. 
In the first, solutions of sodium chlorid of various concentrations without 
soil were investigated. The solutions were placed in glass tumblers, two 
tumblers being used for each treatment, and set in the open laboratory 
where evaporation could go on freely. The tumblers were weighted every 
few days and the loss made up with distilled water. 
Fig. 16.—Evaporation from sand wet with distilled water and with 
sodium-nitrate solutions of differ ent concentrations. 
