30 
Table XIV shows the effect of salts upon the hygroscopic power of 
soils. That this property should be affected by the addition of fer- 
tilizers was to be expected, since most salts possess this property 
themselves to a greater or less extent, and it is only natural that they 
should impart it to soils. These experiments were conducted by 
exposing a thin layer of soil to a saturated atmosphere in two large 
containers. Conditions were made as nearly similar as possible, but 
blank samples of soil were exposed in each as checks. Salts were 
well mixed with a bulk of soil at the rate of 0.5 per cent of salt, and 
weighings made from this bulk. Samples were exposed for 48 hours 
and total moisture determined in the air bath at 105° C. 
Table XIV. — Effect of salts and fertilizers on hygroscojpic moisture. 
Salts and fertilizers. 
Soil 
Sou 
Soil 
Soil 
No. 530. 
No. 573. 
No. 428. 
No. 516. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
3.17 
10.84 
9.87 
5.54 
17.21 
19.35 
14.80 
21.40 
16.78 
19.80 
14.05 
21.30 
16.76 
17.88 
13.90 
19.90 
17.08 
18.70 
15.53 
21.15 
17.28 
24.80 
17.45 
22.20 
17.64 
24.20 
15.80 
21.30 
16.35 
18.90 
14.55 
20.70 
16.26 
20.81 
13.70 
21.20 
16.90 
20.20 
14.70 
21.50 
16.56 
22.00 
15.08 
20.50 
17.07 
20.30 
13.80 
21.40 
16.50 
18.50 
14.35 
21.80 
18.95 
32.00 
22.02 
30.00 
16.35 
18.58 
14.58 
21.10 
Soil 
No. 542. 
Original moisture content of soils 
Potassium sulphate 
Calcium oxid 
Acid phosphate 
Ammonium sulphate 
Sodium nitrate 
Sodium carbonate 
Check 
Calcium sulphate 
2 (NH4)-14-2 1 
2(N03)-14-2i 
Superphosphate 
Potassium sulphate and acid phosphate. 
Sodium chlorid 
Check 
Per cent. 
4.12 
18.45 
16.10 
16.42 
20.30 
20.10 
17.95 
16.11 
17.30 
16.80 
17.06 
16.70 
16.60 
22.50 
16.18 
1 Fertilizer mixtures containing nitrogen, phosphoric acid, and potash in the order and proportions 
(percentages) named; nitrogen from ammonium sulphate in the first, from sodium nitrate in the second. 
The effect of adding salts upon the ferruginous clay is to increase 
the hygroscopic power in every instance, except where calcium sul- 
phate is added, in which case there is very little variation. As a 
matter of fact the general tendency of all the salts on the different 
types is to increase this property of soils, and in cases where there is 
a decrease it is almost negligible. Sodium chlorid, being itself a 
hygroscopic salt, imparts the highest absorbing power to the soil, 
while the lowest is effected by addition of acid phosphate. 
SUMMARY. 
The foregoing pages contain data obtained from an extensive study 
of the physical properties of Hawaiian soils and the effect of fertilizers 
upon these properties. It is evident that agents whioh influence the 
mechanical condition are many and complex. It has also been clearly 
demonstrated that the addition of salts or fertilizing materials affects 
the structure of the soil. 
It is impossible to predict in all cases the degree to which any one 
or all physical properties will be influenced by the addition of a fer- 
