20 
BULLETIN 6 2, HAWAII EXPERIMENT STATION 
In a discussion of these results, the very good parallelism between 
the various moisture coefficients is probably the most striking fact. 
This is not at all surprising when one considers that while the differ- 
ent forms of water in the soil are held by different physical forces or 
different combinations of such forces, the factors determining the 
magnitude of these forces are the same in every instance, namely, 
texture and organic matter. These two factors exert their influence 
in varying degrees and proportions. From a textural point of view 
the amount of moisture adsorbed or held depends on the surface ex- 
posed, and for this reason soils containing 
large amounts of fine 
70 
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X 
20 
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YMffl/A *>£& C£A/T 0/=- C0LLO/0S 
' ' JK4TS/2. H>?f>0G s40&0je&£0 
mi...is»w-a />£& C£/VT 0£ 0/e&J?WC Af*47~T£/Z 
/2 2/ 
3/ 27 *2 *S 
&0/L A/0. 
S6 S7 6S 66 69 76 
Figure 9. — Relation between per cent colloids, per cent organic matter, and per cent 
water vapor adsorbed 
matter or colloids adsorb or hold much more moisture than soils con- 
taining small amounts of such matter. The same relationship exists 
between organic matter and moisture held or adsorbed. Further- 
more, since usually all the organic matter is a part of the colloidal 
fraction on the basis of particle size, it may be said with a good de- 
gree of accuracy that the moisture properties of soils depend on the 
colloidal fraction — organic and inorganic. 
To permit study of the relationship between organic-matter con- 
tent, colloidal content as determined by mechanical analysis, and 
moisture properties of soils, these three factors were plotted in Figure 
9. The surprising feature of this diagram is that the hygroscopic 
moisture not only does not follow the colloid content but in the larger 
number of cases there is an inverse relationship. However, the hygro- 
scopic moisture conforms more or less to the per cent organic matter. 
