Mar. i , 1924 
Movement of Water in Irrigated Soils 
655 
experiment just described, 10 per cent of water would be enough to sup¬ 
port plant growth. With this quantity of solution in the soil it is not 
unreasonable to assume that the actual quantity of dissolved material 
per unit of soil would be even less than is shown with 40 per cent of water, 
and this solution would contain a smaller proportion of both organic 
matter and carbonate. 
From other observations that have been made on solutions extracted 
from irrigated soils it seems probable that under ordinary field conditions 
the soil solution will only rarely show a reaction for normal carbonate, 
that is to say, will give a pink color with phenolphthalein. On the other 
hand, it is almost equally uncommon to find a saline soil containing 
appreciable quantities of sodium salts that does not show such a reaction 
when it has been leached with pure water. 
In the experiment just described the original sample of soil was sub¬ 
divided and each part was digested once with a certain quantity of water. 
This method of treatment is one that is used in making analysis of soils, 
but it does not correspond to anything that ordinarily goes on in the field. 
The second method of treatment referred to at the beginning of this 
chapter bears some resemblance to the process of reclaiming a saline soil 
by repeated copious irrigations. 
According to this second method of treatment, a large sample of soil, 
3 kgm., was saturated with "water, 900 cc., and the mixture was kept 
in a closed jar for 24 hours with repeated shaking. After 24 hours a 
part of the solution, 120 cc., was withdrawn by means of a suction filter, 
and an equal quantity of distilled water was again added to the soil. In 
this way a portion of the dissolved material was removed with each 
sample of the solution, and with each withdrawal and replacement the 
solution became more dilute. 
The soil used in the present experiment was of the same type as that 
used in the previous experiment, though it showed somewhat less soluble 
material. The extracted solutions again showed only traces of calcium 
and magnesium, so that these elements were not determined quantita¬ 
tively. The analytical methods used were the same as those used in the 
previous experiments . 11 The analytical results of this dilution experiment 
are shown in Table XIX. The total solids are given as percentages of 
the original soil and the constituents as percentages of the total solids. 
The successive withdrawals of the solution resulted in the gradual 
reduction of its concentration. This reduction in concentration was ac¬ 
companied by a change in the proportions of the constituents, as shown 
in the table, and also by a change in the physical character of the wet soil. 
It was observed that while the first withdrawals were made without 
difficulty the later ones were harder to get out, so that after the fourteenth 
extract the experiment had to be discontinued because the solution could 
no longer be obtained. 
In this experiment, as in the preceding one, it was found that as the soil 
solution became more dilute the proportion of dissolved oragnic matter 
and of carbonate increased while the proportion of the chlorin and the 
sulphate decreased. The character of the solution at the end of the 
experiment was very different from that at the beginning. This difference 
in the character of the solution was also reflected in a change in the 
physical character of the soil. 
11 This experiment was conducted by J. F. Breazeale, who also made the analyses. 
