272 
Journal of Agricultural Research 
Vol. XXI, No. 4 
however, and has not been found effective where the soil is very im¬ 
permeable and where it is not practicable to mix the salt thoroughly 
with the soil. 
It has been found in these experiments that calcium chlorid is more 
effective in penetrating a compact and impermeable soil than the weaker 
solutions of calcium sulphate. It has also proved effective in making 
such soils readily permeable to water, and this permeability is retained 
after the calcium chlorid is well leached out with pure water. 
In a preceding paragraph it was remarked that the injurious effects 
of sodium salts in irrigation water were minimized when calcium salts 
were also present in sufficient quantity. It may not be possible to state 
definitely what these proportions should be in all cases, as this may be 
conditioned somewhat by the character of the soil. It is clear, however, 
that a soil rich in lime is not proof against injury from the sodium salts 
carried in the irrigation water. 
The neutralizing effect of calcium in solution with sodium is shown in 
Table II. In this experiment the soil used was also from the Yuma 
Mesa, but from a field that had been irrigated for 25 years with muddy 
water from the Colorado River, so that it was rich in silt and clay. The 
sample used consisted of 50 gm. of dry soil placed in a funnel over a 
small filter paper. It was leached each time with 100 cc. of solution or 
water. This soil was first leached with a strong solution of calcium 
chlorid which was followed by distilled water. It was then leached with 
a solution of equal parts of M/10 sodium chlorid and M/20 calcium 
chlorid, which was again followed by several leachings with water. It 
was finally leached with a solution containing 75 parts of M/10 sodium 
chlorid and 25 parts M/20 calcium chlorid, followed by distilled water. 
The results given in Table II show that the percolation rate for the 
water leachings was little or not at all retarded when they followed the 
calcium chlorid or the mixture of equal parts of the chlorids of calcium 
and sodium. On the other hand, when the proportion of the sodium 
salt was much greater than that of the calcium the subsequent water 
leachings showed the same symptoms as when the pure sodium salt was 
used. In this case the symptoms were rather more pronounced than 
with the soil used for the leachings shown in Table I, probably because 
of the larger proportion of clay in the soil. 
From these results it seems probable that when irrigation water con¬ 
tains much more sodium than calcium its use may be followed by an 
appreciable hardening of the soil. Where the difference in the quantity 
of the two salts is not great or where the total quantity of the sodium 
is not large it may be practicable to prevent injury by the use of gypsum 
on the land. 
In order to test the effects of sodium and calcium salts on a soil that 
was known to be naturally almost impermeable, a sample was taken 
from a field on the Newlands project near Fallon, Nev. This soil is so 
hard and impermeable that it is practically unproductive, yet when it is 
