IRRIGATION WATERS AND THEIR EFFECTS. 13 
water then leaves the potash in the soil. I cannot give the ratios 
between the water applied, the water in the soil and the amount 
of drainage. It would be much more satisfactory if I could, but 
we will have to content ourselves with comparing like volumes of 
water, the acre-foot. 
Another question suggests itself. What are these waters do¬ 
ing for us in regard to the salts that we do not want, beside the 
sodic carbonate which we have seen that they are removing? 
Their work in this line may be disappointing but still they are 
efficient and constant friends. We have seen that the water of one of 
our reservoirs, Terry lake, contained three tons of mineral matter per 
acre-foot, and we find that an acre-foot of drainage water which 
came from a pretty bad piece of land, carried July 23, 1900, 2,840 
pounds, a little less than half as much as the stored water and 
verv much less than the water within the soil, either after or be- 
fore irrigation. It is evident that the salts do not pass out of the 
soil into the drain water as easily as we would expect and yet they 
carry a large quantity when we calculate it for a year. 
The salts that the drain waters carry will vary some with the 
soil, but in our case we find them much more uniform than the 
salts carried by the waters while in the ground itself. The salts 
that we find in these waters are calcic sulfate, magnesic sulfate 
and the next one in the order of the quantity present is usually 
sodic carbonate. We have observed one instance in which the 
quantity of sodic sulfate present was greater than that of the sodic 
carbonate, but in this neither of these salts were present in large 
quantities. There was more sodic sulfate present in this sample, 
and much less sodic carbonate, than is usually found in drain 
waters. 
The salt removed in the largest quantity was found to be cal¬ 
cic sulfate. There is an abundance of this salt in the soil and 
under our conditions I imagine that it is a matter of indifference 
whether it is removed or not. The magnesia salts which came 
next in quantity in the drain waters also occurred abundantly in 
the soils, especially in those parts of our fields that were in the 
worst condition. I do not know whether these salts have any 
part in determining the mechanical condition of the soil or not, it 
is quite possible that they have, but I am unable to suggest just 
what that part may be. The presence of magnesic salts in very 
large quantities in certain ground waters, together with the fact 
that they are uniformly present, suggest that the series of changes 
taking place within the soil may end in the elimination of mag¬ 
nesic salts. I thought for a time that we might be able to find 
still other facts to support this suggestion, perhaps demonstrate 
that these salts are the last products in the series, but I have not 
found them and the suggestion seems of doubtful value. 
