344 
Journal of Agricultural Research 
Vol. VIII, No. 9 
was small. This last is most notable in the first and again in the middle 
to lower depths of sampling. The cropped plots averaged 16.4 p. p. m. 
and the fallow 40.6 p. p. m. of sodium nitrate. 
Averages eor the Fate Seasons oe 1913, 1914, and 1915 
TOTAL SOLUBLE SALTS IN CROPPED SOIL 
From Table I and figure 9, which show the total soluble salts found 
in the cropped plots to a depth of 10 feet about the first of September, 
just after the com crop had been removed, we find that with a slight 
exception on the lands receiving 10 inches of water, manuring with 5 
tons per acre resulted in a lower salt content than with no manure. 
This difference is most marked with no and 5 inches of water applied, 
Fig. 9.—Graph showing the total soluble salts in the fall in cropped soil receiving different quantities 
of manure and irrigation water. Average of 3 years to a depth of 10 feet. 
and with io, 30, and 40 inches is hardly noticeable. In depth, although 
there are quite a number of exceptions for the individual feet in the 
irrigation treatments, the average shows a difference in total salts 
favoring no manure. The greatest variation is at the fifth, sixth, and 
seventh feet, and least at the first and ninth feet. 
Plots receiving 15 tons of manure showed less total salts for every 
irrigation treatment than those receiving none. The lower feet of the 
plots receiving these two treatments show more variation than the 
upper ones. 
It is mainly for no water and 5 inches, and the first, second, third, 
and sixth feet in depth that the averages for the 15-ton plots exceed the 
5-ton plots. 
The salts of the cropped soil receiving no manure tend to vary in¬ 
versely with the water applied; with 5 tons practically no regular varia¬ 
tion is shown, while 15 tons indicates an irregular variation inversely 
with the water applied. The average for all manuring treatments, 
