358 
Journal of Agricultural Research 
Vol. VIII, No. 9 
Under field conditions more nitrates were found in both cropped and 
fallow soils during the summer than just after the corn crop was har¬ 
vested. 
The nitrates of the fallow field soils averaged higher with a manur¬ 
ing of either 5 or 15 tons to the acre than with tio manure, but on the 
cropped soil, although the 15-ton application of manure resulted in 
more nitrates than no manure, the 5-ton did not. The fallow soil showed 
the effect of the manure on the nitrates more in the top 2 or 3 feet than 
at lower depths. 
The highest soluble-salt content of fallow soil was on plots manured 
at the rate of 5 tons to the acre; the lowest was on plots receiving 15 
tons. The corresponding high and low points in cropped soil were on 
plots receiving no manure and 5 tons to the acre, respectively. 
Unirrigated land contained more nitrates than irrigated on both 
cropped and uncropped plots. Increasing the irrigation water applied 
to the soil decreased its nitrate content. 
The total soluble salts in cropped plots decreased as the water applied 
increased and in fallow soil an application of 40 inches of water resulted 
in less salts than where no irrigation water was added. 
The treatment affected the salts more in the surface foot than at* 
greater depths with small irrigations, but when 20 inches of water or 
more were applied some of the salts seemed to have moved below 10 
feet in depth. 
Targe irrigations decreased the soluble salts in cropped more rapidly 
than it did in fallow soils. 
Manuring or irrigating the soil affected the nitrates relatively more 
than the total salts. 
In unmanured soil the nitrate content was about twice as great with 
a fallow as with a crop, and in manured, it was about three times as 
great. 
The ratio of total soluble salts to the quantity of sodium nitrate found 
in a cropped soil rose from 24.5 to 1 without irrigation to 37.5 to 1 
when 40 inches of water were used. The ratio in fallow soil increased 
from 8.9 to 1 with no irrigation water to 16.2 to 1 with 40 inches. 
The field results do not indicate a close relationship between the crop 
yield and the total soluble-salt or the nitrate content of the soil if the 
differences between cropped and fallow soils indicate the amounts of these 
substances which the crop used. 
After a consideration of both pot and field experiments, it is evident 
that the soluble salts and especially the nitrates are found in lower 
concentrations in soils receiving large quantities of irrigation water than 
in those receiving less water. This is probably due in part to the leach¬ 
ing action of the heavy irrigations as well as to the lower nitrification 
in the presence of excessive soil moisture. 
