33 8 
Journal of Agricultural Research 
Vol. VIII, No. 9 
salts and nitrates to the full depth of the tanks. Each sample was 
thoroughly mixed before the analysis was made; hence, the figures rep¬ 
resent the average for the whole tank. There was a check tank for each 
treatment. 
CONSTANT-MOISTURE CONTENT 
The lowest moisture content was a little less than 15 per cent for the 
cropped and nearly 22 per cent for the fallow tanks, and the highest 
slightly over 35 per cent for both sets that were maintained at the same 
moisture content throughout the season. 
Figure 2 shows that the lowest moisture content favored the greatest 
accumulation of total soluble salts and nitrates in both the cropped and 
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Fig. 3.—Graph showing the total soluble salts, nitrates, and crop yields in tanks containing soil with 
varying moisture contents during different stages in the growth of the crop. 
the uncropped soils. For the cropped tanks containing between 20 and 
28 per cent of moisture (where the best crop growth was obtained) the 
total salts and nitrates, as compared with fallow, are especially low. 
The fallow tanks decreased in total salts from 874 parts per million at 
a moisture content of about 22 per cent to 235 p. p. m. at slightly over 35 
per cent. Corresponding to these moistures, the nitrates decreased from 
250.9 to 35.8 p. p. m. It will be noted that the ratio of total salts to 
nitrates is much larger for the cropped than for the fallow plots, showing 
that the plants take up nitrates faster than they do the other salts. 
VARIATION IN MOISTURE AT DIFFERENT STAGES 
Figure 3 shows the percentage moisture maintained in the second set 
of tanks for each stage in the growth of wheat, the total salts and 
