Feb.26,1917 Effect of Water and Manure on Nitrates in Soils 357 
proportionately more for the nitrates than for the percentage moisture 
or total salts; the greatest effect of the crop on the moisture and total 
salts being felt on the plots which received 5 tons of manure, and for 
nitrates with 15 tons if we consider the difference in these factors between 
cropped and fallow plots to have all gone to the crop. The effect of the 
crop on the moisture content is more marked for no and 5 inches of 
water than for the larger amounts and is more for these quantities of 
water with 15 tons of manure than with the other manuring treatments. 
The difference between cropped and fallow plots for nitrates is greater, 
as an average, with no and 5 inches of water, the loss due to the crop 
being greatest for 15 tons of manure. 
In general, then, it may be said that, although cropping reduces the 
percentage of moisture, the total salts, and nitrates of the soil, the 
8 - 
Appl I ed<-L-i-—J-J- 
Fig. 18. —Graph showing the total yield of com stover and grain produced with different irrigation and 
manuring treatments. Average for three years. 
reduction does not seem to bear as close relationship to the crop yield 
as to the water and manure applied. More nitrates are formed with 
rather low percentages of water, and the plants seem to use more nitrate 
nitrogen where water is not plentiful than where more is given. 
SUMMARY 
Three distinct sets of experiments are reported in this paper. 
With a sod soil held in the laboratory for 2 y 2 years, the total salts and 
nitrates accumulated most rapidly with a moisture content between 
23 and 28 per cent. 
Cropped and uncropped soil kept in large tanks under controlled 
moisture conditions showed a decrease in nitrates and total soluble 
salts as the percentage of moisture increased, the nitrates being par¬ 
ticularly low in water-logged soil. 
