350 
Journal of Agricultural Research 
Vol. VIII, No. 9 
NITRATES IN FALLOW SOIL 
A consideration of the nitrates found in fallow land, as given in Table 
IV and figure 12, wilfcshow that, except for the plots receiving no water, 
larger amounts were found in the soils on which an application of 5 
tons of manure was made than where no manure was added. With 
10 inches of water as an irrigation, the nitrates in the plots receiving 
5 tons of manure were double those in the unmanured plots, and more 
than double with 30 inches of irrigation water. Although the nitrates 
in the soils receiving no manure and 5 tons differ quite uniformly with 
regard to depth, each of the first 3 feet of the manured plots contained 
proportionately more than the unmanured. 
70 
No M anure 
5Tons Manure 
15Ton$ Manure 
i 
M 
1 
| 11 
Wcit er 
Applie d] None | 5 In. | loin. | 20 In. | 30 In. ■) 40 In. | 
Fig. 12.—Graph showing the nitrates in the fall in fallow soil receiving different quantities of manure and 
irrigation water. Average of 3 years to a depth of 10 feet. 
The soil receiving 15 tons of manure contained, on the average, 5 
p. p. m. of nitrates more than did that receiving no manure. This 
difference was greater for the plots receiving o and 5 inches of water 
than for those receiving more water, and also greater in the upper 2 feet 
than below this depth. 
With no water and with irrigations of 5 inches, the plots on which 15 
tons of manure were applied each contained more than twice as high 
nitrates as did the plots with 5 tons, although with 10, 30, and 40 inches 
of water the 5-ton applications were better than the 15-ton. The average 
differences in nitrates between these treatments are a little greater in 
the first 2 feet than deeper, although the lower 5 feet also show quite a 
pronounced influence. 
As with the cropped plots receiving no manure and 15 tons, the fallow 
indicates a tendency for the nitrates to decrease with increasing appli¬ 
cations of water, while the land receiving 5 tons of manure shows an 
increase in nitrates until 10 inches of water are applied before the de- 
