Fertilizer Treatment 303 
TABLE 6. 
Nitrates After Two Weeks Inzubation. 
(Parts per million calculated on a Dry Basis) 
Plot 
Total) 292.90 | 365.20 | 482.5: 
Ave..| 22.53 | 28.09 | 37.1% 
difrered from the fresh nitrate test in that moisture content was con- 
trolled and there was no loss of nitrates from crop growth or leaching. 
Table No. 4 shows that the nitrate content of the soils was high 
for May and July, medium for April, low for March, June and Novem- 
ber and very low for August, September and October. 
The manure plots, Nos. 2 and 3, were high for March, April, and 
November. The averages of these plots for the period were about 
equal and much above the average of all plots. 
The three plots 4, 6, and 8 receiving nitrogen in addition to phos- 
phorus or potassium or both had an average nitrate content of 27.63 
for the period. The average nitrate content was 23.79 for plots 7, 10, 
and 12 which received the same treatments except the nitrogen was 
left out. 
The average of the three check plots 5, 9, and 13, was 25.07 for 
the period. The check plots in this case were slightly higher in nitrate 
content than the plots receiving either phosphorus or potassium or both. 
This difference was not marked but it may have been caused by a 
greater lack of nitrogen in the treated soil due to a larger crop growth. 
However, the average of the untreated plots was also higher than the 
plot receiving only the nitrogen treatment. The average of the plots 
7, 10, and 12 which had no nitrogen in their treatments was slightly 
higher than the average for the N plot No. 11. 
The increase in nitrate content of the incubated samples over that 
of the fresh soil samples was proportionately much less when the fresh 
nitrates were low as in June and October. The average on both tests 
was highest for the period in July. The July increase in nitrate con- 
tent after incubation was 350 per cent. But in October the increase 
with incubation was only 15.9 per cent. The increase for the high 
month of July was 62.33 parts but the increase for the low month of 
June was only 16.08 parts. 
It then would seem in this instance that periods of low nitrate con- 
tent may indicate times of low nitrifying power of a soil. The results 
