90S 



Journal of Agricultural Research 



Vol. VI, No. 23 



If we take the average quantity of ammonia produced in the unma- 

 nured soil as 100 per cent and compare this with that produced in the 

 manured soil, we find those soils receiving 5 tons of manure produce 147 

 per cent and those receiving 15 tons produce 188 per cent; or the average 

 increase per ton of manure applied is twice as great when 5 tons are ap- 

 plied as when three times that much is used. 



Considering the average of the soil receiving no irrigation water as 100 

 per cent, the others then become with 5 inches of water, 106 per cent; 

 with 10 inches of water, 117 per cent; 20 inches of water, 108 per cent; 

 30 inches of water, 106 per cent; and 40 inches of water, 108 per cent. 

 The greatest increase in ammonifying powers results from the application 

 of 10 inches of irrigation water. 



The nitrifying powers were determined as previously outlined, and the 

 results reported in Table VI represent milligrams of nitric nitrogen formed 

 during 21 days in 100 gm. of soil containing 2 gm. of dried blood. The 

 results as reported are the average in each case of a number of determi- 

 nations taken during two years. 



Table VI. — Quantity of nitric nitrogen {in milligrams) produced in 21 days in 100 gm. 

 of soil to which had been added. 2 gm. of dried blood — -fallow plots 



All of these results will appear low when compared with those obtained 

 by many other workers, who report their results as milligrams of nitrates 

 found. The nitrifying powers of all the soils are low in the spring, but 

 become much higher in midsummer and fall back in autumn to about 

 where they were in the spring. 



During the spring the nitrifying powers of the soil vary with the manure 

 applied. But the difference existing between the manured and unma- 

 nured soil in no case is great. The irrigation water which had been 



