sept. 4 . 1916 Influence of Barnyard Manure on Soil Bacteria 



913 



If the average number of bacteria found in the manured soil be taken 

 as 100 per cent, the soil receiving 5 tons of manure then becomes 123 

 per cent and that receiving 15 tons, 129 per cent. Taking the average 

 bacterial count of the plot receiving no irrigation water as 100 per cent, 

 the others then become with 5 inches of water, 109 per cent; with 10 

 inches of water, 104 per cent; with 20 inches, 103 per cent; with 30 

 inches, 94 per cent; and with 40 inches, 112 per cent. With one excep- 

 tion the irrigation water had increased the number of bacteria in the soil. 



The same plots were analyzed on the same dates for their ammonify- 

 ing powers, and the results are given in Table VIII as milligrams of 

 ammonia produced in four days in 100 gm. of soil, to which were added 

 2 gm. of dried blood. Each result is the average of a number of closely 

 agreeing determinations. 



Table; VIII. — Quantity of ammonia (in milligrams) formed in four days in 100 gm. of soil 

 containing 2 gm. of dried blood — cropped plots 



Number 

 of deter- 

 minations. 



6 

 6 

 6 

 6 

 6 

 6 

 6 

 6 

 6 



6 



6 



6 



6 



6 

 6 



6 



6 

 6 



Treatment. 



No water; no manure 



5 inches of water; no manure. . 

 io inches of water; no manure . 

 20 inches of water; no manure . 

 30 inches of water; no manure . 

 40 inches of water; no manure. 

 No water; 5 tons of manure .... 

 No water; 15 tons of manure . . . 

 5 inches of water; 5 tons of 



manure 



5 inches of water; 15 tons of 



manure 



10 inches of water; 5 tons of 



manure 



10 inches of water; 15 tons of 



manure 



20 inches of water; 5 tons of 



manure 



20 inches of water; 15 tons of 



manure 



30 inches of water; 5 tons of 



manure : 



30 inches of water; 15 tons of 



manure 



40 inches of water; 5 tons of 



manure 



40 inches of water; 15 tons of 



manure 



Quantity 01 ammonia. 



May 10. 



54-05 

 48.96 

 50. IO 



53-04 

 48. 96 



52.87 

 57.80 

 71.69 



60.33 



91.63 



61.08 



92.99 



63.16 



96. 69 



57-97 

 97.41 

 63.07 

 86.87 



Nov. 8. 



46.59 

 45-73 

 44- 54 

 39-95 

 36.89 



37-07 



55- 2 5 

 68.85 



53- !7 

 73-79 

 61.54 

 87.05 

 56. 10 



89-45 

 5i-34 

 76. 16 



77. 20 



Average. 



48.39 

 48. 11 

 48.60 

 47.09 



43-63 

 47. 16 

 60. 07 

 69.23 



58.06 



79-94 

 64.44 

 89.99 

 60. 26 

 95-76 



59. 16 

 96. 26 



60. 52 

 85-23 



The ammonifying powers of these soils are lower, as an average, in the 

 cropped than in the fallow soil. The average quantity of ammonia 

 produced by the fallow soil was 79.43 mgm., while that produced by the 

 cropped soil was 64.48 mgm. The variation due to seasonal differences 

 is not as great in the cropped as in the fallow soil, thus indicating that 

 the influence of the season on the rate of ammonification is greatly offset 



