Relations of Higher Plants to the Formation of Nitrates 83 



32 these values are given, and also the figures for the nitrates formed by 

 incubation with dried blood less those formed by direct incubation, which 

 probably also represent the efl&ciency of the nitrate-forming bacteria. 



The method used in measuring the nitrate-forming activity of the soil 

 was as follows: The soil was sampled by means of a soil auger to a depth 

 of eight inches. The borings from the plat or section of plat to be tested 

 were mixed, quartered, and placed in an air-tight jar while still moist. 

 When the jar was brought to the laboratory, moisture and nitrates were 

 determined within twelve hours after sampling. Nitrates were deter- 

 mined in 100 grams of moist soil by means of the disulfonic-acid method. 

 Another 100 grams of moist soil was placed in a bottle having a capacity of 

 250 cubic centimeters, and sufficient water was added to bring the moisture 

 content to 25 per cent of the dry weight of the soil. A loose cotton plug 

 was inserted into the mouth of the bottle, which was then placed in an 

 incubator and kept at a temperature of 30° C. and at a constant moisture 

 content for fourteen days, at the end of which time nitrates were deter- 

 mined. Tests were made also by adding 100 milligrams of dried blood to 

 100 grams of fresh soil and incubating as above. The samples of soil 

 for tests with dried blood and those for tests without dried blood were 

 weighed out at the same time, so that the conditions of the test were 

 similar except for the addition of the dried blood. 



TABLE 32. 



Nitrate Formation in Planted and TJnplanted Soil Incubated with 

 AND without Dried Blood, in 1911 (Farts per Million) 



Plat 



Crop aad treatment 



Nitrates in natural soil 

 less field nitrates 



June 

 16 



July 

 10 



October 



Nitrates in soil 



plus dried 



blood, less 



field nitrates 



June 

 16 



July 

 10 



Nitrates in soil plus 



dried blood, less nitrates 



from incubation with 



natural soil 



June 

 16 



July 

 10 



78 



96 



93 



88 



79 



85 



100 



82 



59 



75 



61 



74 



August 



4 



2201, 

 2401, 

 2201, 

 2401, 

 2203, 

 2403, 

 2203, 

 2433, 

 2207, 

 2407, 

 2207, 

 2407, 



2209 

 2409 

 2209 

 2409 

 2211 

 2411 

 2211 

 2411 

 2215 

 2415 

 2215 

 2415 



Maize, mulched . , 



None 



Maize, cultivated 



None 



Oats 



/ None 



110 

 126 

 119 

 139 

 105 

 118 



142 

 125 

 141 

 127 

 115 

 111 



51 

 50 



