2l6 



Journal of Agricultural Research 



Vol. XIII, No. 4 



sterilized, a small quantity was poured into a sterile container, and the 

 desired amount was drawn off in a sterile pipette graduated to o.oi c. c. 

 The solution was mixed with enough sterile water to make the soil up 

 to optimum moisture content, and the liquid was thoroughly mixed 

 through the soil with a sterile spatula. The samples were incubated 

 for four days at 29° to 30° C. and then distilled from copper flasks with 

 magnesium oxid in the usual way. The data presented represent the 

 average of three or more determinations which agree within 12 per cent 

 and with a few exceptions within 10 per cent. 



The freezing-point determinations were made by mixing 25 gm. of 

 soil with a proportional amount of solution, after which the mixture was 

 placed in a freezing tube and the freezing point determined with a Beck- 

 man thermometer. The data given represent the average of two deter- 

 minations. 



The following tables (I-VII) show the amount of the salt added, the 

 nitrogen produced from 2 gm. of dried blood, the depression of the 

 freezing point of the soil solution, and the corresponding osmotic pressure. 



While working with the sandy loam, it became apparent to the writer 

 that the increments by which the amounts of the salt used in the various 

 tests increased were much smaller than necessary to bring out the points 

 desired, and consequently some of the concentrations were omitted in 

 the clay-loam series. 



TabIvE I. — Ammonification of dried blood in sandy loam and clay loam with varying 

 percentages of magnesium sulphate 



Salt in air-dry soil. 



Per cent 



3. 000 



. 001 



. 002 



.008 



. 016 



•032 



. 064 



. 100 



. 200 



•300 



. 400 



• 500 



. 600 



. 700 



Sandy loam. 



Nitrogen 

 produced. 



Mgm. 

 75-70 

 69. 67 

 71.91 

 76. 12 

 77-38 



76. 54 

 68.97 



67- 57 

 61.87 

 62. 67 

 68.41 

 69. 25 

 61. 41 

 54.82 



Depression 



of freezing 



point. 



C. 



285 

 289 



275 

 280 

 308 

 280 

 32>° 



403 

 462 



530 

 568 

 610 



725 



Osmotic 

 pressure. 



A tmos- 

 pheres. 



3-435 

 3-483 

 3-315 

 3-375 

 3-712 



3-375 

 3-978 

 4.014 



4-857 

 5-567 

 6.386 

 6.843 

 7-349 

 8-732 



Clay loam. 



Nitrogen 

 produced. 



Mgm. 

 52. 10 

 56-36 



58.60 

 56-36 



57.20 



53-84 

 52.02 



49.64 

 44.87 

 48.52 



Depression 



of freezing 



point. 



•c. 



o. 276 



, 290 



315 

 28S 

 308 

 303 



373 



455 

 483 



Osmotic 

 pressure. 



Atmos- 

 pheres. 



3-327 

 3-471 



3-496 



3-797 

 3-471 

 3-712 

 3-652 



4-495 



5-483 



5.820 



The data in Table I show that for sandy loam the addition of o.ooi 

 and 0.002 per cent of the salt resulted in a slightly lower ammonification 

 than the untreated sample. The differences, however, are within the 

 limits of experimental error. Concentrations of 0.008, 0.016, and 0.032 



