344 ANNUAL REPORT OF THE Off. Doc. 



but it will hasten the ammoniacal fermentation so rapidly that 

 nitritication will soon cease. 



Both ammonilication and nitrification can be made active in a 

 manure heap, when not too closely compacted, or in a soil freshly 

 and heavily dressed with manure, by the use of plaster. Plaster acts 

 by decomposing the excess of ammonium carbonate as fast as formed, 

 producing in turn non-volatile ammonium sulphate, and calcium 

 carbonate (chalk); the latter compound serving as a mild base whose 

 presence is favorable to nitrification. 



The loss of ammonia from manure piles is not considerable as long 

 as the latter are kept moist or well compacted. When manure be- 

 comes dry, or when the latter is forked over or otherwise kept too 

 loose, a considerable loss of ammonia will result. So far as the 

 loss of ammonia alone is concerned, the application of plaster 

 may not be necessary, but if the latter be spread over the pile 

 with each considerable addition of manure from the stable, 

 its presence w'ill materially aid in the ammouification and nitrifi- 

 cation of the same and make it a more active stimulant when applied 

 to the land. 



Temperature of the Soil. 



Experience at Rothamsted in England shows that nitrification 

 takes place quite freely in the soil during an ordinary English 

 winter. Warrington^^ in one series of laboratory experiments showed 

 a considerable rate of nitrification in solutions kept at the tempera- 

 ture of 37 and 39 degrees F. 



According to Schlosing and Miintz, nitrification becomes active 

 at 54 degrees F. and rapidly increases up to 99 degrees F., at which 

 point it is nearly ten times as rapid as at 54 degrees. Above 99 de- 

 grees the rate of nitrification rapidly diminishes; at 122 degrees F., 

 very little nitrate is produced, and at 131 degrees F., it ceases en- 

 tirely. 



The Physical Condition of the Soil. 



Schlosing has shown that nitrification and microbic combustion 

 in general are less active in fine-grained compact soils than in lighter 

 coarse-grained soils. 



A certain proportion of clay and sand appears to be most favor- 

 able for a maximum rate of oxidation. In the experiment of Schlos- 

 ing equal amounts of ammonium sulphate were applied to equal quan- 

 tities of artificial soil in pots, and the nitrates determined at the end 

 of certain periods; from this the percentage of the ammonium salt 

 which was converted into nitric acid was determined as given in the 

 following table: 



