68 NITRIFICATION AND DENITRIFICATION. 



may furnish this needed carbon, and the cellulose present in hay 

 or straw will also furnish it. Any form of decaying matter that 

 contains great amounts of hay or stubble is especially subject 

 to denitrification. Horse manure, containing as it does large 

 amounts of hay, shows greater losses of nitrogen than the manure 

 of cattle, which contains less carbonaceous material. 



The extent of the actual losses caused by these denitrifiers in 

 ordinary farm processes is not fully known. It is certain that in 

 concentrated decomposing solutions the action is vigorous, but 

 it is not so great in less concentrated masses. In the manure heap 

 there is always some loss in this way, and when great quantities 

 of manure are spread over a plot of cultivated ground, denitrifica- 

 tion doubtless causes considerable loss. When, however, the manure 

 is applied in limited quantity, so that it is mixed with a considerable 

 amount of soil, the evidence seems to show that the losses are slight 

 if any. In ordinary soil, therefore, denitrification is not a phenome- 

 non of much significance. In concentrated manures, however, 

 especially if they contain much hay, it may be great. One very 

 impoitant lesson is to be drawn from these facts. Nitrates should 

 never be mixed with manure. The nitrates will simply be thrown 

 away, since the denitrification in the manure heap will surely 

 reduce most of the nitrate to free nitrogen, thus causing its complete 

 loss. Further, the denitrification is greatest in fresh, concentrated 

 manure, while it diminishes greatly in manure after it has partly 

 decayed. The denitrifiers do not find the partly decomposed 

 organic substance favorable to their life, and do not flourish. Hence, 

 the use of large amounts of partly rotted manure upon a soil is 

 possible without bringing about a nitrogenous loss, while the use 

 of the same amount of fresh manure would be undesirable. 



