No. 4.] NlTllOGEN AND FERTILITY. 185 



exposed to the air in thin layers, which would seem to indi- 

 cate the desirabiUty of getting the applied manure under the 

 ground as speedily as practicalile, to avoid the loss from 

 washings by rain as well as from the fermentations, which 

 proceed very rapidly under these conditions. It is not ad- 

 vantag-eous to have nitric nitroo;en formed a great while 

 before the manure is to be used, because of the danger that 

 denitrifying bacteria will break up this nitric acid into free 

 nitrogen, and it be lost to plant life. This is another ad- 

 vantage in keeping the manure compact in a heap before it 

 is to be used. 



The Value of Farm Manure. 



The application of farm manures is advantageous from 

 two wholly different reasons. They carry considerable 

 quantities of plant food, particularly nitrogen. This is the 

 chemical side, which has been in the past perhaps unduly 

 emphasized. There is anotlier equal and in some cases 

 greater advantage derived from the application of farm 

 manures, because of the large amount of nitrifying bacteria 

 which they carry to the soil. 



It seems, from all of these considerations, that the twen- 

 tieth century farmers before the century is far advanced may 

 come to place as much dependence upon bacteria and the 

 fermentations which they produce, both in manure and in 

 soil, as upon the stores of plant food which the manure and 

 the soils contain. 



Summary. 



I have tried, in this somewhat hurried way, to outline 

 some of the changes that are going on in the knowledge of 

 the soil fertility in its relation to the supply of nitrogen. I 

 thank you for the patient hearing which you have given to 

 these somewhat dry, and I was about to add uninteresting, 

 facts. But the facts are not uninteresting. I wish I was 

 as sure as to the way they have been presented. In closing, 

 I wish to attempt to indicate some of the ways in w^hich 

 these facts can be utilized in practice. Much is yet un- 

 known on this subject, and no hard-and-fast statements can 

 be made. 



