GERMAN AGRICULTURAL EXPERIMENT STATIONS. 209 



on the causes of this loss have already shown that it is not due to the 

 volatilization of the ammonium carbonate of the manure alone, but 

 also to the action of microorganisms which decompose nitrates (deni- 

 trification). The investigations especially of Professor Wagner in 

 Darmstadt have made important contributions to this subject. As a 

 result of these observations the agricultural experiment stations have 

 commenced to study the problems relating to barnyard manure from 

 the bacteriological side. From what has already been learned of the 

 part played by microorganisms, it is evident that the problems can not 

 be solved by purely chemical means. 



The investigations of Stutzer and Burri, of the agricultural experi- 

 ment station at Bonn, are also along this line, and have already resulted 

 in important contributions on the activity and the life conditions of the 

 microorganisms which decompose manures. This work requires con- 

 firmation and should be extended. 



The agricultural experiment stations will necessarily undertake the 

 bacteriologica. study of these problems on a large scale, and must add 

 bacteriologists to their permanent working force. These can also be 

 utilized in other lines of inquiry. 



The experiment stations are also conducting chemical studies on the 

 losses from barnyard manures with a view to preventing the loss of 

 nitrogen as far as possible by preservatives. In this line also note- 

 worthy results have been obtained by agricultural chemists, especially 

 through the aid of the German Agricultural Society. 



The results which are being obtained and the interest manifested by 

 the stations in the subject give encouragement that in the near future 

 the questions relating to barnyard manure will be fully solved. 



An indispensable aid to the investigation of the agricultural chemist 

 in this field of inquiry as well as in all others relating to fertilizers, are 

 vegetation experiments. These were first employed on an extensive 

 scale by Professor Wagner, of Darmstadt. By means of vegetation 

 experiments, carried on in suitable pots, partly out of doors and partly 

 in greenhouses, the indications from laboratory investigations are tested 

 under well-defined conditions. As an example of this it may be men- 

 tioned that the Halle experiment station found in its investigations 

 on barnyard manure that the efficiency of the manure did not always 

 correspond to what would be expected from its chemical composition, 

 i. e., the nitrogen compounds found by chemical analysis. The question 

 of the action of nitrifying organisms comes into account and this can 

 only be solved by vegetation experiments. 



For these reasons many German experiment stations are at present 

 providing themselves with vegetation houses, in order to take up the 

 most extended research in this line. Vegetation experiments are of 

 course not merely suited to studying the nitrogen nutrition of plants 

 but can also be used in solving other problems in manuring. Formerly 

 it was necessary to conduct very tedious field experiments, involving 

 many sources of error, in order to determine the efficiency of an arti- 



