THE USE OF FRESH MANURE. 63 



is much less readily available to plants than has been 

 generally supposed. If the availability of the nitrogen of 

 nitrates be taken as 100, that of the nitrogen of well- 

 rotted manure was only 45 per cent. Kiihn has found, 

 on the other hand, that the nitrogen of fresh cattle dung 

 is very readily available. If the availability of the nitro- 

 gen of sulphate of ammonia be taken as 100, that of fresh 

 manure was 92 per cent. Wagner further observed that 

 fresh manure has a decided tendency to liberate the ni- 

 trogen of nitrates or of green manures, so "that the in- 

 crease of crops secured by the horse dung and nitrates, 

 etc., together, may be less than is produced by the ni- 

 trates, etc., alone." 



"It appears that soils, to which were added three grams 

 of nitrogen ; viz., two grams in form of fresh horse dung 

 and one gram in form of nitrate of soda, yielded a very 

 considerably smaller crop than the same soil to which 

 one gram of nitrate nitrogen was added without dung. 

 This, according to Wagner, is explained by the fact that 

 the microbes in the fresh dung expelled nitrogen in the 

 gaseous form, both from the dung itself and from the 

 nitrate, before vegetation could assimilate it. 



"While the horse dung applied in Wagner's trials was 

 fresh and the quantities were much larger than are ordi- 

 narily used in farm practice, yet the facts above cited 

 have a very important bearing on the use of fresh stable 

 manure and possibly on the value of composts, such as 

 are used for forcing-house soil, in which the proportion 

 of stable manure is approximately near to that which was 

 used in Wagner's tests, where a large loss of nitrogen was 

 observed. It might, therefore, happen that applications 

 of nitrates or other nitrogenous fertilizers to the soil of 

 the forcing-house would have no marked effect on the 

 crop, while nevertheless available nitrogen was deficient 

 and the crop suffering in consequence. This result might 

 at least be expected to follow the use of fresh manure 

 water. ' ' 



