19-21.] 



Artificial Farmyard Mam rk 



105 



From the study of the iiitei-relations between nitrogen 

 and straw, we have come to the eonchision that the amount of 

 nitrogen necessary for pronounced rotting, and the amount vhich 

 straw is capable of " fixing " in the form of ammonia are iden- 

 tical and that, in general, the figure varies only between 0.70 

 and 0.75 parts of nitrogen per 100 parts of dry straw. Within 

 these limits fermentation proceeds without loss of nitrogen, and 

 it is obvious that, except in so far as the nitrogen content of the 

 original straw varies, the final " stabilised " product obtained 

 when rotting has proceeded to the extent of 40 to 45 per cent, 

 of dry matter must Ukewise exhibit comparatively slight variaHon 

 in its nitrogen content. In our experiments the " stabilis.? 1 " 

 product obtained from the fermentation of straw under a vari-ty 

 of conditions possesses a nitrogen content of about 2 per cpiit. 

 calculated on the dry material. 



It thus becomes possible to estimate fairly accurately what the 

 nitrogen content of any particular sample of fermented straw 

 will be when rotting has proceeded to an appreciable extent. If, 

 for example, the nitrogen content of the original straw is equal 

 to 0.50 per cent., and we assume that the theoretical amount of 

 iammonia nitrogen, equal to 0.72 lb. of nitrogen for 

 100 lb. of straw, has been fixed, then, with a loss of 40 per' cent, 

 of dry matter during fermentation, the resultant rotted ^^traw 

 will contain (0.50 + 0.72) x 100 60 = 2.03 per cent, of 

 ori^anic nitrogen in the drv matter. An additional amount of 

 ammonia nitrogen would probably result in a portion remaining 

 as free ammonia w^hich, as indicated above, would be liable to 

 loss if the fermented straw were allowed to become dry. The 

 data thus obtained enable us to turn to the process of inducing 

 the fermentation of straw on a large scale, and are also capable 

 of appHcation to the conditions operating in the production of 

 ordinary farmyai-d manure. 



Suggested Method for the Preparation of Artificial Manure. * 

 — As regards large scale work, a number of factors hnw' lo l">e 

 taken into account which did not operate in the laboratory experi- 

 ments. Experience has shown that urea and ammonium car- 

 bonate are the most suitable carriers of nitrogen sinct^ tb.ey 

 ensure a favourable alkaline reaction, and lead to rapid 1)reak- 

 down. pi'ovided that thev are not pi-esent in large excess. 'L'hey 

 are. however, far too expensive at the present time to admit of 

 general use in farm work, although a reduction in the cost of 



* This process, as well as its application to the jiurilication of sewage, has 

 been cvcicl In- Letters Patent (Britisli Pat. No. ir)2:i*^7). 



