550 The Storage of Farmyard Manure 



are aerobic. As soon as the oxygen is used up in any particular portion, 

 the conditions become anaerobic, and compounds formed under the 

 previous aerobic conditions may decompose. When,vOwing to change 

 of temperature, or other conditions, more air diffuses into this portion, 

 the conditions again become aerobic, and compounds formed under 

 the anaerobic conditions may decompose. Thus we have a perpetual 

 succession of decompositions so long as the conditions fluctuate between 

 aerobic and anaerobic 



It will be seen that nitrification and denitrification form a particular 

 case of this hypothesis. We prefer the general form because other 

 reactions of the sort are by no means out of the question. 



The conversion of ammonia into complex nitrogen compounds. 



Reference has already been made (p. 504) to the claim set up by 

 Maercker and Schneidewind that the amount of quick-acting nitrogen 

 (i.e. ammonia and amide) in the manure is considerably less than the 

 digestible nitrogen in the food, while conversely the amount of slow- 

 acting nitrogen in the manure is much greater than that of the indi- 

 gestible nitrogen of the food. Some of their results are : 



Indigestible N N as other 



Well trodden dung (deep stall) . 

 Dung kept in covered shed 

 „ ,, the open 



They therefore supposed that a considerable conversion of ammonia 

 and amide into complex nitrogen took place during the making of the 

 manure, and they attributed this to microorganisms. 



Unfortunately their figures are not entirely experimental, the values 

 for the digestibility of the foods, litter, etc., being assumed, and not 

 determined directly. Russell and Goodwin^ were unable to obtain 

 such high numbers. Assuming mean values for the digestibility of the 

 food stuffs their results came out much lower: 



1 Journ. South-Eastern Agric. Coll. Wye, 1905, No. 14, 187. 



