The Composition and Use of Fertilizers. 243 



large proportions of nitrogen escape as ammonia. If, however, 

 the manure is too compact, the fermentation may he so slow as not 

 to decompose the manure enough for its most effective use in the 

 soil. 



The amount of moisture in manure is an important factor in 

 controlling the rapidity of fermentation. The addition of water 

 causes reduction of temperature and a corresponding slowness of 

 fermentation. Water, when added in sufficient quantities, also 

 fills up the pores of the Heap and serves to exclude air, thus retard- 

 ing the most active form of fermentation. 



Manures which are rich in soluble nitrogen decompose more 

 readily than others which contain less soluble nitrogen. Thus 

 urine decomposes much more rapidly than solid excrement. 



Changes Produced by Fermentation. — The principal changes 

 that take place in the more common methods of fermentation or 

 " rotting " of manure may be briefly outlined as follows: (1) The 

 carbon of the manure combines, to a greater or less extent, with 

 the oxygen of the air, forming carbon dioxide (carbonic acid gas), 

 which escapes into the air. (2) The nitrogen combines with hy- 

 drogen to form ammonia. If the manure heap is dry, the am- 

 monia combines with carbon dioxide, forming ammonium carbon- 

 ate, which may escape into the air and be lost to the manure. If 

 the heap is kept moist, certain organic acids are formed by the 

 decomposition of the organic matter, and the ammonia, as fast as 

 it is formed, unites with these acids, producing ammonia salts 

 which readily dissolve in water, but which do not escape as gases 

 into the air. (3) Considerable water is driven off from the ma- 

 nure by the heat which is produced in the process of fermentation. 

 (4) In the inner part of the heap, which is shut off from the air, 

 there is serious danger that nitrate-destroying germs will decom- 

 pose the nitrates and thus cause their loss. 



Difference between Frcsli and Fermented Stable Manure. — 

 From the foregoing it would follow that fresh stable manure dif- 

 fers from fermented or " rotted " stable manure in the following 

 respects: The fresh manure contains (1) more water, and (2) more 

 carbon than the fermented manure; while (3) both contain in their 

 dry matter the same amount of potash, phosphoric acid and nitro- 

 gen, provided the process has been carefully managed. In 

 " rotted " manure, (4) the nitrogen is in a more available form 

 as plant food; the same is also true of the potash and phosphoric 

 acid. (5) If the process of rotting is allowed to go too far the 

 nitrates will be changed into free nitrogen and lost. 



Between two and three tons of fresh mixed stable manure are 



