The bacteria which produce the most rapid fermentation in manure need plenty of air with its oxygen. Therefore fermentation will be more or less rapid according as the manure is piled loosely or in a close compact mass. A certain amount of moisture is necessary for the fermentation to take place, but if the manure is made quite wet the temperature is lowered and the fermentation is checked. The water also checks the fermentation by limiting the supply of air that can enter the pile. The composition of the manure influences the fermentation. The presence of considerable amounts of soluble nitrogen hastens the rapidity of the fermentation. Now when the manure ferments a large part of the organic matter in it is broken down and changed into gases. The gas formed most abundantly by the fermentation is carbonic acid gas, which is produced by the union of oxygen with carbon of the organic matter. The formation of this gas means a loss of humus. This loss can be noticed by the fact that the pile gradually becomes smaller. The next most abundant product of the fermentation is water vapor which can often be seen passing off in clouds of steam. When manure ferments rapidly the nitrogen in it is changed largely into ammonia. This ammonia combines with part of the carbonic acid gas and forms carbonate of ammonia, a very volatile salt which rapidly changes to a vapor and is lost in the atmosphere. This causes a great loss of nitrogen during the rapid decomposition of the manure. This loss can be detected by the well known odor of the ammonia which is particularly noticeable about horse stables and piles of horse manure. Besides these gases a number of compounds of nitrogen, potash, etc., are formed which are soluble in water. It is these that form the dark brown liquid that sometimes oozes out from the base of the manure heap. At the Cornell University Agricultural Experiment Station, the following experiment was carried out to find out how much loss would take place from a pile of manure: "Four thousand pounds of manure from the horse stable were placed out of doors in a compact pile and left exposed from April 25th to September 22d. The results were as follows:" ----------------------------+-------------+--------------+---------- | April 25. | Sept. 22. | Loss | | | per cent. ----------------------------+-------------+--------------+---------- Gross weight | 4,000 lbs. | 1,730 lbs. | 57 Nitrogen | 19.6 " | 7.79 " | 60 Phos. acid | 14.8 " | 7.79 " | 47 Potash | 36 " | 8.65 " | 76 Value of plant food per ton | $2.30 | $1.06 | ----------------------------+-------------+--------------+---------- This shows a loss of more than half the bulk of the manure and more than half the plant food contained in it. CHECKING THE LOSSES