The Deacon put on his spectacles and studied the above table carefully for some time. “That tells the whole story,” said he, “you put five tons of fresh manure in a heap, it ferments and gets warm, and nearly one ton of water is driven off by the heat.”
“Yes,” said the Doctor, “you see that over half a ton (1,146 lbs.) of dry organic matter has been slowly burnt up in the heap; giving out as much heat as half a ton of coal burnt in a stove. But this is not all. The manure is cooked, and steamed, and softened by the process. The organic matter burnt up is of no value. There is little or no loss of nitrogen. The heap contained 64.3 lbs. of nitrogen when put up, and 63.9 lbs. after fermenting six months. And it is evident that the manure is in a much more active and available condition than if it had been applied to the land in the fresh state. There was 14.9 lbs. of nitrogen in a soluble condition in the fresh manure, and 21.4 lbs. in the fermented manure. And what is equally important, you will notice that there is 154 lbs. of soluble ash in the heap of fresh manure, and 204 lbs. in the heap of fermented manure. In other words, 50 lbs. of the insoluble mineral matter had, by the fermentation of the manure, been rendered soluble, and consequently immediately available as plant-food. This is a very important fact.”
The Doctor is right. There is clearly a great advantage in fermenting manure, provided it is done in such a manner as to prevent loss. We have not only less manure to draw out and spread, but the plant-food which it contains, is more soluble and active.
The table we have given shows that there is little or no loss of valuable constituents, even when manure is fermented in the open air and exposed to ordinary rain and snows during an English winter. But it also shows that when the manure has been fermented for six months, and is then turned and left exposed to the rain of spring and summer, the loss is very considerable.
The five tons (10,000 lbs.,) of fresh manure placed in a heap on the 3d of November, are reduced to 7,138 lbs. by the 30th of April. Of this 4,707 lbs. is water. By the 23d of August, the heap is reduced to 7,025 lbs., of which 5,304 lbs. is water. There is nearly 600 lbs. more water in the heap in August than in April.
Of total nitrogen in the heap, there is 64.3 lbs. in the fresh manure, 63.9 lbs. in April, and only 46.3 lbs. in August. This is a great loss, and there is no compensating gain.
We have seen that, when five tons of manure is fermented for six months, in winter, the nitrogen in the soluble organic matter is increased from 14.9 lbs. to 21.4 lbs. This is a decided advantage. But when the manure is kept for another six months, this soluble nitrogen is decreased from 21.4 lbs. to 13.2 lbs. We lose over 8 lbs. of the most active and available nitrogen.
And the same remarks will apply to the valuable soluble mineral matter. In the five tons of fresh manure there is 154 lbs. of soluble mineral matter. By fermenting the heap six months, we get 204 lbs., but by keeping the manure six months longer, the soluble mineral matter is reduced to 138 lbs. We lose 66 lbs. of valuable soluble mineral matter.
By fermenting manure for six months in winter, we greatly improve its condition; by keeping it six months longer, we lose largely of the very best and most active parts of the manure.