Talks on Manures Part 52

Phos(phoric) Acid.

-----------+----------------------------+---------------------------- Solids Urine One ton +---------+---------+--------+---------+--------+--------- (2000 lbs). Phos. Phos. Nitrogen. acid. Potash. Nitrogen. acid. Potash.

-----------+---------+---------+--------+---------+--------+--------- Human 20.0 lbs. 21.8 lbs. 5.0 lbs. 12.0 lbs. 3.7 lbs. 4.0 lbs.

-----------+---------+---------+--------+---------+--------+--------- Mean of horse, cow, sheep, and swine 9.4 " 6.2 " 4.3 " 22.5 " 0.4 " 25.4 "

One ton of fresh faeces contains more than twice as much nitrogen, and more than three times as much phosphoric acid, as a ton of fresh mixed animal-dung. The nitrogen, too, is probably in a more available condition than that in common barnyard-dung; and we should not be far wrong in estimating 1 ton of faeces equal to 2 tons of ordinary dung, or about equal in value to carefully preserved manure from liberally-fed sheep, swine, and fattening cattle.

"It is an unpleasant job," said the Deacon, "but it pays well to empty the vaults at least twice a year."

"If farmers," said the Doctor, "would only throw into the vaults from time to time some dry earth or coal ashes, the contents of the vaults could be removed without any disagreeable smell."

"That is so," said I, "and even where a vault has been shamefully neglected, and is full of offensive matter, it can be cleaned out without difficulty and without smell. I have cleaned out a large vault in an hour. We were drawing manure from the yards with three teams and piling it in the field. We brought back a load of sand and threw half of it into the vault, and put the other half on one side, to be used as required. The sand and faeces were then, with a long-handled shovel, thrown into the wagon, and drawn to the pile of manure in the field, and thrown on to the pile, not more than two or three inches thick. The team brought back a load of sand, and so we continued until the work was done. Sand or dry earth is cheap, and we used all that was necessary to prevent the escape of any unpleasant gases, and to keep the material from adhering to the shovels or the wagon."

"Human urine," said the Doctor, "is richer in phosphoric acid, but much poorer in nitrogen and potash than the urine from horses, cows, sheep, and swine."

"Some years ago," said the Deacon, "Mr. H. E. Hooker, of Rochester, used to draw considerable quant.i.ties of urine from the city to his farm. It would pay better to draw out the urine from farm animals."

"The figures given above," said I, "showing the composition of human excrements, are from Prof. Wolff, and probably are generally correct.

But, of course, the composition of the excrements would vary greatly, according to the food."

It has been ascertained by Lawes and Gilbert that the amount of matter voided by an adult male in the course of a year is--faeces, 95 lbs.; urine, 1,049 lbs.; total liquid and solid excrements in the pure state, 1,144 lbs. These contain:

Dry substance--faeces, 23 lbs.; urine, 34; total, 58 lbs.

Mineral matter--faeces, 2 lbs.; urine, 12; total, 14 lbs.

Carbon--faeces, 10 lbs.; urine, 12; total 22 lbs.

Nitrogen--faeces, 1.2 lbs.; urine, 10.8; total, 12 lbs.

Phosphoric acid--faeces, 0.7 lbs.; urine, 1.93; total, 2.63 lbs.

Potash--faeces, 0.24 lbs.; urine, 2.01; total, 2.25 lbs.

The amount of potash is given by Prof. E. Wolff, not by Lawes and Gilbert.

The mixed solid and liquid excrements, in the condition they leave the body, contain about 95 per cent of water. It would require, therefore, 20 tons of fresh mixed excrements, to make one ton of _dry_ nightsoil, or the entire amount voided by a mixed family of 43 persons in a year.

One hundred lbs. of fresh faeces contain 75 lbs. of water, and 25 lbs. of dry substance.

One hundred lbs. of fresh urine contain 96 lbs. of water, and 3 lbs.

of dry substance.

One hundred lbs. of the dry substance of the faeces contain 5 lbs. of nitrogen, and 5 lbs. of phosphates.

One hundred lbs. of the dry substance of the urine contain 27 lbs. of nitrogen, and 10 lbs. of phosphates.

These figures are from Lawes and Gilbert, and may be taken as representing the composition of excrements from moderately well-fed persons.

According to Wolff, a ton of fresh human urine contains 12 lbs. of nitrogen. According to Lawes and Gilbert, 18 lbs.

The liquid carted from the city by Mr. Hooker was from well-fed adult males, and would doubtless be fully equal to the figures given by Lawes and Gilbert. If we call the nitrogen worth 20 cents a lb., and the phosphoric acid (soluble) worth 12 cents, a ton of such urine would be worth, _on the land_, $1.06.

"A ton of the fresh faeces," said the Deacon, "at the same estimate, would be worth (20 lbs. nitrogen, at 20 cents, $4; 21 lbs. phosphoric acid, at 12 cents, $2.70), $6.70."

"Not by a good deal," said the Doctor. "The nitrogen and phosphoric acid in the urine are both soluble, and would be immediately available. But the nitrogen and phosphoric acid in the faeces would be mostly insoluble.

We cannot estimate the nitrogen in the faeces at over 15 cents a lb., and the phosphoric acid at 5 cents. This would make the value of a ton of fresh faeces, _on the land_, $4.09."

"This makes the ton of faeces worth about the same as a ton of urine. But I would like to know," said the Deacon, "if you really believe we could afford to pay $4 per ton for the stuff delivered on the farm?"

"If we could get the genuine article," said the Doctor, "it would be worth $4 a ton. But, as a rule, it is mixed with water, and dirt, and stones, and bricks, and rubbish of all kinds. Still, it is unquestionably a valuable fertilizer."

"In the dry-earth closets," said I, "such a large quant.i.ty of earth has to be used to absorb the liquid, that the material, even if used several times, is not worth carting any considerable distance. Dr. Gilbert found that 5 tons of absolutely dry earth, before using, contained 16.7 lbs.

of nitrogen.

After being used _once_, 5 tons of the dry earth contained 24.0 lbs.

" " " twice, " " " " " 36.3 "

" " " three times, " " " " " 44.6 "

" " " four times, " " " " " 54.0 "

" " " five times, " " " " " 61.4 "

" " " six times, " " " " " 71.6 "

Dr. Vlcker found that five tons of dry earth gained about 7 lbs. of nitrogen, and 11 lbs. of phosphoric acid, each time it was used in the closets. If we consider each lb. of nitrogen with the phosphoric acid worth 20 cents a lb., 5 tons of the dry earth, after being used once, would be worth $1.46, or less than 30 cents a ton, and after it had been used six times, five tons of the material would be worth $11.98, or about $2.40 per ton.

In this calculation I have not reckoned in the value of the nitrogen the soil contained before using. Soil, on a farm, is cheap.

It is clear from these facts that any earth-closet manure a farmer would be likely to purchase in the city has not a very high value. It is absurd to talk of making "guano" or any concentrated fertilizer out of the material from earth-closets.

"It is rather a reflection on our science and practical skill," said the Doctor, "but it looks at present as though the only plan to adopt in large cities is to use enormous quant.i.ties of water and wash the stuff into the rivers and oceans for the use of aquatic plants and fishes. The nitrogen is not all lost. Some of it comes back to us in rains and dews.

Of course, there are places where the sewage of our cities and villages can be used for irrigating purposes. But when water is used as freely as it ought to be used for health, the sewage is so extremely poor in fertilizing matter, that it must be used in enormous quant.i.ties, to furnish a dressing equal to an application of 20 tons of stable-manure per acre."

"If," continued the Doctor, "the sewage is used merely as _water_ for irrigating purposes, that is another question. The water itself may often be of great benefit. This aspect of the question has not received the attention it merits."

PERUVIAN GUANO.

Guano is the manure of birds that live princ.i.p.ally on fish.

Fish contain a high percentage of nitrogen and phosphoric acid, and consequently when fish are digested and the carbon is burnt out of them, the manure that is left contains a still higher percentage of nitrogen and phosphoric acid than the fish from which it was derived.

Guano is digested fish. If the guano, or the manure from the birds living on fish, has been preserved without loss, it would contain not only a far higher percentage of nitrogen, but the nitrogen would be in a much more available condition, and consequently be more valuable than the fish from which the guano is made.

The difference in the value of guano is largely due to a difference in the climate and locality in which it is deposited by the birds. In a rainless and hot climate, where the bird-droppings would dry rapidly, little or no putrefaction or fermentation would take place, and there would be no loss of nitrogen from the formation and escape of ammonia.

In a damper climate, or where there was more or less rain, the bird-droppings would putrefy, and the ammonia would be liable to evaporate, or to be leached out by the rain.

Thirty years ago I saw a quant.i.ty of Peruvian guano that contained more than 18 per cent of nitrogen. It was remarkably light colored. You know that the white part of hen-droppings consists princ.i.p.ally of uric acid, which contains about 33 per cent of nitrogen.

For many years it was not difficult to find guano containing 13 per cent of nitrogen, and genuine Peruvian guano was the cheapest and best source of available nitrogen. But latterly, not only has the price been advanced, but the quality of the guano has deteriorated. It has contained less nitrogen and more phosphoric acid. See the Chapter on "Value of Fertilizers," Page 324.

SALTS OF AMMONIA AND NITRATE OF SODA.