3. The use of Peat.—In many parts of the world, and in none more abundantly, perhaps, than in Gt. Britain, is vegetable matter collected in the form of peat. This ought to supply an inexhaustible store of organic matter for the amelioration of the adjacent soils. We know that by draining off the sour and unwholesome water, and afterwards applying lime and clay, the surface of peat bogs may be gradually converted into rich corn-bearing lands. It must, therefore, be possible to convert peat itself by a similar process into a compost fitted to improve the condition of other soils.
The late Lord Meadowbank, who made many important experiments on this subject, found, that after being partially dried by exposure to the air, peat might be readily fermented, and brought into the state of a rich fertilizing compost by the same means which are adopted in the ordinary fermenting of straw. He mixed with it a portion of animal matter, which soon communicated its own fermenting quality to the surrounding peat, and brought it readily in to a proper heat. He found that one ton of hot fermenting manure, mixed in alternate layers with two of half dry peat, and covered by the same, was sufficient to ferment the whole; and subsequently that the vapours which rise from naturally fermenting farm-yard manure or animal matters, would alone produce the same effect upon peat, placed so as readily to receive and absorb them.
As ammonia is one of the compounds specially given off by putrifying animal substances, it is not unlikely that a watering with ammoniacal liquor would materially prepare the peat for undergoing fermentation. At all events it seems possible to prepare any quantity of valuable peat compost by mixing the peat with a still less quantity of fermented manure than was employed by Lord Meadowbank, provided the liquid manure of the farm-yard be collected in a cistern, and be thrown at intervals by means of a pump over the prepared heaps.
One important use also to which I think peat may be applied is, after it is partly dried, to build it into covered heaps, and half burn or char it till it become readily reducible into a fine powder. In this state it would be of great value as a mixture to preserve the virtues of liquid manures of all kinds, of night-soil, and of ammoniacal liquor.
SECTION III.—RELATIVE VALUE OF DIFFERENT
VEGETABLE MANURES.
There are two principles on which the relative value of different vegetable substances, as manures, may be stated to depend—first, on the relative quantity and kind of inorganic matter they contain; and second, on the relative proportions of nitrogen present in each.
1. Valued according to the quantity of inorganic matter they contain—the worth of the several kinds of straw and hay would be represented by the following numbers:—
| Wheat straw, | 70 | to 360 |
| Oat straw, | 100 | to 180 |
| Hay, | 100 | to 200 |
| Barley straw, | 100 | to 120 |
| Pea straw, | 100 | |
| Bean straw, | 60 | to 80 |
| Rye straw, | 50 | to 70 |
| Dry potato tops, | 100 | |
| Dry turnip tops, | 260 | |
| Rape, cake, | 120 |
that is, a ton weight of each of these substances, when made into manure—provided nothing is washed out by the rains—will return to the soil the above quantities of inorganic matter in pounds. Generally, perhaps, these numbers will give the reader an idea of the relative permanent effect of these different kinds of vegetable matter when laid upon the soil. But, by a reference to the facts stated in [pp. 58 to 64], in regard to the quality of the inorganic matter contained in plants, he will satisfy himself, that the effect of these manures on particular crops is not to be judged of solely by the absolute quantity of earthy and saline matter they contain;—that which the turnip-top, for example, or the bean-stalk, returns to the soil, may not be exactly what will best promote the growth of wheat.
2. On the other hand, if the fertilizing value of vegetable substances is to be calculated by the relative quantities of nitrogen they severally contain, we should place them in the following order:—the number opposite to each substance representing that weight of it in pounds, which would produce the same effect as 100 pounds of farm-yard manure, consisting of the mixed droppings and litter of cattle.