No. 1 is a very fertile alluvial soil from East Friesland, formerly overflowed by the sea, but for 60 years cultivated with corn and pulse crops without manure.
No. 2 is a fertile soil near Göttingen, which produces excellent crops of clover, pulse, rape, potatoes, and turnips, the two last more especially when manured with gypsum.
No. 3 is a very barren soil from Lunenburg.
When washed with water in the manner described in pages 70 to 73, they gave, respectively, from 1000 parts of soil—
| No. 1. | No. 2. | No. 3. | |
| Soluble saline matter, | 18 | 1 | 1 |
| Fine earthy and organic matter (clay), | 937 | 839 | 599 |
| Siliceous sand, | 45 | 160 | 400 |
| 1000 | 1000 | 1000 |
The most striking distinction presented by these numbers is the large quantity of saline matter in No. 1. This soluble matter consisted of common salt, chloride of potassium, sulphate of potash and gypsum, with a trace of sulphate of magnesia, sulphate of iron, and phosphate of soda. The presence of this comparatively large quantity of these different saline substances,—originally derived, no doubt, in great part from the sea,—was probably one reason why it could be so long cropped without manure.
The unfruitful soil is much the lightest of the three, containing 40 per cent. of sand; but this is not enough to account for its barrenness—many light soils containing a larger proportion of sand, and yet being sufficiently fertile.
The finer portions separated from the sand, and soluble matter, consisted in 1000 parts of
| No. 1. | No. 2. | No. 3. | |
| Organic matter, | 97 | 50 | 40 |
| Silica, | 648 | 833 | 778 |
| Alumina, | 57 | 51 | 91 |
| Lime, | 59 | 18 | 4 |
| Magnesia, | 8½ | 8 | 1 |
| Oxide of iron, | 61 | 30 | 81 |
| Oxide of manganese, | 1 | 3 | ½ |
| Potash, | 2 | trace. | trace. |
| Soda, | 4 | ” | ” |
| Ammonia, | trace. | ” | ” |
| Chlorine, | 2 | ” | ” |
| Sulphuric acid, | 2 | ¾ | ” |
| Phosphoric acid, | 4½ | 1¾ | ” |
| Carbonic acid, | 40 | 4½ | ” |
| Loss, | 14 | — | 4½ |
| 1000 | 1000 | 1000 |
1. The composition of No. 1 illustrates the first of those general deductions above stated, that a considerable supply of all the species of inorganic food is necessary to render a soil eminently fertile. Not only does this soil contain a comparatively large quantity of soluble saline matter, but it contains also nearly 10 per cent. of organic matter, and, what in connection with this is of great importance, 6 per cent. of lime. The potash and soda, and the several acids, are also present in sufficient abundance.