THE SOLVENT ACTION OF WATER
UPON SOILS.
The almost universal solvent power of pure water has already been alluded to in chapter 2 ([see p. 18]), and illustrated by the analyses of drain and river waters. While these convey a general idea of the chief substances dissolved and carried off, the direct investigation of the solutions actually obtainable from the soil by longer treatment and with no more water than is compatible with the welfare of ordinary crops, necessarily gives somewhat different results. For when drains flow during or after heavy rains the water has not time to become saturated. The following data afford a clearer insight into the actual and possible solvent effects of water in the soil, and its possible adequacy to plant nutrition unaided by acid solvents.
Extraction of Soils with Pure Water.—Eichhorn and Wunder treated soils from Bonn, and from Chemnitz (Saxony) respectively for ten days and four weeks with about one-third of their weight of water; the solutions thus obtained contain in 1,000,000 parts:
| Bonn. | Chemnitz. | |
|---|---|---|
| Silica | 48.0 | 25.7 |
| Potash (K₂O) | 115.4 | 7.5 |
| Soda (Na₂O) | 11.0 | 30.4 |
| Lime (CaO) | 128.0 | 83.6 |
| Magnesia (MgO) | 38.4 | 37.4 |
| Peroxid of Iron (Fe₂O₃) | Trace | 11.7 |
| Alumina (Al₂O₃) | ? | ? |
| Phosphoric acid (P₂O₅) | 31.0 | Trace |
| Sulfuric acid (SO₃) | 100.2 | |
| Chlorid of Sodium (NaCl) | 58.6 | 47.6 |
These figures differ widely in most respects from those given for drain and river waters. Potash especially is far more abundantly present in the Bonn-soil solution than in the drain water, and so is phosphoric acid; while lime is not widely different. Eichhorn therefore calculates that with a reasonably adequate supply of water, these ingredients would fully suffice for a full crop of wheat. The Chemnitz soil, on the other hand, does not yield enough plant-food for more than a very small crop upon the same assumptions.
Continuous Solubility of Soil-ingredients.—It seems to be impossible to exhaust a soil’s solubility by repeated or continuous leaching with water. This was demonstrated in 1863 and 1864 by Ulbricht[111] and by Schultze;[112] their general conclusions have quite lately been corroborated by King,[113] as the result of extended and very careful investigations.
Schultze experimented on a rich soil from Mecklenburg, by continuous leaching with distilled water for six days, one liter passing every twenty-four hours, with the following results.
RICH SOIL FROM MECKLENBURG (Schultze.)
1,000,000 PARTS OF EXTRACTS CONTAINED:
| Total matter dissolved. | Organic and volatile. | Inorganic. | Phosphoric acid. | ||
|---|---|---|---|---|---|
| First | extract | 535.0 | 340.0 | 195 | 5.6 |
| Second | “ | 120.0 | 57.0 | 63 | 8.2 |
| Third | “ | 261.0 | 101.0 | 160 | 8.8 |
| Fourth | “ | 203.0 | 83.0 | 120 | 7.5 |
| Fifth | “ | 260.0 | 82.0 | 78 | 6.9 |
| Sixth | “ | 200.0 | 77.0 | 123 | 4.4 |
| Total | 1,579.0 | 740.0 | 839 | 41.4 | |