THE SOILS OF INDIA.
The soils of India have been investigated to some extent by the geological survey of India; by Voelcker, who went there on a special mission to investigate agricultural conditions; and since, more especially by Leather, Bamber and Mann; and by Moreland. Leather’s account is the most complete on the general subject and can best serve as the basis for a review of the entire peninsula.[156]
According to Dr. Leather, “the four main types of soils to be dealt with, and which certainly occupy by far the larger of the Indian cultivated area,” are: The Indo-Gangetic alluvium, covering the chief cultivable areas of the Indo-Gangetic plain; the black cotton soils or regur, occupying the main body of the plateau of the Central provinces (the Deccan) from the Vindhya range south; the red soils lying on the metamorphic rocks of Madras; and the “laterite” soils which are met with in many parts of India. To these should be added the alluvial soils of the Brahmaputra valley, in Assam. It is hardly to be expected that so large an area as that of India, with its diversified topography, and a climate ranging from about four inches of rainfall in the northern Panjab to the world’s maximum in Assam, and southward to typical tropical conditions, could be even thus briefly characterized. The observers have rarely given for the several soils analyzed, special local and climatic data, which cannot always be obtained from the official publications; so that it is not easy to discuss them from the points of view of aridity and humidity.
The Indo-Gangetic Plain.—The general rain-map of India shows the Panjab and Rajputana to be arid throughout; thence eastward the rainfall increases to 25 and 30 inches on the Ganges; notwithstanding which, alkali (reh) is abundant about Aligarh, Meerut and Agra. Thence toward Calcutta there is a steady increase of rainfall until, at the head of the Bay of Bengal, 70 inches is reached.
If under these conditions the Indo-Gangetic plain admits of any generalizations as regards soil composition, it must be attributed in the main to its predominantly alluvial character. It should therefore be relatively rich in lime, magnesia and potash. So far as the first is concerned, Leather remarks that the only rocky particles larger than sand to be found in all this large belt of land is the nodular limestone called kankar, formed by the deposition of calcium carbonate within the soil, at the depth of a few feet. It occurs very generally in India, and as stated above (chapters 9 and 19), this occurrence of calcareous hardpan, of varying hardness, is almost universal in the arid regions. The analysis given in the table, selected as representative from those given by Leather, show that the general forecast is realized in them, as soils of an arid region.
ANALYSES OF SOILS OF INDIA.
NORTHERN INDIA.
| Indo-Gangetic Alluvium. | ||||
|---|---|---|---|---|
| Sotar Valley. Clay Loam.[157] | Changa Manga. Loamy soils. | Ison, Ganges, Doab. Sandy Loams. | Sibpur, Calcutta Clay soils. | |
| Insoluble matter | 81.57 | 81.54 | 88.08 | 73.58 |
| Soluble silica | ||||
| Potash (K₂O) | .74 | .54 | .64 | 1.82 |
| Soda (Na₂O) | .08 | .25 | .09 | |
| Lime (CaO) | 1.44 | .98 | .47 | 1.01 |
| Magnesia (MgO) | 1.97 | 1.72 | .32 | 1.64 |
| Br. ox. of Manganese (Mn₃O₄) | .11 | 7.19 | ||
| Peroxid of iron (Fe₂O₃) | 4.32 | 5.11 | 3.10 | 7.58 |
| Alumina (Al₂O₃) | 5.85 | 4.36 | 4.38 | 9.89 |
| Phosphoric acid (P₂O₅) | .23 | .14 | .08 | .07 |
| Sulfuric acid (SO₃) | ? | .02 | .05 | .00 |
| Carbonic acid (CO₂) | 1.13 | .45 | .37 | .28 |
| Water and org. matter | 2.67 | 4.78 | 2.42 | 5.93 |
| Total | 100.00 | 100.00 | 100.00 | 100.00 |
| Nitrogen | .02 | .082 | .027 | .051 |
| Brahmaputra Alluvium. | ||||
|---|---|---|---|---|
| Assam.[158] | ||||
| Fezpur bank. Old Alluvium. | Lakhimpur New Alluvium. | Golaghat. Nigriling. New Alluvium. | Sipsagar Teela land. New Alluvium. | |
| Insoluble matter | 85.18 | 84.60 | 85.88 | 91.52 |
| Soluble silica | ||||
| Potash (K₂O) | .35 | .24 | .26 | .14 |
| Soda (Na₂O) | .30 | .12 | .23 | .16 |
| Lime (CaO) | .04 | .11 | .03 | .06 |
| Magnesia (MgO) | .46 | .33 | .36 | .20 |
| Br. ox. of Manganese (Mn₃O₄) | ||||
| Peroxid of iron (Fe₂O₃) | 2.08 | 2.78 | 2.74 | 1.52 |
| Alumina (Al₂O₃) | 5.03 | 5.63 | 5.10 | 3.30 |
| Phosphoric acid (P₂O₅) | .05 | .06 | .06 | .06 |
| Sulfuric acid (SO₃) | .02 | .02 | .02 | .02 |
| Carbonic acid (CO₂) | ||||
| Water and org. matter | 5.59 | 6.11 | 5.32 | .18 |
| Total | ||||
| Nitrogen | .14 | .20 | .18 | .08 |
| Laterite Soils. | |||
|---|---|---|---|
| Bengal. | |||
| Lohardaga. | Chota Nagpur. Singhbhum District. | Hazaribagh District. | |
| Insoluble matter | 29.67 | 59.06 | 80.46 |
| Soluble silica | |||
| Potash (K₂O) | .10 | .27 | .38 |
| Soda (Na₂O) | .04 | .32 | |
| Lime (CaO) | .38 | .28 | 1.72 |
| Magnesia (MgO) | .21 | .33 | .38 |
| Br. ox. of Manganese (Mn₃O₄) | .07 | .48 | .50 |
| Peroxid of iron (Fe₂O₃) | 48.71 | 26.64 | 6.12 |
| Alumina (Al₂O₃) | 8.81 | 7.27 | 7.19 |
| Phosphoric acid (P₂O₅) | .64 | .08 | Trace. |
| Sulfuric acid (SO₃) | Trace. | ||
| Carbonic acid (CO₂) | .06 | .16 | .12 |
| Water and org. matter | 11.31 | 5.43 | 2.81 |
| Total | 100.00 | 100.00 | |
| Nitrogen | .010 | .024 | .03 |