A History of Agriculture in India v1.c8.s2.t4: Laterites
A History of Agriculture in India v1.c8.s2.t4
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Laterites
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Laterite is a soil type peculiar to India and some other tropical countries, characterized by the intermittent occurrence of moist climate. In formation it varies from compact to vesicular rock composed essentially of a mixture of hydrated oxides of aluminium and iron, with small quantities of manganese oxides, titania, etc. It is produced by the atmospheric weathering of several types of rocks.
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Laterites may break and be carried to lower levels by streams. When redeposited, they become a compact mass by the segregative action of the hydrates. Thus there are high-level laterites resting on the rocks, and low-level laterites formed in the usual way of detrital deposits.
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Fig. 5. The Indo-Gangetic plain in the Punjab has a rich alluvial soil, which produces bumper crops of wheat and rice
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Fig. 6. The deep black soils in the Pune District, Maharashtra, produce bumper crops of cotton, sugarcane and rice. The fields are dotted with trees of mango and *Acacia nilotica*. In the background are the flat-topped mountains of the Deccan Trap
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Fig. 7. The medium black cotton soil of trap and gneissic origin in the Coimbatore District, Tamil Nadu, yields rich crops of cotton and sugarcane
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Fig. 8. Barren Archaean granite is covered with a thin layer of soil at Hampi, in the Bellary District, Karnataka, Good soil is found only in the low-lying areas
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Laterites are specially well developed on the summits of the hills of Karnataka, Kerala, Madhya Pradesh, the coastal region of Orissa, south Maharashtra, Malabar and part of Assam. All lateritic soils are generally very poor in lime and magnesia, and deficient in nitrogen. Occasionally, the P₂O₅ content may be high, but there is deficiency of K₂O.
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In Tamil Nadu, there are both high-level and low-level laterites which are formed from a variety of rock materials under certain climatic and weather conditions. They are both in-situ and sedimentary formations, and are found along the coastal region where rainfall is heavy and the climate humid. The laterites at lower elevations grow rice, whereas those at higher elevations grow tea, cinchona, rubber and coffee. The soils are rich in nutrients and contain 10 to 20 per cent organic matter.
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In Coorg, the laterite appears sporadically almost all over the district. In Maharashtra it is found only in Ratnagiri. In the soils of Ratnagiri, coarse material is found in large quantities.
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In Kerala, in between the broad sea belt consisting of sandy soil and sandy loams and the eastern regions comprising forest and plantation soils, the mainland contains residual laterite. It is poor in total and available P₂O₅, available K₂O and CaO.
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The laterite soils of Karnataka are comparable with the laterites found in Malabar, the Nilgiris, etc. The soils have very low lime content on account of severe leaching and erosion.
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In West Bengal, the area between the Damodar and the Bhagirathi is interspersed with some basaltic and granitic hills with a laterite capping.
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In Bihar, the laterite occurs principally as a cap on the higher plateau, but is also found in fair thickness in some valleys.
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The laterites of Orissa are largely found capping hills and plateaus, occasionally in considerable thickness. Two types of laterites have been distinguished: (i) the laterite murrum, and (ii) the laterite rock. These are also found occurring together.