A History of Agriculture in India v1.c9: Chapter 3. Climate and Agricultural Regions

A History of Agriculture in India v1.c9

Language: English

Chapter 3. Climate and Agricultural Regions

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AGRICULTURE is largely conditioned by weather, including rainfall. In India, the success of agriculture depends principally on the monsoon rains.

The areas of very heavy rainfall in India are to the windward side of the Western Ghats, the hills of Assam, and the great Himalayan barrier. These are the watersheds from which originate the major river systems of the country. Elsewhere, in the plateau of the Deccan, the Gangetic plains of northern India, and the plains of southern India, the effects of orography are less pronounced or are completely absent, and the rainfall is only moderate. In the north-west, the Punjab, Haryana, Rajasthan and the adjoining tracts to the north and west constitute the driest area of the country.

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The year may be divided into four seasons, viz. winter (December to February), summer or pre-monsoon period (March to May), monsoon (June to September), and the post-monsoon period (October to November).

Monsoon

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India is truly the land of the monsoon. With the exception of Kashmir, and south-eastern Tamil Nadu, a very large percentage of the annual rainfall over the country occurs during the south-west monsoon period (June to September). In the extreme north, a good proportion of the annual rainfall is contributed by winter precipitation, whereas in south-east Tamil Nadu nearly half the annual rainfall occurs during the post- or retreating monsoon period (i.e. after September).

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With the advance of summer, associated with the ‘northing’ of the sun, insolation increases rapidly over the higher latitudes so that by the end of May the region of the highest air temperature and the lowest atmospheric pressure lies over north-western India and the adjoining areas of Pakistan, Afghanistan, Iran and Central Asia. This low-pressure system takes over control, as it were, of the air currents over Asia, so that the south-east trade winds from the south of the equator, after being diverted into the Arabian Sea and the Bay of Bengal, appear suddenly over the west coasts of India and Burma, respectively, as the south-west monsoon. The Arabian Sea branch of the south-west monsoon, while crossing the Western Ghats, gives copious precipitation over that region, and continues to drift eastwards across the Deccan and the central parts of the country, meeting the bay branch of the monsoon along the trough of low pressure which extends from Orissa to north-western India. The bay branch is deflected by the Arakkan Yomas and turned in its course so as to skirt the northern side of the low-pressure trough while moving along the submontane tracts to the south of the great Himalayan barrier.

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The monsoon does not behave as a steady phenomenon. If that were so, the rainfall would always be orographic, i.e. to the windward side of the mountain barriers along the West Coast, the Arakkan mountains, and the Himalayas. Fortunately, the monsoon currents pulsate with a series of eastern depressions, originating in or reviving over the head of the Bay of Bengal, and moving in a westerly to north-westerly direction across the northern and central India. These depressions occur at intervals during the monsoon season, and divert the humid currents into the central and north-western tracts, thus bringing about a more equitable distribution of rainfall all over the country.

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By mid-September the south-westerly monsoon rapidly withdraws and is termed the ‘retreating monsoon’. This withdrawal gradually leads to the north-easterly air current assuming full sway over the subcontinent and the adjoining seas by January. The north-easterly monsoon, as it is called, is associated with rainy weather over the southern parts of Peninsular India, particularly over Tamil Nadu, from November to the end of January.

Eastern Depressions

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Fluctuations in the intensity of the monsoon are to a very large extent associated with a series of depressions which mostly originate from (or, when they are coming from farther east, are strengthened at) the head of the Bay of Bengal, and travel in a north-westerly direction across the country towards north-western India, causing heavy rainfall along their track. The frequency of such depressions is three or four per month during the monsoon period (June to September). In some years, the frequency of these depressions comes down very much, and then the monsoon rainfall tends to become ‘orographical’ (i.e. confined to the hills and mountains). This phenomenon shows the importance of the depressions for securing a proper spatial distribution of the rainfall over the plains of northern and central India. In years of only a few depressions, droughts occur in the interior regions of the country, chiefly in the north-western and central parts.

Western Depressions

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During November to May, a series of western depressions enter India through the North-West Frontier Province and Baluchistan, and move eastwards across northern India towards north-eastern India (Assam-Bengal). These depressions cause cloudy weather and light rains in the plains, and snowfall in the Himalayas, and are followed by cold waves. The frequency of these western depressions is, on an average, two in November, four or five per month during December to April, and about two in May.

Cyclonic Storms

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The more severe cyclonic storms usually form in the Bay of Bengal and the Arabian Sea during the transition periods, i.e. April to June, and October to December. They enter inland and cause considerable precipitation and damage owing to high winds and, occasionally, tidal waves in the coastal tracts.

Monsoon Behaviour

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To begin with, we may consider the total rainfall during the entire south-west monsoon season, i.e. from June to September. If the deviation of the actual precipitation in a year in a subdivision is more than twice the mean, that year may be defined as a year of flood or drought according as the departure is positive or negative. Generally speaking, the number of floods and droughts tend to equalize over long periods. It is the area with very low rainfall, e.g. Rajasthan, which experiences the greatest number of abnormalities. On the other hand, in areas like Konkan, Malabar and Bengal, where the monsoon rainfall is over 1,000 millimetres, abnormalities are fewer.

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The years 1877, 1899 and 1918 stand out prominently as years of general drought. Such country-wide droughts occur once in about 20 years. These were actually the years of great famine and distress. The years of general flood were 1878, 1892 and 1917. There is, however, no regular periodicity in the occurrence of floods and droughts.

Agricultural Regions

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The following agricultural regions are defined on the basis of climate, crops and stock animals:

I. The Temperate Himalayan Region

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The Temperate Himalayan region may be divided into two subdivisions:

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1. *The Eastern Himalayan Region*: This region includes Mishmi Hills in upper Assam, Sikkim, Bhutan and Nepal. Rainfall is heavy in the outer ranges and there are thick forests of *sal*. This is mainly a tea-growing area. Cultivation of rice is done in some places. Forests are the main source of wealth in this subregion.

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2. *The Western Himalayan Region*: This region includes Kumaon, Garhwal, Himachal Pradesh and Jammu and Kashmir. As compared with the eastern Himalayas, the climate is dry. In the northern parts, there is more of winter rainfall, and the climate is almost of the Mediterranean type. Horticulture, particularly the growing of apples, almonds, cherries, apricots, peaches, pears and plums, occupies a prominent place in the agricultural economy of this region. Other cultivated crops are potato, wheat, maize and rice. Goats and sheep are the principal domestic animals. Diminutive black cattle provide milk as well as draught.

II. The Dry Northern Wheat Region

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This region comprises the Punjab, Haryana, western Uttar Pradesh, western Madhya Pradesh and parts of Rajasthan. The annual rainfall is less than 760 millimetres, and in many places less than 200 millimetres. The soil is alluvial, having been deposited by a large number of rivers in geological times. Wheat, barley, gram, maize and cotton are the chief crops. Cattle are mainly of the Hariana breed. Buffaloes are of the Murrah breed. They give a high milk yield. Camels are exclusively found in this region.

III. The Eastern Rice Region

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This region comprises Assam, West Bengal, Bihar, Orissa, eastern Madhya Pradesh, eastern Uttar Pradesh and parts of Andhra Pradesh. The soil is mainly alluvial. The annual rainfall of the region is over 1,500 millimetres. The main crops are rice, jute, sugarcane and tea. Buffalo is the favourite domestic animal. Male buffaloes are used for ploughing in preference to bullocks. The milk yield of buffaloes and cows is low.

IV. The Malabar Coconut Region

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This region comprises Kerala, the Western Coast strip, Karnataka and the adjoining areas. The annual rainfall of the region is over 2,280 millimetres. The soil is lateritic. This region is important from the point of view of plantation crops, e.g. coffee and rubber. However, the predominant crop is coconut. Other important crops are tapioca, black pepper and cardamom. Rice is the main food crop. Cattle are of poor quality.

V. The Southern Millet Region

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This region comprises the Jhansi Division in southern Uttar Pradesh, central Madhya Pradesh, western Andhra Pradesh, western Tamil Nadu, eastern Maharashtra and parts of Karnataka. The rainfall of the region is 500-1,000 millimetres. The soil is partly black cotton and partly lateritic. Sorghum, pearl-millet, cotton and groundnut are the chief crops. The principal animals are sheep. The cattle give a poor milk yield.

References

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Das A.K. and Srivastava, B.N. *Introduction to Meteorology*, Indian Press Ltd, Allahabad, 1933 Eliot, J. *Climatological Atlas of India*, Director-General Meteorological Observatory, Poona, 1906 India, Meteorological Department, *Cloud Atlas*, Manager of Publications, Delhi, 1937 Ram Das, L.A. Rainfall and Agriculture, *Indian J. Meteorology and Geophysics*, I, 262-274, 1950 Ram Das, L.A. *Weather and Indian Farmer*, Manager of Publications, Delhi, 1946