The name of rice has from time immemorial been so closely associated with Indian agriculture that it is difficult to realize how comparatively small an area is planted with this crop. With the exception of the deltas of the great rivers and the long strip of land fringing the western coast, rice may be called an occasional crop throughout the remainder of the peninsula.
In large part these consist of plants which grew near the margins of the old rivers, and which were carried down by floods, and deposited in the alluvial plains, deltas and estuarine areas of the old Gondwana period.
The moist soil encourages luxuriant thickets of willows (Salicineae), surrounded by dense chevaux-de-frise of wormwood and thornbearing Compositae, and interspersed with rich but not extensive prairies, harbouring a great variety of herbaceous plants; while in the deltas of the Black Sea rivers impenetrable beds of reeds (Arundo phragmites) shelter a forest fauna.
Later came the alluvial silting-up. Slowly, but surely, the deltas of the tributary streams advanced into the lake, floods deposited their burdens of detritus in the deeper places, the lake shallowed and shrank and in its turn yielded to the winding river of an alluvial strath, covered with peat, reeds and alders, and still liable to floods.
In the deltas of shoal rivers, with a strong tide or current and no land visible, a 5 lb lead is substituted for the log-ship; the lead rests on the bottom, and the speed is obtained in a manner similar to that previously described.
Pastoral communities are always scattered very thinly over large areas; agricultural populations may be almost equally sparse where advanced methods of agriculture and labour-saving machinery are employed; but where a frugal people are situated on a fertile and inexhaustible soil, such as the deltas and river plains of Egypt, India and China, an enormous population may be supported on a small area.
Orissa embraces the rich deltas of the Mahanadi and the neighbouring rivers, bounded by the Bay of Bengal on the S.E., and walled in on the N.W.
In the deltas of southern India irrigation is only practised during the monsoon season.
In the Madras presidency and in Mysore irrigation has long assumed a great importance, and the engineering works of the three great deltas of the Godavari, Kistna and Cauvery, the outcome of the genius and indefatigable enthusiasm of Sir Arthur Cotton, have always been quoted as showing what a boon irrigation is to a country.
Until about 27 B.C., when it was overthrown by an unknown king of the Andhra dynasty of the Satavahanas, whose power, originating in the deltas of the Godavari and Kistna rivers, by A.D.