Jackson et al. (1982) noted that it was the so-called floating varieties of rice which have the capacity to elongate in response to the rising floodwaters and, thus, can be grown in "very deep water (2-5 m maximum depth)". The term 'deepwater rice' is used here in preference to 'floating rice' and includes all of the many varieties of rice which can be grown where natural flooding of the fields is between 1 and 5 m in depth. A useful general review of rice, which contains comparative information on deepwater rice and definitions of the morphological and other terminology, is that of De Datta (1981).

In Bengali (or Bangla), the main language of Bangladesh and West Bengal, deepwater rice is one of the two monsoon season rice crops known as "Aman". As almost all deepwater rice is sown, with the seed being broadcast directly onto the soil, nowadays it is usually termed "Broadcast Aman", although correctly in Bengali the full name is "jali aman" (jali appearing to mean no more than "flooded").

This distinguishes it from the summer rice grown in unflooded or only shallowly flooded fields, which is transplanted and hence termed "Transplanted Aman".

There are two other rice crops - the spring sown and early summer harvested, "Aus" and the winter "Boro" crop. The aus is a rapidly growing, short-duration crop, traditionally sown in deeper damp areas in January or thereabouts and harvested in late May or early June, commonly from fields beginning to fill with flood waters. Although low-yielding it is a useful crop providing a source of food to carry the people through what otherwise could be a very lean period before the aman harvest. Although capable of given the highest yields of any of the four rice crops, the boro crop historically has been limited in area because of the dependency on irrigation for its growth in the dry winter. The spread of tube wells bringing deep aquifer water to the surface has led to a rapid expansion in the boro cultivation. Although the greater yield has been of short-term benefit, arguably an essential benefit, there are drawbacks to this spread and all may not be as well as the enthusiastic proponents had envisaged. That, however, is another story and not mine to tell.

Where is it grown?

This map shows the areas recognised as used for deepwater rice cultivation in around the mid-1980s. The precise area probably was never very accurately known - the figure was given as "nearly 5 million acres" (in excess of 2 million hectares) by BRRI (1960). In total it was the greatest area under any form of rice in the country. The introduction under international funding of tubewells (shallow for irrigation and deep for drinking water) in the mid-1980's has altered this land use pattern but I have no accurate figures on the extent of the abandonment of deepwater rice in favour of "boro". I have commented on this, however - see below...

In my letter to Ecologist" (click here, I described how an article "Banking on a Flood-Free Future? Flood mismanagement in Bangladesh" (The Ecologist, Sept/Oct 1992) was somewhat misleading. During my time in Bangladesh, I sought information on the source of water which filled the beels (the quite enormous saucer shaped depressions which make up the floodplains). Despite several large-scale studies which were underway at that time, nobody could give me any definite answers. A fair consensus seemes to be that the great rivers contribute in two ways. First, there is the overspill of their water - which embankments might prevent. Second, during the monsoon Bangladesh itself receives around 2,400 mm of rain, with some 3,000 mm in peak years, and this is impounded by the rivers. Embankments simply would replace the rivers in this impounding process and flooding still would occur. Even worse, being permanent. embankments would prevent natural drainage as the river levels fall in the autumn. Apart from the disruption this would cause to the complex of the present crucial subsistence crop, deepwater rice, the consequent waterlogging would prevent the winter cultivation of numerous vital crops (such as mustard, onion, water melon, potatoes). All the crops would suffer if inflow of river water was prevented because of the dramatic loss of the vast quantities of silt which annually replenish soil fertility in much of the floodplains. Studies of silt deposition and agronomic atudies show patterns which support this consensus.

A section on "Adapting to the Floods" did an injustice to the farmers and to their traditional deepwater rice crop. It is not a matter of "adapting" - that was done thousands of years ago and to write of 10,000 varieties of "wild rice" is misleading. The deepwater rice may well be the progenitor of most modern rice varieties but it certainly is not wild. A very high degree of sophistication is shown in the careful selection of cultivars for specific depths of flooding and specific periods of flooding. There is no need whatever for fencing (other than to keep the water hyacinth, a serious floating weed, out of rice fields) nor for planting of natural grasses, canes and trees. In fact, interference in the natural pattern of rice cultivation has come from irrigation during the dry winter season (the end result of other donor activity). Increasingly, the farmers are turning to the ostensibly higher yielding winter, boro, rice but the boro harvest comes too late for the sowing of deepwater rice. Thus, the only possible summer crop is being lost. Furthermore, the enlarging area of boro means disappearance of the normal winter break in rice cultivation and the consequent year-round presence of rice in the floodplains is leading to major increases in pest and disease populations. The empty boro fields leave gaps in beels which otherwise would be completely filled with deepwater rice; in windy conditions these gaps allow waves to build up so as to do severe damage to the deepwater rice.

History of deepwater rice research

Research on deepwater rice in Bangladesh, then East Bengal, started at Dhaka (Dacca) in 1917, and a specific deepwater rice research station (right) was opened at Habiganj, Sylhet District, in 1934 (Bangladesh Rice Research Institute, 1974).

The status of insect pests was not reviewed until the first International Seminar on Deepwater Rice in 1974 (Alam, 1975). At that seminar, a call was made for an immediate systematic survey of pests, to be accompanied by careful crop loss assessment studies. The first specific project to undertake such studies was initiated, in 1977, jointly by the Bangladesh Rice Research Institute (BRRI) and the UK Overseas Development Administration (ODA).

©2000 - Brian Taylor CBiol FIBiol FRES 11, Grazingfield, Wilford, Nottingham, NG11 7FN, U.K. Visiting Academic in the Department of Life Science, University of Nottingham

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