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Crop Establishment in the Flood-prone Ecosystem

A. R. Gomosta
Bangladesh Rice Research Institute, Joydebpur, Gazipur, Bangladesh

S. M. Imamul Huq
Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

This paper discusses the importance of crop establishment of long-term flood-prone deepwater rice (DWR) and short-term flash-flood-prone rainfed lowland rice. In addition, dry broadcast seeding for establishment in the field and crop establishment through ratooning and transplanting of DWR seedlings after the boro harvest are discussed. Both establishment methods can add to production of the normal boro crop. Ratooning of DWR can be accomplished by transplanting DWR seedlings in the boro crop. Therefore, attempts should be made to develop a DWR ideotype that possesses a modem plant architecture, better elongation ability, vigorous ratoon ability, and strong pho-tosensitivity. This will ensure bumper production in the flood-prone boro area, which was previously dominated by DWR before the introduction of irrigated modern rice. Rainfed lowland rice, transplanted in low-lying areas, is often submerged by flash flood. Rash-flood submergence reduces stand density by damaging the plants. The factors that affect submergence tolerance are the determining agent for crop stand. Among them, variety, plant structure, and flooding criteria are important. Among different mechanisms of adaptation, recovery growth during the postsubmergence period is considered to be reestablishment of the crop after flash-flood damage. Recovery growth during the postsubmergence period is determined by variety, recovery period before submergence, time of submergence, and time of N fertilization during the postsubmergence period. Tillering as an indicator of regrowth during the postsubmergence period progressively increases with the increase in recovery period before submergence. However, a tolerant variety regrows faster than a nontolerant variety. In the receding floodwater in medium highland phase 2, farmers usually transplant local T. aman varieties. In these areas, modern high-yielding photosensitive varieties such as BR22 and BR23 are suggested for establishment in place of local T. aman varieties.

Keywords: Flood-prone, Ecosystem, DWR, Rice

Location: Bangladesh Rice Research Institute, Joydebpur, Gazipur, Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Rice

Objectives:

To crop establishment for achieving more yield in fragile environments such as the flood-prone ecosystem.

Methodology:

Deepwater rice is defined as rice that is usually flooded deeper than 50 cm for 1 month or longer during the growing season. In addition, flooding must be sustained for at least 1 month. The definition encompasses all water depths above 50 cm, but there is commonly a distinction between DWR and floating rice. Floating rice grows in more than 100-cm water depth. The cultivars have a strong elongation capacity of 5 to 8 cm d^-1. However, traditional floating rice varieties can even have an elongation rate of 25 cm d^-1. Under normal conditions, seeds are dry-broadcast. If continuous rain prohibits normal land preparation, the land is puddled and germinated seeds are broadcast. If there is a chance of early flooding, seedlings are transplanted in the puddled soil. A transplanted crop usually yields 50% less than a broadcast crop. The seed is broadcast in April and transplanting cannot be practiced earlier than the first part of June, when flood usually appears. So, before the advent of flood, the broad-cast crop completes the development of basal tillers but the transplanted one can hardly get a stand in the field. Thus, the broadcast crop can resist the aggression of floodwater better than the transplanted crop and this accounts for the comparatively higher yield of the broadcast crop. However, our experience with the performance of broadcast and transplanted fields is different. Establishment of the crop stand by broad- casting or transplanting after the boro harvest depends on the advent of floodwater. At Habiganj, when sprouted seeds of BR224 were broadcast and seedlings of 15, 25, and 35 days were transplanted, the crop was not properly established in broadcasting, but the transplanted crop produced around 1 t of rice yield when the field was inundated at IS days after transplanting (DAT) or IS days after sowing (DAS). Grain yield decreased, however, with the decrease in seedling age. Seedlings originated from sprouted seeds could not thrive in the early flooding.

Source of Information: Rice Research and Development in the Flood-Prone Ecosystem. Proceedings of the international workshop on flood-prone rice systems held in Gazipur, Bangladesh, 9-11 January 2001. International Rice Research Institute. 283 p. P-205-223, ISBN 971-22-0197-X

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

We observed a strong negative association between degree of basal tiller damage and the production of nodal tillers in a pruning experiment in the field.. This confirms the finding of Catling and Islam (1979) on the formation of nodal tillers in stem borer-damaged DWR. De Datta and Banerjee (1979) also observed a higher number of nodal tillers when basal tillers were reduced by submergence in Jaladhi I and Jaladhi II. Thus, nodal tilJering ability of DWR is an adaptive and important trait that can be advantageous after droughts, insect attacks, and flash floods that reduce stand density. The higher production of nodal tillers in the case of a lower density of basal tillers was also observed in other experiments. The Rice Fanning System Division of BRRI established BR22 and BR23 in medium highland phase 2 and a grain yield of 4 t ha^-1 was achieved. If this finding is extrapolated to other medium highland phase 2 environments of the country, the production of high-quality food grain from this part of the flood-prone ecosystem is possible. The strategic plan for the extra rice production of 2.5 million tons has earmarked medium highland phase 2 as a target area where modem high-yielding photosensitive varieties are suggested for establishment in place of local T. aman varieties.

Knowledge Management: Journal