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A Study on Weed Vegetation in Boro Rice (irrigated Rice) as Affected by Land Topography in Old Brahmapurtra Flood Plain Agroecological Zone of Bangladesh

Mahfuza Begum
Professor
Department of Agronomy, BAU, Mymensingh 2202

A. A. Mamun
Professor
Department of Agronomy, BAU, Mymensingh 2202

Nur Ahmed
CSO (C.C.)
Head, Entomology Division, BRRI, Gazipur 1701

Z. Iqbal
Researcher
C/O Professor Mahfuza Begum, Department of Agronomy, BAU, Mymensingh 2202

K. P. Halder
CSO
Head, Farm Management Division, BRRI, Gazipur 1701

Abstract/ Executive Summary:

An experiment was conducted at village Boira under Old'Brahmaputra Floodplain (OBFP) Agro-ecological Zone (AEZ) to see the nature and extent of weed vegetation in boro rice fields as affected by land topography i.e. high, medium high, medium low and low land. Number, speices composition, density and dry weight of the weed species were greatly influenced by land topographic unit. The number of infesting weed sp~icies were 33, 31, 26 and 16 belonging to 13, 14, II and II families, respectively, according to descending land elevation. Gramineae, Cyperaceae and Scrophulariaceae contributed the maximum number of weeds in different land types except low land where Gramineae was completely absent. The most important weed species in terms of relative dry weight were Cyperus iria, Monochoria hastata, Fimbristylis miliacea, and Sagittaria guayanensis, according to descending elevation. The highest similarity of weed vegetation was observed between high land and medium high land. The study revealed that with descending elevation the number of weed species specially annuals and intensity of weed infestation decreased.

Keywords: Weed, Topography, AEZ, Rice, Bangladesh

Location: Boira, Mymensingh

Start Date: 01-01-1992

End Date: 31-05-1993

Program Area: Pest Management

Commodity: Insects

Objectives:

To see the nature and extent of weed vegetation in Boro rice fields as affected by land topography i.e. high, medium high, medium low and low land.

Methodology:

The experimental fields were grouped into four categories i.e. i) high, ii) medium high, iii) medium low and iv) low land in relation to seasonal flooding. Twelve fields under each land type were included in the study. The study was carried out through survey on weed infestation in boro rice fields from .superimposed un-weeded strip of the farmers' field. The size of the superimposed strip in each field was 4 m X 2.5 m i.e. 10m2 which was kept un-weeded. The data on weed infestion were collected by using 0.25 m2 quadrat from three spots in each fields from un-weeded strip at the flowering stage of the rice plants. The number of weeds within the quadrat identified species wise and their density per square metre was counted from average number of three samples and converted to number.lm2multiplied by 4. The important value (I. Y.) or relative dry weight (RDW) of species growing with the crop in each AEZ was determined by the following formula:

I.V.= Dry weight of each speices in a community/Dry weight of all speices in a community X 100

The 'weed community growing in association with the boro rice crop in the four topographic unit was compared on the basis of the coefficient of similarity (%).

Source of Information: Indian Agric., 43 (3&4): 143-150

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The study revealed that with descending elevation the number of weed species specially annuals and intensity of weed infestation decreased in Boro rice.

Knowledge Management: Journal