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A Comparative Ecological Survey of Weeds in Three Rice Fields

M. Islam
Department of Botany, Bangladesh Agricultural University, Mymensingh.

M. S. Rabman
Department of Botany, Bangladesh Agricultural University, Mymensingh.

Abstract/ Executive Summary:

Three plots of rice field were studied at regular intervals by list and point quadrats in order to assess the frequency. % Cover and some other related characters of the weeds met with. The plots showed variations in soil moisture and weed flora as was evident from their analytic and synthetic characters. Cyperus rotundus, Aneilema vaginatum and Depatrium junceum were most widely distributed harmful weeds and they had relatively high % cover values among the weeds. Anthoceros fusiformis and Riccia fluitans, though found to occur with high frequency as well as % cover value, were not considered harmful. Approximately, 21 % of the weed species were constantly present. 28 % were mostly present and 51 % were seldom present in the three plots surveyed. The results of this investigation indicated that with further studies on the distribution, characteristics and habitat relationships of cropland weeds the most harmful and difficult-to-control weeds may be distinguished and controlled more easily from ecological point of view.

Keywords: Comparative,Ecological survey,Weeds, Rice field

Location: Rajshahi University Campus

Start Date: 00-09-1975

End Date: 00-01-1976

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To assess the frequency. % cover and some other related characters of the weeds

Methodology:

Three plots of high land rice fields, each of 250 X 2)0 decimeters in size, were selected in the Rajshahi University Campus. Plot 1 was 50 cm higher than the plain grassland, plot 2 was at the same level with the grassland and plot 3, 75 cm lower than the grassland. The weed species were surveyed in each of them at fortnight intervals by list quadrat and point frame methods (Levy and Madden, 1933) for a period of five months from September,l975 to January, 1976. Twenty quadrat samples, each of 30 sq cm, were taken at random in each plot and the weed species encountered in each quadrat were listed. From the dat a thus obtained, percentage occurrence values ( Frequency values) of the weeds were calculated : % occurrence No. of samples in which the sp. occurs X 100 No. of samples taken Each point frame, also called point quadrat (Ashby. 1961) consisted of 5 long bicycle spokes set 2.5 cm apart in a horizontal frame and placed vertically on the ground through suitable holes. Fifty such point quadrat samples (ie. 250 points) were studied at random in each plot and the weed species were recorded together with the number of hits secured by them. From the data thus obtained, the U cover values of the weed species were calculated by the following formula. % cover of asp. Number of bits secured by the sp.X 100 Total number of bits made In addition to the above measures (Table 2) relative frequency values of the species were calculated from their % occurrence values. Relative frequency (R. F.) of a % occurrence of the sp.X 100 sp. Sum of % occurrences of all spp. met with. Considering all the weed species studied, Jaccard's community coefficients ( Jaccard, 1912) between the plots were measured to estimate the degree of floristic similarity among them. Community coefficient= b) X 100, where (a+ -c 'a'is the number of species in one plot, 'b' that in another and 'c' that common to the two plots under comparison. This coefficient expressed the % number of common weed species between the pair of plots involved ( Table 4) on the basis of the total number of species in them. Soil moisture content: Soil samples were collected in stoppered bottles from the plots at monthly intervals during the period of study. The depth of collection was 0--10 cm (top-soil) since the root systems of most of the weeds were found to lie within it. The moisture content was calculated on oven dry weight basis (McLean and Cook, 1957 ) by weighing the samples before and after drying to constant weights in an oven at 105°c.

Source of Information: Bangladesh J. Agril, Sci, 6 (2) : 131-142 ; 1979 ISSN 0379-4296

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The plots showed variations in soil moisture and weed flora as was evident from their analytic and synthetic characters. Cyperus rotundus, Aneilema vaginatum and Depatrium junceum were most widely distributed harmful weeds and they had relatively high % cover values among the weeds. Anthoceros fusiformis and Riccia fluitans, though found to occur with high frequency as well as % cover value, were not considered harmful. Approximately, 21 % of the weed species were constantly present. 28 % were mostly present and 51 % were seldom present in the three plots surveyed. The results of this investigation indicated that with further studies on the distribution, characteristics and habitat relationships of cropland weeds the most harmful and difficult-to-control weeds may be distinguished and controlled more easily from ecological point of view.

Knowledge Management: Journal