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Effect of Different Weeding Regimes on the Yield of T. Aus Rice Cv. Br 1

M. Waliullah
Farm Management Division Bangladesh Agricultural University Mymensingh-2202 Bangladesh

M. Siddiqure Rahman
Farm Management Division Bangladesh Agricultural University Mymensingh-2202 Bangladesh

M.A. Samad
Farm Management Division Bangladesh Agricultural University Mymensingh-2202 Bangladesh

Abstract/ Executive Summary:

: An experiment was conducted during aus season of 1993 to study the weeds that are grown in aus rice field, their intensity and critical period of crop weed competition. The treatments were un weeded for first 10, 20, 30, 40, 50, 60 and 70 DAT, weed free thereafter, un weeded till harvesting, weeded for first 10, 20, 30, 40, 50, 60 and 70 DAT, weedy thereafter, weedy till harvest and farmers weed control, two times at 20-25 and 40-45 DAT. Twelve weed species were identified and the predominated weed species were Fimbristylis miliacea L., Cyperus iria; Cyperus difformis L.; Echinochtoa cotonum L. and Monochoria vagina/is and these five species constituted about 57.05% of the total weed vegetation. Among the existing weed species of upland aus rice, Fimbristylis miliacea L. ranked the highest number of weed population (55.08/m2) and its intensity of weed infestation was 3.58. The total intensity of weed infestation in upland aus rice was 20.17. The un weeded till harvest treatment produced highest weed dry weight (20.74 g/m2 } and then decreases gradually when duration of weeded treatment increases and vice versa. The weeding regimes influenced the yield contributing characters significantly. The highest grain yield was produced (3.8 t/ha) in weed free till harvest while the lowest in un weeded treatment (1.3 t/ha). From treatments of weeded and un weeded situation at different DAT it is clear that the crop land of upland aus rice should be kept weed free during 30 to 60 days after transplanting to obtain adequate grain yield of the crop.

Keywords: Rice, Intensity, Family, Weed

Location: Conducted at the village Bhabakhali under Sadar thana, Mymensingh

Start Date: 00-04-1993

End Date: 00-08-1993

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To find out the intensity of weed infestation, critical period of weed competition and to asses the extent of yield loss due to weed competition.

Methodology:

The experiment was conducted at the village Bhabakhali under Sadar thana, Mymensingh during the period from April to August, 1993, Rice cv. BR 1 was used for the study. The treatments were un weeded for first 10, 20, 30, 40, 50, 60 and 70 days after transplanting (DAT) and weed free thereafter, un weeded till harvesting, weeded for first 10, 20, 30, 40, 50, 60 and 70 DAT and weedy thereafter, weedy till harvest and farmers weed control, two times at 20-25 & 40-4b DAT. The experiment was laid out in a Randomized complete block design (RCBD) and replicated thrice and each replication was divided into 17 unit plots where the treatments were placed randomly. The size of each unit plot was 10 square metre having a spacing of 50 em in between plots. Fertilizers were applied at the rate of 62, 45 and 24 kg/ha of N, P₂05 and K₂0 supplied through Urea, TSP and MP, respectively. Intercultural operations were done where necessary according to the treatments. The plots were kept weed free till harvest treatment. Weeds were allowed to grow with the crop plants and no weeding operation was done in un weeded till harvest treatment. Treatments of weed free for first 10, 20, 30, 40, 50, 60 and 70 DAT were maintained by removing weeds for first 10, 20, 30, 40, 50, 60 and 70 DAT and weed free thereafter. The weeds were removed from the plots by hand. The weed species that are found in the experimental plots were identified according to their family. The intensity of weed infestation, percentage of infestation of individual weeds were determined following the formulae and scales . Oven dry weight for each sample of weed was taken and expressed in g/m2 . Data were recorded on crop characters. The collected data were analyzed statistically and the mean differences were adjudged as per Duncan's New Multiple Range Test.

Source of Information: Bangladesh J. Agril. Sci. 30(1): 23-28, January, 2003

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From weed free treatments, it is also depicted that with the increase in weed free period the percentage of yield loss is reduced progressively. When weed free period is extended to 30 OAT the percentage of yield loss was sharply reduced from 58.68% to 42.11%. Weed free upto 50 OAT again reduced the percentage of yield loss from 41.05% to 19. 21%. Similar trend of decrease in percentage of yield loss continued upto 60 OAT weedf ree period. Therefore, it is clear that the period of maximum effect of weed on grain yield of aus rice ranged from 30-60 DAT. In other works, the critical period of weed competition stated somewhere after 20 DAT and it lasted upto 60 OAT. Ahmad (1976) also recommended to keep the land of aus rice weed free from fourth to the sixth week of growth to ensure maximum grain yield. The treatment of farmer's weeding produced similar results of weed free for first 50 OAT or weedy for first 10 OAT. Therefore, if only two weedings to be done they should be performed at somewhere very close to 20 OAT and at somewhere close to 40 OAT.From the above findings it may be concluded that the intensity of weed infestation of upland rice is 20.17 and it should be kept weed free during 30 to 60 days after transplanting in order to have adequate grain yield of the crop.

Knowledge Management: Journal