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Efficacy and Economics of Herbicidal Weed Management in Monsoon Rice of Bangladesh

A. K. M. Mominul Islam
Weed Management Laboratory, Department of Agronomy, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Fahima Sultana Popy
Weed Management Laboratory, Department of Agronomy, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Ahmed Khairul Hasan
Department of Agronomy, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Md.Parvez Anwar
Weed Management Laboratory, Department of Agronomy, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Weed management is a challenging task in sustainable rice production. Physical and cultural methods of weed control are laborious and expensive, whereas chemical control is cheaper and less time consuming despite of some detrimental effect on environment with its inappropriate application. Considering these points, an investigation was conducted during July–December 2015 to find out appropriate weed management practices for inbred and hybrid rice. The experiment comprised of four rice varieties (two inbred; BRRI dhan49 and Binadhan-7, and two hybrids; Dhani gold and Agrodhan-12); and eight herbicidal weed control treatments (season-long weedy or weed free, Pretilachlor fb Penoxsolum or 2,4-D dimethyl amine, Pendimethalin fb Penoxsolum or 2,4-D dimethyl amine, Pretilachlor or Pendimethalin fb one-time hand weeding). Eleven weed species belonging to five families were observed in the experimental plots. The highest weed density and dry weight were found in season-long weedy treatment and the lowest one was found in Pretilachlor fb one-time hand weeding. The highest above ground crop biomass (9.7 t ha^-1) and harvest index (46.3%) were obtained from the hybrid variety Agrodhan-12 and the lowest biomass (8.3 t ha^-1) was obtained from the inbred variety Binadhan-7. Season long weed free condition resulted the highest above ground crop biomass (10.9 t ha^-1), harvest index(48.7%), highest yield increase over control (213.8), weed control efficiency (100%) and gross return (BDT 141480 ha^-1) and the lowest values for all those parameters were obtained from season-long weedy treatment. Season-long weed free treatment combined with Pretilachlor or Pendimethalin fb one-time hand weeding showed the best performance in reducing weed density and increasing above ground crop biomass, but gross return was higher because of high labor wages in these treatments. The highest BCR (2.5) was observed in Pretilachlor fb Penoxsolum. Therefore, from economic view point Pretilachlor fb Penoxsolum is the best combination. But from sustainability view point Pretilachlor or Pendimethalin along with one-time hand weeding may be recommended for effective weed management in inbred and hybrid rice during monsoon season.

Keywords: Weed control; Late summer rice; Herbicides, BCR

Location:

Start Date:

End Date:

Program Area: Pest Management

Commodity: Weed management

Objectives:

Present study was undertaken to assess the weed control efficacy and economics of different herbicidal weed control treatments in different monsoon rice varieties.

Methodology:

Experimental site and soil The experimental site is located at 24°75' N latitude and 90°50' E longitude at an elevation of 18 m above the mean sea level. The experimental area was characterized by non-calcareous dark grey floodplain soil belonging to the Sonatola Soil Series under the Old Brahmaputra Floodplain, Agro-Ecological Zone 9 of Bangladesh (FAO and UNDP, 1988; Islam et al., 2011). The soil of the experimental field was more or less neutral in reaction with pH value 6.8, low in organic matter content (1.96%) and bulk density (1.35 g cm^-3). The land type was medium high with silty-loam in texture (20% sand, 67% silt and 13% clay). Soil contained 0.11% total N, 50.40 ppm available P, 7.36 ppm available S, 0.16 me % exchangeable K. The climate of the locality is tropical in nature and is characterized by high temperature and heavy rainfall during kharif season (April-September) and scanty of rainfall associated with moderately low temperature during rabi season (October-March). During the growing season (July–December, 2015), monthly average maximum temperature, minimum temperature, relative humidity, air pressure, wind speed, solar radiation, dew point, pan evaporation and water temperature were 25.2–32.5 °C, 13.3–26.6 °C, 82.2–87.7%, 998.5–1013.8 mb, 2.33–8.72 km h-1, 269–273 W m^-2,14.9–26.3°C, 1.6–3.9 mm and 17.5–28.6°C, respectively, while monthly total rainfall and sunshine hours were 0–387.9 mm and 84.4–205.9 h, respectively. The soil temperature at a depth of 5, 10, 20 and 30 cm were 27.5–31.3, 21.4–31.7, 21.9–31.3 and 21.0–29.5°C, respectively. Experimental treatments and design The experiment included two factors. Factor A comprising four rice varieties of which two were inbred types (BRRI dhan49 and Binadhan-7) and two were hybrids (Dhani gold and Agrodhan-12). Factor B comprising six different combinations of herbicides, season-long weed-free check and season-long weedy check. The application rates of different herbicides were followed as per manufacturers’ recommendations. All herbicides were applied using 500 L water per hectare with a 2L hand sprayer. Season long weed free plots were maintained through manual weeding. No weeds were allowed to grow in these plots. In weedy checks, no hand weeding or herbicides were used and weeds were allowed to grow till harvest without any disturbance. The experiment was conducted in a randomized complete block design with three replicates. Plant materials The varieties used in the experiment were two inbred namely BRRI dhan49 and Binadhan-7 and two hybrids; Dhani gold and Agrodhan-12. BRRI dhan49 was developed by the Bangladesh Rice Research Institute (BRRI) in 2008. It attains a plant height of 100 cm and gives a grain yield of 5.0–5.5 t ha-1. Binadhan-7 is a short duration high yielding variety with good quality of rice released in 2007 by Bangladesh Institute of Nuclear Agriculture (BINA). The yield ranges between 5.5 to 6.0 t ha^-1. Plant height ranges from 95-115 cm. Dhani gold is a hybrid rice variety marketed by Bayer Crop Science Ltd. Agrodhan-12 is a hybrid rice variety marketed by Petrochem Agro Industries Ltd. The plant height is 100-110 cm. The yield ranges between 6.0 to 6.5 t ha^-1. Crop husbandry The experiment was set up in puddled conditions on 28 July 2015 where rice varieties were fertilized with the recommended dose of fertilizers. Urea was top dressed in three equal splits at15, 30 and 45 days after transplanting (DAT). In addition, hybrid varieties were top dressed with 10 kg ha^-¹ zinc sulphate at 15 DAT. Seedlings were uprooted carefully from the bed and transplanted in the plots according to the layout at the rate of 3 seedlings hill^-1 maintaining 25 cm × 15 cm spacing. Rice was grown as a rainfed crop since rainfall was sufficient. Intercultural operations e.g.gap filling, and drainage were done as per requirement. As there were no remarkable infestation of disease and insect, hence no plant protection measure was taken. ^{Data collection and statistical analysis} Weed species grown in the experimental field were identified and weed density and dry weight were measured at harvest. Dominant weed species were identified using the summed dominance ratio (SDR) which was calculated as per Janiya and Moody (1989).

Source of Information: Journal of Scientific Agriculture 2017,1: 275-293doi: 10.25081/jsa.2017.v1.834 http://updatepublishing.com/journals/index.php/jsa

Article Link (Online Journal):

Funding Source:

1.

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Total Budget (Tk.) :

Achievement/Findings:

Weed management is a difficult task in rice production. Researchers around the world are searching to find out a weed management option that is less laborious, less time consuming, cost-effective and not harmful for the environment. However, before making the final choice of weed control method, farmers’ available resources such as labour, have to be considered first. Present findings show that the application of one pre-emergence herbicide at early growth stages followed by one hand weeding can yielded higher total crop biomass at harvest. Through this practice at least one post emergence herbicide can be replaced by hand weeding without sacrificing yield. Present findings also showed that the cultivars that have rapid canopy coverage ability (hybrid) can suppress the weed more efficiently than slow canopy coverage inbred varieties. Thus based on the findings of the present study it can be recommended that in order to obtain optimum yield, rice growers can use either pre fb post herbicide or pre emergence herbicide one hand weeding to effectively control weeds in their monsoon rice. In addition, weed control efficiency can be improved by growing weed competitive rice genotypes especially hybrid verities.

Knowledge Management: Journal