Search

To study the influence of weed interference period and planting spacing on the weed pressure and performance of Boro rice cv. BRRI dhan29 an experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University from December 2015 to May 2016. The experiment comprised six weed interference periods (viz. weed free, weed free up to 20 DAT, weed free up to 40 DAT and weed free up to 60 DAT, weed free up to 80 DAT and weedy condition) and three spacing of planting (viz.25 cm × 15 cm, 25 cm × 10cm, 25 cm × 20 cm) following randomized complete block design with three replications. The highest number of total tillers hill-1 (14.98), effective tillers hill-1 (12.98), filled grains panicle-1 (117.9), grain yield (5.40 t ha-1), straw yield (7.94 t ha-1) and biological yield (40.53 t ha-1) were found weed free up to 80 DAT. Considering cost and time consuming, best tillers hill-1 (15.88), effective tillers hill-1 (13.88), filled grains particle-1 (121.70) and grain yield (6.14 t ha-1) were found in spacing 25 cm × 15 cm with weed free up to 80 DAT. Weed density and dry weight were increased with the increasing weed interference period but rice grain yield increased gradually with the decreasing weed interference period. Weed free up to 80 DAT can be recommended from economic view point following the spacing of 25 cm × 15 cm for better weed suppression and higher yield of BRRI dhan29.

Sunflower (Helianthus annuus) is one of the strongest allelopathic crops through incorporation of its residue in soil to control weed. An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, during the period from June to December 2017 to evaluate the effect of sunflower crop residues on weed management and performance of transplanted aman rice. The experiment consisted of four cultivars i.e; BRRI dhan57, Binadhan-7, Binadhan-15 and Binadhan-16 and four sunflower residues treatment such as 0, 0.5, 1.0, 2.0 t ha-1. The experiment was laid out in a randomized complete block design (RCBD) with three replications. Five weed species belonging to four families infested the experimental plots. Weed population and weed dry weight were significantly affected by cultivar and crop residues treatment. The highest percent weed inhibition was found in sunflower crop residues at 2 t ha-1 treatment which was 47.29, 52.03, 51.28, 71.41 and 70.44 percent for Shama (Echinochloa crusgalli), Amrul(Oxalis corniculata L.), Panikachu(Monochoria vaginalis, Sabuj nakful(Cyperus difformis) and Chesra (Scirpus juncoides), respectively. The maximum weed growth was noticed with the cultivar BRRI dhan57 variety and the minimum was found in the cultivar Binadhan-16. The grain yield as well as the yield contributing characters produced by Binadhan-16 was the highest among the studied varieties. The highest reduction of grain yield was obtained in no crop residue treatment. The highest number of effective tillers hill-1, number of grains panicle-1, 1000-grain weight, grain and straw yields were observed in sunflower residues at 2.0 t ha-1 treatment. Binadhan-16 produced the highest grain and straw yields with sunflower residues 2.0 t ha-1 treatment. Results of this study indicate that sunflower residues showed potentiality to inhibit weed growth and it has a significant effect on the yield of transplanted aman rice. Therefore, sunflower residues might be used as an alternative way for weed management effective as well as obtaining higher yield of T. aman rice. [J Bangladesh Agril Univ 2020; 18(3.000): 557-564]

Crop production is a constant battle with weeds, in which weeds, generally, are victorious. Therefore, rather than channeling our efforts into the development of a “silver bullet” to control weeds, the focus should be on sustainable weed management in both natural- and agro-ecosystems. However, sustainable weed management can be a challenge in the context of global climate change. Over the past few decades, global climate change, mostly indicated by phenomena such as increased atmospheric temperature and elevated CO2 levels, is evident due to human activities and natural events. These phenomena also affect regional/local climate, resulting in significant influences on the agricultural systems of a particular region. Rising CO2 levels may give comparative advantages to C3 plants through increased photosynthesis, biomass production and yield, compared to C4 plants. Plants with C4 photosynthetic pathways, on the other hand, are likely to benefit more from rising global temperatures than C3 plants. Thus, the differential responses of C3 and C4 plants to climate change may alter crop–weed interactions and competition outcomes, most likely at the expense of the crop. Climate change will likely cause shifts in weed community compositions, their population dynamics, life cycle, phenology, and infestation pressure. Some weed species may go extinct, while some others may become more aggressive invaders. Weeds are, generally, colonizers and have some unique biological traits and ecological amplitudes that enable them to successfully dominate crops in a habitat with changed environmental conditions. Moreover, climate shifts, especially erratic rainfall and drought, may affect herbicide selectivity and efficacy or the success of bio-control agents resulting in an establishment of a mixed and complex population of C3 and C4 weed species adding to the complexity of weed management. Although elevated CO2 levels will stimulate the productivity of major C3 crops, most troublesome agricultural weeds will likely be more responsive to a rise in CO2 than crops, and thus may dominate the agro-ecosystem. It is predicted that, as temperature rises, the majority of the C4 weeds will flourish and will pose serious crop yield losses. Understanding and assessment of the impact of simultaneous changes in multiple climate factors and their complex interactions on crops and weeds are therefore necessary to formulate an adaptive weed management approach and build resilience. Moreover, strategic policies and strong actions need to be taken to reduce the root causes of CO2 and other greenhouse gas emissions to minimize the impact of climate change on weed biology and management.

Parthenium hysterophorus is an invasive weed species that competes aggressively with other plants and is also allelopathic. It poses a significant risk to human health, livestock, the environment, soil, and agriculture. However, given some clinical studies, its potential for antidiabetic, antioxidant, antitumor, herbicidal, pesticidal, and antimalarial therapies should be researched further in attempts to discover more relevant applications. It can be used as a nutrient-dense, readily available, and cheap fertilizer. Parthenium can also be used as an herbicide, an insecticide, and a phyto-remedial mediator to extract metals and dyes from agricultural waste. Here we provide basic information on the morphology, reproduction, environmental impacts, and management of this species. Effects of methanol, ethanol, hexane, acetone, and aqueous (water) Parthenium extracts are described. Because P. hysterophorus is said to be one of the world’s seven worst weeds, some control measures, including mechanical, chemical, cultural, and biological control, are discussed. The allelopathy of this weed is difficult to regulate, and there are both positive and negative interactions between Parthenium and other species due to allelochemical action. Several toxic phenolic compounds produced by P. hysterophorus are responsible for weed suppression, and we discuss details of their mode of action and potential applications.

The study was conducted during winter season (February-June) of 2016 at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh. Fourteen rice varieties namely, BRRI dhan28, BRRI dhan29, BRRI dhan47, BRRI dhan50, BRRI dhan55, BRRI dhan58, BRRI dhan59, BRRI dhan67, Binadhan-5, Binadhan-6, Binadhan-8, Binadhan-10, BRRI hybriddhan3 and Agrodhan14 were grown under weedy and weed- free conditions. Plots with no rice were also maintained to study the natural growth of weed in absence of rice. Primed rice seeds were dry seeded following 25 cm ×15 cm spacing with 5 seeds hill-1 on non-puddled soil. Plots were surface irrigated as and when necessary to maintain aerobic condition (at around field capacity) up to heading stage followed by wet condition from heading to grain filling stage. The results revealed that rice varieties varied widely in yield performance and weed suppressive ability. Among varieties, BRRI dhan59 allowed the minimum weed growth (20.8 g m-2) while Binadhan-5 allowed the maximum weed growth (65.8 g m-2). Grain yield ranged from 2.2 t ha-1 (BRRI dhan55) to 4.67 t ha-1 (Binadhan-5) under weed-free condition and from 0.62 t ha-1 (BRRI dhan55) to 2.48 t ha-1 (BRRI dhan59) under weedy condition. Weed infected relative yield loss ranged from 40.1% to 78.2% among varieties. BRRI dhan59 incurred the least yield penalty (40.1%) while Binadhan-5 performed the best in terms of grain yield (4.67 t ha-1) but its weed inflicted relative yield loss was higher (76.4%) than any other variety with low yield potential. BRRI dhan59, on the other hand, appeared as the most weed competitive variety (only 40.1% relative yield loss) with yield of 4.19 t ha-1. Present study confirms that the varieties tested under study varied widely in terms of weed suppressive ability and yield performance. Considering both yield and weed competitiveness, BRRI dhan59 can be recommended for cultivation following modified aerobic system.

Plant spacing and weeding regime are amongst the key factors determining rice growth and yield through maximum utilization of space, plant nutrients, water and sunlight. Therefore, it is essential to identify optimum spacing and proper weeding regime for ensuring the potential yield of a rice cultivar. A field experiment was carried out at the Agronomy Field Laboratory, Bangladesh Agricultural University (BAU), Mymensingh during July- December 2012 to study the influence of spacing and weeding regime on the performance of transplant aman rice cv. Binadhan-7. The experiment comprised four plant spacings viz. 25 cm × 15 cm, 20 cm × 15 cm, 15 cm × 15 cm and 15 cm × 10 cm, and five weeding regimes viz. no weeding, one weeding at 15 days after transplanting (DAT), two weeding at 15 and 30 DAT, three weeding at 15, 30 and 45 DAT and weed free. The experiment was laid out in a randomized complete block design (RCBD) with three replications. The highest weed density and dry weight were recorded with the spacing of 20 cm × 15 cm and 25 cm × 15 cm, respectively. But the lowest values were observed in the closest spacing of 15 cm × 10 cm. Plant spacing exerted significant influence on most of the plant characters except plant height and 1000-grain weight. The highest and statistically significant grain yield was obtained from 20 cm × 15 cm spacing (6.05 t ha-1) and 25 cm × 15 cm spacing (6.04 t ha-1) because of highest number of filled grains panicle-1 (143.65) and highest number of effective tillers hill-1 (10.13). Weeding regime also had significant effect on all the parameters except 1000-grain weight. The highest grain yield (6.29 t ha-1) was obtained from the weed free condition which produced 37.33% higher yield than unweeded condition (4.58 t ha-1). Interaction between plant spacing and weeding regime significantly influenced all the parameters studied except 1000-grain weight. The highest grain yield (6.71 t ha-1) was obtained from the interaction between 20 cm x 15 cm spacing and three weeding regimes at 15, 30, 45 DAT which was similar to the treatment combination of 15 cm × 15 cm spacing and weed free condition. But maintaining season long weed free condition is not practical from economic view point, therefore Binadhan7 should be transplanted at 20 cm × 15 cm spacing following three times weeding at 15, 30 and 45 DAT for higher yield and effective weed control. [Fundam Appl Agric 2017; 2(3.000): 331-339]

Weed-competitive rice cultivars, a viable tool for integrated weed management of rice-field weeds, may greatly reduce the weed pressure and excessive dependence on herbicide in controlling weeds. Based on this premise, field experiments were conducted in 2018 and 2019 during the monsoon and winter rice-growing seasons at the Agronomy Field Laboratory of Bangladesh Agricultural University, Bangladesh, to evaluate the weed competitiveness of the selected rice varieties. A total of 42 monsoon and 28 winter rice varieties from Bangladesh were evaluated under “weedy” and “weed-free” conditions in the puddled transplanted system of cultivation. The field experiments were designed with three replications in a randomized complete block design. The results revealed that weed competition greatly reduces the yield of rice, and relative yield loss was 15–68% and 20–50% in monsoon and winter season rice, respectively. The lowest relative yield losses were recorded in monsoon rice from the variety BU dhan 1 (18%) and from the winter rice BRRI hybrid dhan5 (23.7%), which exhibited high weed tolerance. The weed competitive index (WCI) greatly varied among the varieties in both seasons and the monsoon season, ranging from 0.4 to 2.8, and the highest value was recorded from the hybrid variety Dhani Gold followed by BU dhan 1. In winter season rice, the WCI varied 0.25 to 2.4 and the highest value was recorded from the variety BRRI hybrid dhan3, followed by hybrid variety Heera 6. In monsoon rice, hybrid Dhani Gold was the most productive, but BU dhan 1 was the most weed competitive variety. Among the winter-grown varieties, the hybrid Heera 6 was the most productive, and the most weed competitive. Our research confirmed a high degree of variability in weed competitiveness among the 70 Bangladeshi rice varieties tested.

Aerobic rice or dry direct seeded rice is highly vulnerable to weeds because of lack of “head start” over weeds and standing water layer to suppress weeds. The risks of chemical control and the huge cost involvement in mechanical control demand an eco-friendly and cost-effective integrated weed management. Weed competitive rice cultivar may be considered as a viable tool for integrated weed management. In these circumstances, an experiment was designed to evaluate weed competitiveness of some selected winter rice varieties under aerobic soil conditions. The study was conducted during dry season (February to June) 2016 at the Agronomy Field Laboratory and Weed Management Laboratory, Bangladesh Agricultural University, Mymensingh. Fourteen rice varieties namely, BRRI dhan28, BRRI dhan29, BRRI dhan47, BRRI dhan50, BRRI dhan55, BRRI dhan58, BRRI dhan59, BRRI dhan67, Binadhan-5, Binadhan-6, Binadhan-8, Binadhan-10, BRRI hybrid dhan3 and Agrodhan-14 were grown under weedy and weed-free conditions. Plots with no rice were also maintained to observe the natural growth of weed in absence of rice. The experiment was conducted with split-plot design with three replications. Weeding regime was allocated in main plot and rice variety was allocated in sub-plot. Results showed that rice varieties varied widely in their yield performances and weed competitiveness. Among rice varieties, BRRI dhan59 allowed the minimum weed growth (19.2 g m-2) while Binadhan-5 allowed the maximum weed growth (62.8 g m-2). Grain yield ranged from 1.85 t ha-1 (BRRI dhan55) to 3.92 t ha-1 (Binadhan-5) under weed-free condition and between 0.41 t ha-1 (BRRI dhan55) and 2.06 t ha-1 (BRRI dhan59) under weedy condition. Weed inflicted relative yield loss ranged from 43.4% to 82.1% among the varieties. BRRI dhan59 allowed the least yield penalty (43.4%) while Binadhan-5 had the maximum yield penalty (82.1%) due to weed competition. Although Binadhan-5 is the most productive variety (3.92 t ha-1) for aerobic culture but its weed inflicted relative yield loss is higher (82.1%) than many other varieties with low yield potential. On the other hand, BRRI dhan59 appeared as the most weed competitive variety (only 43.4% relative yield loss) with productivity of 3.84 t ha-1. Therefore, weed competitive variety should be considered as a vital tool while designing integrated weed management system for aerobic rice.

On-farm two experiments were carried out at the Fulbaria upazila under Mymensingh district and Agronomy Field Laboratory, Department of Agronomy, Bangladesh Agricultural University (BAU), Mymensingh during the period from November 2011 to March 2012. The experiment comprised ten fields for each of the locations which composed of three weeding regime treatments, namely, unweeded, farmers’ weeded and weed free. The design was randomized complete block with ten replications. Data on weed density, yield contributing characters and yield of wheat were recorded. Except straw yield in Fulbaria all others yield contributing characters were affected significantly due to weeding regime treatment. The highest grain yield was recorded in weed-free treatment compared to farmers weeded and unweeded treatment in Fulbaria. Whereas, in Agronomy Field Laboratory at BAU, the highest grain yield was observed in weed-free treatment which was statistically identical to farmers’ weeded treatment. Five dominant weed species were identified in Fulbaria naimly Cynodon dactylon L. , Cyperus rotundus L. , Alternanthera sessilis L., Polygonum orientale L. and Chenopodium album L. and in Agronomy Field Laboratory at BAU namely Gnaphalium affine L. , Cyperus rotundus L. , Digitaria sanguinalis L., Cynodon dactylon L. and Panicum repens L. Infestation of Cynodon dactylon L. was more in Fulbaria due to control difficulties and Gnaphalium affine L. was more in BAU due to weed seed bank year after year and poor cultural management. So there is scope to increase yield potential of wheat by improving existing weed control practices. Progress. Agric. 2014. 25: 23-30

Till now, herbicide seems to be a cost effective tool from an agronomic view point to control weeds. But long term efficacy and sustainability issues are the driving forces behind the reconsideration of herbicide dependent weed management strategy in rice. This demands reappearance of physical and cultural management options combined with judicious herbicide application in a more comprehensive and integrated way. Keeping those in mind, some agronomic tools along with different manual weeding and herbicides combinations were evaluated for their weed control efficacy in rice under aerobic soil conditions. Combination of competitive variety, higher seeding rate, and seed priming resulted in more competitive cropping system in favor of rice, which was reflected in lower weed pressure, higher weed control efficiency, and better yield. Most of the herbicides exhibited excellent weed control efficiency. Treatments comprising only herbicides required less cost involvement but produced higher net benefit. On the contrary, treatments comprising both herbicide and manual weeding required high cost involvement and thus produced lower net benefit. Therefore, adoption of competitive rice variety, higher seed rate, and seed priming along with spraying different early-postemergence herbicides in rotation at 10 days after seeding (DAS) followed by a manual weeding at 30 DAS may be recommended from sustainability view point.

Growing rice under aerobic soil conditions is a promising water-wise technology under the context of ever-mounting water scarcity, but it is subject to poor stand establishment and high weed pressure. The present study was, therefore, designed to explore the possibility of adopting seed priming as a sustainable tool for weed management in aerobic rice. The trough experiment was established with aerobic rice line Aeron 1 considering four priming techniques: hydropriming, hardening, Zappa® priming and untreated control; and two weeding regimes: weed-free and weedy. Treatments were arranged in a randomized complete block design with four replications. Seed priming significantly improved germination attributes, weed suppressive ability and yield of rice, whilst unprimed control exhibited inconsistent germination, poor stand establishment and less weed competitiveness resulting in poor yield. Seed priming resulted in reduced mean germination time and increased germination percentage, germination index...

Critical period of weed control is the foundation of integrated weed management and, hence, can be considered the first step to design weed control strategy. To determine critical period of weed control of aerobic rice, field trials were conducted during 2010/2011 at Universiti Putra Malaysia. A quantitative series of treatments comprising two components, (a) increasing duration of weed interference and (b) increasing length of weed-free period, were imposed. Critical period was determined through Logistic and Gompertz equations. Critical period varied between seasons; in main season, it started earlier and lasted longer, as compared to off-season. The onset of the critical period was found relatively stable between seasons, while the end was more variable. Critical period was determined as 7–49 days after seeding in off-season and 7–53 days in main season to achieve 95% of weed-free yield, and 23–40 days in off-season and 21–43 days in main season to achieve 90% of weed-free yield. Since 5% yield loss level is not practical from economic view point, a 10% yield loss may be considered excellent from economic view point. Therefore, aerobic rice should be kept weed-free during 21–43 days for better yield and higher economic return.