Weed-free Treatment Research Articles

Parthenium weed (Parthenium hysterophorus) competition with grain sorghum under arid conditions

AbstractParthenium weed is an invasive species in a growing number of countries where it infests numerous crop fields, including sorghum. Two field studies were conducted to quantify the effect of parthenium weed on the performance of grain sorghum at different weed densities (0, 5, 10, 15 and 20 plants m−2) and durations of weed-crop competition (season-long weed-free, weed-free after 2, 4, 6 or 8 weeks, and season-long weedy). Our aim was to identify the density threshold and ideal duration to control parthenium weed in sorghum fields. Both field experiments were planned in a randomised complete block design each with three replications in 2016 and were repeated in 2017. Parthenium weed biomass increased significantly with increasing density and competition duration. The increasing parthenium weed density had a linear negative effect on sorghum growth, yield and yield-contributing traits. The highest yield loss, of up to 66%, was recorded at the highest parthenium weed density of 20 plants m−2 when compared to weed-free treatment. In addition, the season-long competition of this weed with sorghum caused 81% reduction in grain yield over weed-free treatment. According to our results, parthenium weed should be managed below a density of 5 plants m−2 and throughout the crop growth duration in grain sorghum fields as it can cause serious yield losses even at low densities and through strong competition at early as well as late growth stages of the crop.

Efficacy of different post-emergence herbicide in chickpea (Cicer arietinum L.)

A field experiment entitled “Efficacy of different post-emergence herbicide in chickpea (Cicer arietinum L.)” was carried out at the farm of AICRP on Weed Management, Department of Agronomy, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, during Rabi season 2016-17.The investigation was carried out to study the relative efficacy of post emergence herbicides on weed control in chickpea, as well as to study the phytotoxic effect on crop, growth and yield of chickpea. The experiment was laid out in Randomized Block Design with eleven treatments replicated thrice. The treatment comprised of different post-emergence herbicides in different doses and were compared with the cultural methods. The soil of experimental was fairly uniform and levelled and low in available nitrogen, and organic carbon, medium in phosphorus, rich in available potassium and slightly alkaline in reaction. Chickpea (JAKI-9218) was sown on 11th Nov 2016 at 30 x 10 cm spacing with fertilizer dose of 25:50:30 NPK kg/ha. The results revealed that, among the varioustreatments under study, weed free treatment (2Hand Weeding) recorded significantly higher values of major parameters whereas, in herbicidal treatments, the maximum growth and yield attributes were recorded with treatment of Oxyflourfen @ 150 g a.i./ha as a post emergence application at 40 DAS which was at par with treatment Imazethapyr 10% @ 50 g a.i./ha. Among the post emergence herbicides, reduction in weed density, weed dry matter, higher weed control efficiency (84.31%) and lowest weed index (5.07%) was found with Oxyflourfen @ 150 g a.i./ha POE 40 DAS and higher weed index in weedy check (45.90%). Oxyflourfen @ 150 g a.i./ha POE 40 DAS was found most economical with maximum value of GMR (88358 Rs ha-1), NMR(58884 Rs ha-1 ) and B: C ratio (3.00). The net return per hectare was more under cultural practice i.e. two hand weeding at 30 and 50 DAS but the difference was not much when compared to effective post emergence herbicide (Oxyflurofen @ 150 g/ha).

Weed control on growth, yield, and physicochemical properties of tarragon

ABSTRACT Competition from weeds limits tarragon (Artemisia dracunculus L.) production. Field experiments were conducted for two consecutive seasons to evaluate methods of control on weed populations and growth, yield, and oil quality of tarragon. Pendimethalin, metribuzin, and oxyfluorfen, alone, or in combination with rye mulch, were examined for weed control and effects on yield and oil quality. The greatest yield, and essential oil content, were from the weed-free treatment. Pre-emergence application of pendimethalin, which is not yet cleared for use in tarragon, at 0.5 and 1.0 kg∙ha−1 ai, in combination with 1 hand-weeding, or rye mulch, provided higher yields than no weeding. Rye mulch alone, or weeding twice manually, was not as effective. The lowest content of the essential oil methyl chavicol was in plants grown with no weeding, the highest was for the weed-free treatment. Integrating reduced herbicide with hand weeding, or mulch, may lower herbicide use to provide adequate weed control and produce acceptable yield and essential oil content. It needs to be clarified whether there is a residue above acceptable limits in tarragon tissue which could pose a health hazard to humans.

Efficacy of pre-and post-emergence herbicides in maize

A field investigation was carried out at Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola during three consecutive Kharif seasons (2016–2018) to study the relative efficacy of herbicides on weed control in maize. Results revealed that, among the herbicidal treatments, atrazine 0.5 kg/ha fb tembotrione 0.120 kg/ha PoE at 20 DAS produced less weed count and weed dry matter than rest of the herbicides. Among the herbicidal treatments, maximum growth and yield attributes were recorded with treatment of atrazine 0.5 kg/ha fb tembotrione 0.120 kg/ha which was at par with atrazine 0.5 kg/ha fb 2,4-D sodium salt 0.5 kg/ha. Yield reduction varied from 12.49% to 54.17% in the herbicide applied plots as compared to weed free treatment. Atrazine 0.5 kg/ha fb tembotrione 0.120 kg/ha PoE 20 DAS (4.33 t/ha) and atrazine 1.0 kg/ha PE (3.89 t/ha) proved as effective as weed free treatment (4.91 t/ha) and recorded significantly higher grain yield with net monitory returns of 47832/ha and B:C ratio of 3.22.

Tillage and weed management effects on productivity of wheat under dry seeded rice-wheat system on lateritic soils of West Bengal

A field study was conducted during 2016-17and 2017-18 to evaluate the impact of four tillage systems, viz. zero tillage (ZT) both in rice and wheat, conventional tillage (CT) both in rice and wheat, ZT in rice - CT in wheat and CT in rice -ZT in wheat with four weed management practices (recommended herbicide, recommended herbicide + one hand weeding, weed free and weedy check) in dry seeded rice-wheat cropping system on a lateritic soil of West Bengal. Among weed management practices, application of sulfosulfuron + metsulfuron at 0.032 kg/ha at 20 DAS followed by one hand weeding at 40 DAS in wheat was found to be the most effective. The yield of wheat under ZT-ZT was found to be the highest (3.78 t/ha), which was at par with CT-ZT. Advantages in ZT-ZT were to the extent of 23.6 and 21.8% over CT-CT in first and second year, respectively. Among weed management practices, recommended herbicide followed by one hand weeding registered higher yield (3.78 t/ha) and was comparable with the weed free treatment. The highest B:C ratio was recorded in zero tillage in wheat (ZT-ZT and CT-ZT) in combination with the sole application of recommended herbicide. The continuous ZT, especially in wheat with recommended herbicide alone was promising for higher productivity and profitability under dry-seeded rice-wheat system on lateritic soils of Eastern India.

Comparison of milk thistle (Silybum marianum) and cardoon (Cynara cardunculus) productivity for energy biomass under weedy and weed-free conditions

• Milk thistle and cardoon achieved satisfactory biomass yields without irrigation. • Both crops expressed high competition and allelopathy against weeds. • Weeds competition slightly reduced productivity of both crops. • Cardoon achieved greater potential energy yield than milk thistle. Milk thistle ( Silybum marianum [L.] Gaertn.) and cardoon ( Cynara cardunculus L.) are energy plants. However, no studies have been conducted to investigate which of these crops could provide sufficient biomass under reduced inputs (regarding irrigation, fertilization and weed management), although this knowledge is essential for the farmers for decision-making. A 3-year field study was conducted in central Greece to compare the productivity of milk thistle (native ecotype) with that of cardoon (var. C12) under weedy and weed-free conditions, without fertilization and irrigation. During the 3 years of cultivation, cardoon and milk thistle produced a total of 24.56 t ha −1 and 20.89 t ha −1 dry biomass, respectively, in weed-free treatments. Weed competition slightly reduced the productivity of both crops. Therefore, the corresponding biomass yields in weedy treatments were 19.70 and 15.49 t ha −1 . The gross calorific value of milk thistle and cardoon biomass ranged from 15.5 to 16.1 MJ kg -1 and 16.5 to 17.3 MJ kg −1 , respectively. The average across-year potential energy yield in weed-free treatments was 111,870 MJ ha -1 for the milk thistle and 135,330 MJ ha -1 for the cardoon. The corresponding potential energy yields in weedy treatments were 80,130 MJ ha -1 and 113,550 MJ ha −1 . Conclusively, milk thistle and cardoon could provide satisfactory dry biomass for energy use in semi-arid Mediterranean fields without irrigation or weed control inputs (assisted by their high allelopathic potential). Additionally, the cardoon outperformed the milk thistle in productivity.

Growth and Yield of Okra (Abelmoschus Esculentus L. Moench) as Affected by Planting Date and Weeding Regime in Northern Ghana

This paper examines the effects of planting date (early planting, mid-season planting and late-season planting) and weeding regimes (two weeding before harvesting, three weeding before harvesting and weed free plots) on yield of Okra (Abelmoschus esculentus L. Moench) in the Tolon district of Northern Ghana. The results show that different weed species, categorized as broad leaves, grasses and sedges, were dominant depending on the planting date and weeding regime. While there was no significant interaction (p>0.05) between planting date and weeding regime on fruit yield, nor significant impact of planting date as a sole treatment on fruit yield, the results showed the existence of significant effect of weeding regime as a sole treatment on yield and yield parameters of okra (p<0.05). Triple weeding resulted in okra yields comparable to the weed-free treatments (mean of 6000 kg/ha to 6300 kg/ha, p>0.05) but significantly higher (p<0.05) and about triple the yield observed in the treatments with double weeding regimes (mean of 1800 kg/ha to 2300 kg/ha). As cost of production, besides the cost of weeding, remains same for all treatments, Triple weeding is recommended for the small-holder farmer. It is associated with less labor cost compared to continuous weeding in the weed free treatments, and the triple gains in yield could offset the additional labor cost incurred in the triple weeding compared to the double weeding regimes.

Effect of Row Spacing and Weed Management Practices on the Performance of Aerobic Rice

Abstract Direct-seeded rice alternative to transplanted rice system is less labor intensive, easier to plant, and consume less water. The advantages of direct-seeded rice have been proved by many research workers, but yet it is not very much adapted by farmers. Weeds reduce cost effectiveness of direct-seeded rice. A study was conducted to evaluate the effect of different row spacing and weed management practices on the performance of aerobic rice at Agronomic Research Area, University of Agriculture, Faisalabad, during summer season of 2013. Fine rice variety ‘Super Basmati’ was used for experiment in a randomized complete block design with factorial arrangements with three replications. Hand drill sowing with row spacing comprised 15 cm, 22.5 cm, and 30 cm was practiced. Weed scouting hoeing (hand pulling is weed free treatment for comparison with the others and hoeing is a type of mechanical weeding) and pre-emergence herbicide, followed by post-emergence herbicide, were the weed management practices. Weeds data and rice yield parameters were measured. Maximum reduction in weed density (86%) and weed dry weight (79%) was recorded for pre-emergence, followed by for post-emergence herbicide in crop sown at 15 cm row spacing.

Effect of planting methods and weed management practices on yield of green gram {Vigna radiata (L.) R. Wilczek}, weed dynamics vis a vis phytotoxicity in green gram

An experiment was carried out to find out suitable method of planting and weed management in green gram grown during the kharif season of 2014 and 2015. The density of E. colona and C. rotundus was significantly reduced in raised bed planting method. Significant reduction in total dry weight of weeds was obtained in raised bed planting method as compared to conventional and zero till planting method. Maximum weed control efficiency was found in raised bed planting method. Significantly more number of seeds pod-1 were observed in raised bed planting method as compared to conventional and zero till planting method. Seed yield and straw yield were found maximum in raised bed planting method during both years of study and were statistically at par in conventional and zero till planting method. Harvest index was not influenced by planting methods. Phytotoxicity on crop due to different herbicides was similar under different planting methods. Among different weed management treatments, HW at 15 and 30 DAS was found most effective in reducing density and dry weight of weeds during crop growing period except at 15 DAS (where weeding was done after taking observation). Maximum weed control efficiency was observed in HW (15 and 30 DAS). Weedy check treatment resulted in minimum while weed free treatment resulted in maximum number of seeds pod-1. Among the treatments having herbicide application, post emergence application of Imazethapyr @ 100 g ha-1 resulted in maximum seed and stover yield.

Performance of different herbicides on wheat grain yield and correlation between growth and yield attributes of wheat and weeds

A field experiment was conducted at Siswal, Hisar, Haryana during 2016–17 and 2017–18 to study the effect of different herbicides applied alone or mixtures on weeds and yield of wheat (Triticum aestivum). Significantly higher grain yield was obtained in weed free treatment, which was statistically similar with pinoxaden + metsulfuron and pendimethalin fb pinoxaden treatments, but significantly higher than all other treatments during both the years. Weed free, pinoxaden + metsufuron and pendimethalin fb pinoxaden treatments produced 70.9, 67.7 and 64.9; 69.4, 67.0 and 64.3% higher grain yield as compared to weedy check treatment, respectively during 2016–17 and 2017–18. Statistically similar grain yield was recorded in pyroxasulfone and pyroxasulfone + pendimethalin treatments, it was 54.1 and 51.1; 55.3 and 52.4% higher to weedy check treatment, respectively during 2016–17 and 2017–18. Application of flumioxazin and flumioxazin + pendimethalin provided effective weed control, but grain yield was lower due to crop phytotoxicity after first irrigation in light texture soils. Significant positive correlation between grain yield, growth and yield attributes, per cent control of weeds and weed control efficiency, but negative correlation was observed between grain yield and weed dry weight, panicle length, seeds/panicle, test weight of wild oat and weed index.

Response of Arabica Coffee Cultivars to Competition from Beggarticks

ABSTRACT: The goal of this study was to analyze the response of Arabica coffee cultivars grown under three levels of Bidens pilosa (beggarticks) interference. At 30 days after transplanting (DAT) of 14 Arabica coffee cultivars into 11 L pots, beggarticks was seeded in the pots and soon after emergence, three levels of weed infestation were established: none, low (two plants per pot), and high (five plants per pot). Treatments were arranged in a 14 × 3 factorial scheme under a completely randomized design, with four replicates. Coffee plant growth was evaluated at both weed emergence and blossoming (90 DAT) when the experiment was completed. Regardless beggarticks infestation levels, significant effects of cultivars occurred on almost all the coffee growth variables. Specifically, the Arabica coffee cultivars Arara, Asa Branca, and Bourbon Amarelo exhibited greater values for root, leaf, shoot, and whole plant dry matter when compared with the other cultivars. The Arabica coffee cultivars presented lower leaf area increments, and also lower leaf, shoot, and whole plant dry matter accumulation when grown under either low or high infestation levels (between which there were no statistical differences, p>0.05) in comparison with that under the weed-free treatment. However, there were no significant interactions between Arabica coffee cultivars and weed infestation levels for those crop growth variables. We conclude that all Arabica coffee cultivars tested were equally susceptible to B. pilosa competition in this phase of crop implantation.

Influence of Tillage Systems and Selective Herbicides on Weed Management and Productivity of Direct-Seeded Rice (Oryza sativa)

ABSTRACT: Weeds cause considerable damage to rice crop. To ascertain the influence of different weed management practices under different tillage systems, a field experiment was conducted during 2014-15. Experimental design was RCB with split-plot arrangement and with a net plot size of 6 x 2 m. Three tillage systems viz; zero tillage with glyphosate application and conventional tillage with and without stale seed bed, and seven weed management treatments viz; weedy check, manual weeding, oxadiargyl as pre-emergence, pyrazosulfuron as pre-emergence, pyrazosulfuron as post-emergence, fenoxaprop-ethyle + sodium fluoride as post-emergence and fenoxaprop-ethyle + sodium fluoride as post-emergence. Results revealed that all treatments including tillage systems and herbicides significantly (p<0.05) affected weed density and weed dry biomass. Minimum weed density (229.22, 159.22 and 127.77 m-2) and weed dry biomass (68.01, 49.29 and 41.08 g m-2) at 30, 45 and 60 DAS (days after sowing) were recorded for pyrazosulfuron (as pre-emergence), respectively, followed by fenoxaprop-ethyle + sodium fluoride (as post-emergence). Maximum 1000-kernel weight and kernel yield (19.15 g and 3.45 ton ha-1) were recorded for weed free treatments and it was 12 and 57% higher than weedy check. Maximum net benefit and benefit to cost ratio (USD$ 817 ha-1 and 1.76, respectively) were recorded for pyrazosulfuron applied at either pre- or post-emergence stage under zero tillage system. Conclusively, pyrazosulfuron (as pre-emergence) and fenoxaprop-ethyle + sodium fluoride (as post-emergence) gave the best weed control under conventional tillage with stale seed bed system, while pyrazosulfuron exhibited maximum benefit-cost ratio under zero tillage system.

Herbicidal weed control in drill sown spring wheat under Bangladesh condition

Weeds are considered as one of the major factors responsible for current low wheat yield in Bangladesh. Although chemical weed control is well established in many wheat growing countries, in Bangladesh, the herbicides are typically not used by farmers to manage weeds in wheat. Hence, to evaluate the efficacy of pre- and post-emergence herbicides in mechanized drilled sown wheat, a two-year field study was conducted in southwest Bangladesh. The study evaluated the performance of four pre-emergence herbicides (oxadiargyl 80g, pendimethalin 850 g, pyrazosulfuron 15 g, and mefenacet + bensulfuran methyl 550 g a.i. ha-1) applied at 2 days after sowing (DAS) and four post-emergence herbicides (2,4-D 1400 g, ethoxysulfuron18 g, penoxsulam22.5 g, and fenoxaprop 56 g a.i. ha-1) applied at 20 DAS, on weed control efficacy. A season long weed-free and a season long weedy plots were also maintained to compare the results. The weed control option using a single pre- or post-emergence herbicide was not adequate to control weed effectively when weed infestation was relatively higher. The best yield provided by pre-emergence (pendimethalin and oxadiargyl) and post-emergence (2,4-D and ethoxysulfuron) herbicide treatments were respectively 13-15% and 12-17% lower than the yield (4.1-4.2 t ha-1) of weed-free treatment. Post-emergence herbicides fenoxaprop was the best in controlling weeds; however, due to phytotoxic effects on wheat plants, the plots applied with fenoxaprop produced very low yield (2.6-2.8 t ha-1). Similarly, even after good weed control by the post-emergence application of penoxsulam, phytotoxicity on wheat resulting in low yield. The study suggested that the best weed control option for wheat is to use a pre-emergence (pendimethalin or oxadiargyl) followed by (fb) a post-emergence (2,4-D or ethoxysulfuron) herbicides depending upon weed species which would benefit the farmers by providing high weed control efficacy at lower cost compared to manual weeding.

Interference of Palmer amaranth (Amaranthus palmeri) Density in Grafted and Nongrafted Watermelon

AbstractWatermelon [Citrullus lanatus(Thunb.) Matsum & Nakai] grafting is commonly used for management of diseases caused by soilborne pathogens; however, little research exists describing the effect of grafting on the weed-competitive ability of watermelon. Field experiments determined the response in yield, fruit number, and fruit quality of grafted and nongrafted watermelon exposed to increasing densities of Palmer amaranth (Amaranthus palmeriS. Watson). Grafting treatments included ‘Exclamation’ triploid (seedless) watermelon grafted on two interspecific hybrid squash rootstocks ‘Carnivor’ and ‘Kazako’, with nongrafted Exclamation as the control. Weed treatments includedA. palmeriat densities of 1, 2, 3, and 4A. palmeriplants per watermelon planting hole (0.76-m row) and a weed-free control. IncreasingA. palmeridensities caused significant reductions (P <0.05) in marketable watermelon yield and marketable fruit number. Watermelon yield reduction was described by a rectangular hyperbola model, and 4A. palmeriplants planting hole−1reduced marketable yield 41%, 38%, and 65% for Exclamation, Carnivor, and Kazako, respectively. Neither grafting treatment norA. palmeridensity had a biologically meaningful effect on soluble solids content or on the incidence of hollow heart in watermelon fruit.Amaranthus palmeriseed and biomass production was similar across weed population densities, but seed number per femaleA. palmeridecreased according to a two-parameter exponential decay equation. Thus, increasing weed population densities resulted in increased intraspecific competition amongA. palmeriplants. While grafting may offer benefits for disease resistance, no benefits regarding weed-competitive ability were observed, and a consistent yield penalty was associated with grafting, even in weed-free treatments.

Growth, yield and quality of maize (Zea mays L.) as influenced by straw mulching and herbicides

The field experiment was carried out at Punjab Agricultural University, Ludhiana and Regional Research Station Gurdaspur (PAU) during kharif 2017 to assess the effect of straw mulching and weed control treatments on growth parameters, yield and quality of maize. Application of paddy straw mulch at 9.0 t/ha produced significantly higher plant height, dry matter accumulation, leaf area index and grain yield in comparison to 6.25 t/hamulch and no mulch treatments; however, 6.25 and 9.0 t/hamulch treatments remained statistically at par with each other with respect to number of leaves per plant. Straw mulch at 6.25 t/ha also resulted in significantly higher plant height, number of leaves per plant, dry matter accumulation, leaf area index and grain yield than no mulch treatment. Among the herbicide treatments, post-emergence application of tembotrione at 0.088 kg/ha recorded significantly higher plant height, number of leaves per plant, dry matter accumulation, leaf area index and grain yield as compared to pre-emergence application of atrazine at 0.8 kg/ha, atrazine at 1.0 kg/ha and unweeded check but remained statistically at par with tembotrione at 0.110 kg/ha and weed free treatments. Protein and oil contents in maize grains were not significantly influenced by different straw mulch and weed control treatments.

Chemical control of parthenium weed (Parthenium hysterophorus L.) in two contrasting cultivars of rice under direct-seeded conditions

Parthenium weed is an emerging problem in direct-seeded rice due to the suitable microclimatic conditions for its establishment in this system. This two-years field study evaluated the potential of pendimethalin (pre-emergence) and bispyribac-sodium plus bensulfuron-methyl (post-emergence) herbicides to control parthenium weed when applied alone or in combination in two rice cultivars, Basmati-2000 (long duration and tall stature) and Shaheen Basmati (short duration and short stature) under direct-seeded conditions. The cultivar Basmati-2000 had a lower parthenium weed density (27 and 14%) and dry biomass (27 and 25%) but had a greater plant height (8 and 13%), produced more kernels per panicle (8 and 12%) and had a greater grain yield (7 and 9%) when compared to Shaheen Basmati in 2016 and 2017, respectively. The application of pendimethalin followed by bispyribac-sodium plus bensulfuron-methyl provided the highest reductions of 90 and 88% in parthenium weed biomass as compared to the weedy treatment in 2016 and 2017, respectively. In this treatment, rice plants were taller (8 and 10%), having greater panicle lengths (17 and 16%), branches per panicle (11 and 21%), kernels per panicle (9 and 6%), 1000-kernel weight (7 and 9%) and grain yield (33 and 37%) as compared to the weedy treatment in 2016 and 2017, respectively. The highest grain yield and net benefits were recorded in the weed-free treatment. In both years, the sole application of pendimethalin or bispyribac-sodium plus bensulfuron-methyl reduced parthenium weed biomass by 66–69% and 80–82%, respectively as compared to the weedy treatment. Overall, the herbicide treatments followed this order in terms of weed control efficiency, grain yield and economic benefits: pendimethalin followed by bispyribac-sodium plus bensulfuron-methyl > bispyribac-sodium plus bensulfuron-methyl > pendimethalin. In conclusion, rice cultivar Basmati-2000 was more suppressive to parthenium weed due to its tall stature. It also produced higher yields and economic returns than the cultivar Shaheen Basmati. The sequential application of pendimethalin and bispyribac-sodium plus bensulfuron-methyl provided an excellent way to control (ca. 90%) parthenium weed and enhanced the productivity and profitability of both rice cultivars under direct-seeded conditions.

Profitability of abrasive weeding in organic grain and vegetable crops

AbstractWeed competition, especially within the crop row, limits the productivity and profitability of organic crop production. Abrasive weeding, a mechanical alternative to hand weeding, uses air-propelled grits to control small weed seedlings growing within the crop row. Recent research has demonstrated the successful use of abrasive weeding to reduce weed competition and increase yields in organic maize (Zea mays), tomato (Solanum lycopersicum) and green and red pepper crops (Capsicum annuum), but the profitability of this weed control tactic has not been assessed. Our objective was to determine the profitability of abrasive weeding using empirical yield data from three previously published studies, a range of crop prices and revenues, and a range of costs for wages, grit applicator ownership, tractor use, abrasive grits, and fuel. Results suggest that abrasive weeding was not profitable in organic maize production, and may reduce net income by US$223–3537 ha−1 compared with inter-row cultivation alone for weed control. The cost of abrasive weeding in maize was largely dependent on the cost of abrasive grits and the cost to own a four-row grit applicator (US$736–2105 yr−1). However, abrasive weeding was less expensive than hand weeding, especially as the scale of production increased. Abrasive weeding was profitable in tomato and pepper crops and increased net mean income by US$12,251–33,265 ha−1. However, abrasive weeding was not 100% effective and hand weeding for weed-free conditions was always the most profitable approach to in-row weed management in vegetable crops. The profit potential of the hand-weeded, weed-free treatments demonstrates the importance of weed control in high-value specialty crops–even those grown in plastic mulch film. Despite the profit potential for hand weeding observed here, labor is increasingly difficult to source, retain and afford, and abrasive weeding offers a mechanical alternative with 66% less labor required. Further research is needed to improve the efficacy of abrasive weeding and to reduce the cost of abrasive grits and application.

Herbicide based weed management in aromatic rice of Bangladesh

Selection of appropriate weed management strategy helps reduce rice yield loss due to weeds. Despite some undesirable side-effects, no viable alternative is currently available to shift the chemical weed management in rice. However, time of herbicide application is very important with respect to its efficacy. Keeping in mind the inevitability of herbicidal weed control, the current study was designed to evaluate the response of selected aromatic fine rice varieties of Bangladesh to different herbicides based weed management practices compare to farmers’ practices. The experiment was conducted in a randomized complete block design with three replications. The experiment consisted of five aromatic rice varieties; Kalijira, BRRI dhan34, BRRI dhan37, BRRI dhan38 and Binadhan-13, and six different weed management practices comprising no weeding, weed free, mechanical + manual weeding, pre–emergence herbicide + manual weeding, post–emergence herbicide + manual weeding and pre– + post–emergence herbicide. Eleven weed species belonging to five families were observed in the experimental plots. Based on the summed dominance ratio (SDR), grassy weed species Echinochloa crusgalli (SDR of 30.7) was the most dominant species, whereas broadleaf weed Nymphaea nouchali (SDR of 0.83) was the least one. Among the weed control treatments, application of pre–+ post emergence herbicides offered the highest reduction in weed density and biomass at all sampling dates which resulted in minimum crop-weed competition facilitating improvement in the yield contributing characters and finally resulted in the highest grain yield (2.5 t ha−1) and harvest index (30.7%) next to the weed free treatment. The variety BRRI dhan38 gave the highest grain yield (3.4 t ha−1) due to the highest performance of the yield contributing characters among the varieties. In interaction, BRRI dhan38 with pre–+ post–emergence herbicide application gave the highest yield (3.4 t ha−1) apart from the weed free treatment. Being efficient in weed density and biomass reduction as well as the highest yield producer, sequential application of pre–and post–emergence herbicides may be recommended for effective weed management practices in BRRI dhan38J. Bangladesh Agril. Univ. 16(1): 31-40, April 2018

Weed and nitrogen management in direct-seeded rice

A field experiment was conducted during Kharif seasons of 2014, 2015 and 2016 with an objective to assess the feasibility of weed and nutrient management in direct-seeded rice. The experiment was laid out in a factorial RBD with eighteen treatment combinations including six weed management treatments, viz. pretilachlor, pendimethalin, pretilachlor followed by (fb) bispyribac-sodium, pendimethalin fb bispyribac-sodium, weed free and weedy check and three nitrogen (N) levels, viz. 80, 100 and 120 kg N/ha with three replications. Significantly lower weed biomass was recorded with weed free which [2 hand weedings (HW) at 20 and 40 days after seeding (DAS)] was at par with pendimethalin 1.0 kg/ha pre-emergence treatment (PE) fb bispyribac-sodium 0.04 kg/ha, post-emergence treatment (PoE). Similarly, the highest weed control efficiency (WCE, 73.0%) and the lowest weed index (WI) were also recorded with weed free treatment, followed by pendimethalin 1.0 kg/ha fb bispyribac sodium 0.04 kg/ha (WCE, 71.2%). Rice growth and yield attributes, viz. plant height, effective tillers, panicles length, grains/panicle were improved significantly under combine application of PE and PoE herbicides either pendimethalin 1.0 kg/ha or pretilachlor 0.75 kg/ha (PE) fb bispyribac 0.04 kg/ha (PoE) and weed free [2 HW at 20 and 40 DAS]. Further, weed free treatment as well as pendimethalin 1.0 kg/ha fb bispyribac 0.04 kg/ha were found equally effective and recorded significantly higher rice grain and straw yield and nutrient use efficiency (NUE) with higher net returns compared to rest of treatments. Application of 120 kg N/ha significantly increased the plant height, effective tillers/plant, panicle length, grain/panicle, grain and straw yield, N content and NUE % over rest of the treatments in all aspects of yield and yield attributes. It was concluded that 2 HW at 20 and 40 DAS or application of pendimethalin 1.0 kg/ha fb bispyribac-Na 0.04 kg/ha for weed control appeared to be a viable strategy along with 120 kg N/ha for achieving higher and profitable yield of direct-seeded rice.

Integration of chemical and manual control methods for sustainable weed management in inbred and hybrid rice

Herbicidal weed control is gaining popularity in the developing countries but its efficacy still remains unclear. Therefore, an experiment was conducted to find out appropriate weed management practices for inbred and hybrid rice. The experiment comprised of inbred and hybrid varieties (two of each), and eight weed control treatments arranged in randomized complete block design with three replicates. Hybrid varieties performed better in terms of yield attributes and yield than inbred varieties. The highest grain yield (5.3 t ha−1) was obtained from the hybrid Agrodhan-12 and the lowest one (4.3 t ha−1) was from inbred Binadhan-7. Weed free treatment resulted in the highest grain yield (6.1 t ha−1) and the lowest one was with weedy treatment (1.96 t ha−1). The highest grain yield was obtained from Agrodhan-12 in weed free condition (6.9 t ha-1), while the lowest value was in inbred BRRI dhan49 under weedy condition (1.73 t ha−1). Weed-free treatment and the treatments of Pretilachlor fb Penoxsolum, Pretilachlor fb hand weeding, and Pendimethalin fb hand weeding showed similar performances in reducing weed density and eventually resulted in similar and the highest grain yield. Based on these results it may conclude that Pretilachlor applied at 2 days after transplanting (DAT) fb Penoxsolum at 21 DAT is the best weed management option. But from sustainability viewpoint, Pretilachlor or Pendimethalin applied at 2 DAT along with one hand weeding at 35 DAT may be recommended for effective weed management in inbred and hybrid rice during monsoon season.J. Bangladesh Agril. Univ. 15(2): 158-166, December 2017