Reduced Weed Density Research Articles

Long-term impact of zero-till residue management in post-rainy seasons after puddled rice and cropping intensification on weed seedbank, above-ground weed flora and crop productivity

Regulation in weed seed recruitment to soil and its emergence is an ecological approach of weed management for sustainable cropping intensification and land restoration. Intensive tillage operations in rice (Oryza sativa L.) - wheat (Triticum aestivum L.) system is a predominant practice in the South East Asian countries. This practice has emerged as an unsustainable crop management options. Consequently, zero tillage (ZT) in post–rainy seasons after conventional tilled (CT) puddled transplanted rice is being adopted to minimize tillage intensity in system in these regions. However, long–term impact of continuous CT in all seasons versus seasonal ZT (in post–rainy seasons) after puddled transplanted rice with crop residues in cropping system mode on above– and below– ground weed density and diversity is not adequately studied. Hence, we examined four tillage based residue management: (i) conventional tillage in each crop of rotation without residue (CT–CT), (ii) conventional tillage in each crop with incorporated residue (CT–CT + R), (iii) conventional tilled puddled transplanted rice – zero tillage in post–rainy season crops without residue (CT–ZT), (iv) conventional tilled puddled transplanted rice – zero tillage in post–rainy season crops with surface residue mulch (CT–ZT + R) each with three levels of crop rotation: (i) rice – wheat (R–W), (ii) rice – chickpea (Cicer arietinum L.) (R–C), (iii) rice – chickpea – mungbean (Vigna radiata (L.) (R–C–Mb) in split–plot design in Kanpur, India. Zero tillage in post–rainy seasons after conventional tilled rice resulted in 11%, 23%, and 13% lower (P < 0.05) weed seed density than CT–CT at 0–7.5, 7.5–15, and 0–15 cm depth, respectively. However, zero-tilled residue management had 15–19% and 10–14% (P < 0.05) higher above–ground weed density compared with CT–CT. Rice-chickpea-mungbean rotation reduced weed seed density by 6–11%, 4–11%, and 6–8% (P < 0.05) than those of rice-wheat and rice-chickpea across depth. In contrast, rice-chickpea-mungbean had 30–38% higher total above–ground weed density than rest of the crop rotations. Post–rainy seasons zero tillage with and without residues attributed higher weed diversity indices (Shannon and Simpson) compared with conventional tillage in seedbank. Importantly, CT–ZT + R with R–C–Mb (interaction) reduced 24% total viable seed density at 0–15 cm depth than CT–CT with R–W. Further, this system brought about 15% and 62% higher rice seed yield and system productivity over CT–CT with R–W, respectively. Conventional tilled puddled transplanted rice – zero tillage with added residues increased 16% and 33% seed yield of wheat and chickpea compared with CT–CT (P < 0.05), respectively. Thus, it can be concluded that zero tillage in post-rainy seasons after puddled transplanted rice and intensive pulse based cropping (rice-chickpea-mungbean) can minimize viable weed seeds in soil vis–a–vis above–ground weed density over time than conventional tillage and rice-wheat system. The reduced weed density could reduce soil fertility degradation, enhance crop/system productivity, restore soil health and provides opportunity for sustainable cropping intensification in rice ecologies of the Indo-Gangetic plains.

Evaluation of weed management efficacy of post-emergence herbicides in blackgram under semi-arid Alfisols

The efficacy of a post-emergence herbicides in managing weeds in blackgram was evaluated during summer and rainy (Kharif) seasons of 2016 at University of Agricultural Sciences (UAS), GKVK, Bangalore, India. The experiments were laid in RCBD with three replications comprising of nine treatments. Major weed species observed were: Cyperus rotundus, Eleuisine indica, Dactyloctenium aegyptium, Borreria articularis, Echinochloa colona, Commelina benghalensis, Euphorbia geniculata, Phyllanthus niruri. The post-emergence application (PoE) of sodium acifluorfen 16.5% + clodinafop-propargyl 8% EC (206.25 + 100 g/ha) has attained significantly higher seed and haulm yield of blackgram (1305 and 2088 kg/ha, respectively) in summer 2016 and (1519 and 2253 kg/ha, respectively) in Kharif 2016, followed by sodium acifluorfen 16.5% + clodinafop-propargyl 8% EC (165 + 80 and 123.75 + 60 g/ha) (1192 and 1808 kg/ha, respectively) in summer 2016 and (1425 and 2095 kg/ha, respectively) in Kharif 2016. Similarly the weed control efficiency in summer and kharif 2016 was higher with sodium acifluorfen + clodinafop-propargyl (330 + 160 g/ha) PoE (93.20 and 91.0%, respectively) and it was followed by sodium acifluorfen + clodinafop-propargyl (206.25 + 100 g/ha) PoE (89.51 and 90.24%, respectively) when compared to weedy check. The increased yield was mainly due to a significant reduction in weed density and biomass, without any phytotoxicity to succeeding finger millet crop under semi-arid Alfisols.

Productivity improvement of sesame by weed management through plastic mulch and herbicides

A field experiment was conducted during the summer season of 2020 and 2021 at Agricultural Experimental Farm of Calcutta University, Baruipur, South 24 Parganas, West Bengal to find out the effect of plastic mulch and herbicides on weed dynamics, productivity and economics of sesame. Among different weed management treatments, plastic mulch was found very effective in reducing weed density and dry weight at 30 and 60 DAS and registered highest weed control efficiency at 30 DAS in 2020 and 60 DAS in both the years and lowest weed index. Sequential application of pendimethalin + imazethapyr 250g / ha at 2 DAS fb pendimethalin + imazethapyr+ fenoxaprop-p-ethyl 100 g a.i./ ha at 20 DAS recorded significantly lower density and dry weight of weeds than application of pendimethalin 750 g/ ha at 2 DAS, pendimethalin + imazethapyr 250g/ ha at 2 DAS and fenoxaprop-p-ethyl 100 g/ ha at 20 DAS. Weed free resulted in maximum seed yield which did not vary significantly from plastic mulch during both the years. The uninterrupted weed growth caused 49.37% and 46.67% yield loss in sesame during 2020 and 2021, respectively. However, the highest B:C ratio was 2.00, observed in plastic mulch + dibbling (considering only 2021, as the yield was highly damaged by “Amphun storm”) which was closely followed by weed free plot (1.69 and 1.14 in both the years 2020 and 2021 respectively).

The Effect of Using Solarized and Methanized Manure on Weeds Control in Eastern Moroccan Saffron Cultivation

Cultivated for its red stigmas, saffron is arguably the most expensive and precious spice in the world. However, saffron production is limited by a number of factors, including weed infestation which causes damage to this crop both quantitatively and qualitatively. Solarization and anaerobic digestion are techniques used to control weeds and plant diseases. It is for this purpose an experiment was conducted in 2018 with an objective to compare solarized manure and that resulting from anaerobic digestion on the development of weeds associated with saffron crop. During the trial, the parameters measured correspond, on the one hand, to morpho-metric measurements and the determination of saffron stigmas yield and, on the other hand, to the determination of density, dry biomass and weed control capacity. In this study, 16 weed species were recorded. The two treatments applied reduced weed density and biomass by about 55% of the weed species, including problematic species such as Cynodon dactylon, Cyperus rotundus and Convolvulus arvensis. However, there was no effect of manure treatment (T2, T3) on the populations of Chenopodium album, Aster squamatus and Medicago truncatula. The average stigmata yield from the addition of digested manure was 4% higher than the control. Similarly, the number, weight and percentage of daughter corms with a large diameter were higher for plants grown on treated manure. It was concluded that the incorporation of treated manure as a soil amendment slightly increased saffron yield and effectively controlled more than half of the weed species present. Keywords: Solarization, saffron, weeds, management strategies, manure, anaerobic digestion

Cereal rye cover crop terminated at crop planting reduces early‐season weed density and biomass in Wisconsin corn–soybean production

AbstractA fall‐established cereal rye (Secale cereale L.) cover crop has potential to provide weed suppression in fields that will be planted with corn (Zea mays L.) and/or soybean [Glycine max (L.) Merr.], reducing the selection pressure for herbicide resistance as part of an integrated weed management approach. However, biomass from an overwintering cover crop can be limited in areas with prolonged cool‐spring growing conditions, like in the Upper Midwest region of the United States. This study was conducted to determine if a cereal rye cover crop grown in Wisconsin and terminated at the time of crop planting could provide effective levels of early‐season weed suppression in corn–soybean systems practicing no‐till soil management. Cover crop biomass, weed biomass, and weed density were assessed at two Wisconsin locations (eight site‐crop‐years total; four site‐years of each corn and soybean) in 2019 and 2020. Cereal rye biomass production at the time of crop planting ranged from 290–1,480 kg ha–1. Overall, no‐till management with a cover crop reduced weed density by 31% and reduced weed biomass by 61% compared with no‐till without a cover crop. These results indicate that the use of a cereal rye cover crop in the Upper Midwest has potential to reduce the exclusive reliance on spring burndown herbicides in no‐till, but limited spring cover crop biomass in this region may diminish the weed‐suppressive effects from this management practice compared with other parts of the United States where higher amounts of cover crop biomass can be achieved at crop planting time.

Evaluation of conservation tillage practices in the production of organic flue‐cured tobacco

AbstractIntensive tillage in flue‐cured tobacco (Nicotiana tabacum L.) contributes to soil erosion and reduced water‐holding capacity of soils. Conservation tillage minimizes soil disturbance by planting a crop directly into the residue of overwintered cover crop. Reducing tillage has been shown to improve soil health (increased rainwater infiltration, improved water‐holding capacity, reduced erosion) and to reduce production costs (fuel and labor). The objective of this study was to compare the effects of conservation and conventional tillage on weed management in organically grown flue‐cured tobacco. Field studies were conducted in Kinston, NC, in 2019 and 2020 and in Rocky Mount, NC, in 2020, comparing the impacts of conventional tillage and conservation tillage on weed emergence and tobacco production. An overwintered cereal rye (Secale cereal L.) cover crop was conventionally tilled or terminated via roller‐crimper and left in place as a mulch prior to transplant of flue‐cured tobacco. Cover crop biomass, weed emergence and biomass, soil resistance, crop yield and quality, and cured leaf chemistry were evaluated. In all environments, conservation tillage with cover crop residue reduced weed density and biomass when compared with conventional tillage treatments. In 2019, cured leaf yield was higher under conservation tillage practices than under conventional tillage. In 2020, environmental conditions in both locations resulted in crop loss. These results indicate that conservation tillage practices may be an effective weed management strategy while improving yields in an organic production system. However, organic flue‐cured tobacco grown under conservation tillage is vulnerable to extreme rain events due to the exclusion of in‐season cultivation.

PRE AND POST CONTROL OF WEEDY RICE AND SELECTED RICE WEEDS WITH PREMIX OF IMAZAPIC AND IMAZAPYR AT DIFFERENT RATIOS

Field experiments were conducted in the rice fields of the Malaysian Agricultural Research and Development Institute in 2018 and 2019, to determine the efficacy of two commercial premix herbicides consisting of imazapic and imazapyr at 70:30 (formulation 1) and 30:70 (formulation 2) applied singly or in sequence for control of weedy rice and other rice weeds. Formulation 1 was applied as PRE at the 0 to 1-leaf stage of weedy rice while formulation 2 was applied as POST at the 3 to 4-leaf stage of weedy rice. Formulation 1 applied PRE at 150 g ai ha-1 with or without sequential application of formulation 2 applied POST at 75 or 150 g ai ha-1 provided complete inhibition of weedy rice. The same rate of formulation 1 applied PRE highly reduced weed density and dry weight of Monochoria vaginalis (99%) and Fimbristylis quinquangularis (93%) as compared to weedy check plots. Formulation 2 applied POST at 150 g ai ha-1 providing lower weed density and dry weight reduction of weedy rice (59 to 65%), M. vaginalis (80 to 81%), and F. quinquangularis (56 to 64%) as compared to those observed in formulation 1 applied PRE at 150 g ai ha-1. These results suggest that although formulations 1 and 2 share the same active ingredients, excellent control of weedy rice and rice weeds could only be achieved with PRE application of formulation 1 at 150 g ai ha-1.

Weed suppression versus water use: Efficacy of cover crops in water‐limited agroecosystems

AbstractWinter cover crops (CC) may facilitate weed management by inhibiting weed seed germination and seedling emergence and suppressing weed growth within the cash crop. In southern New Mexico, with scarce winter precipitation and limited irrigation water, producing sufficient CC biomass for effective weed suppression while conserving water resources is challenging. This study assessed the water requirement to produce a CC with enough biomass for weed suppression benefits during cash crop growth at two locations in New Mexico. Three winter CC species, barley, Austrian winter pea and mustard, grown singly and in a three‐way mix, under three differential irrigation treatments (one, two or three irrigations after emergence) were evaluated for their weed‐suppressive potential. Maize was planted as a cash crop four weeks after winter CC termination. Number of irrigations had no effect on the CC and weed biomass production. All CCs had lower weed density prior to maize planting compared with fallow. Barley and the three‐way mix reduced weed density by 56–96% and 68–95%, respectively. All CC treatments had lower weed biomass at the end of critical period for weed control in maize compared with fallow. Weed biomass at maize harvest did not differ between treatments. The maize yield was consistently higher in conventionally managed, weed‐free subplots, than in unsprayed weedy subplots, suggesting that CCs did not suppress weeds throughout the maize growing season. Except for barley, CCs did not cause reductions in maize yield compared with fallow. Overall, the study suggested that with adequate winter precipitation, weed‐suppressive winter cover crop stands can be produced with just one irrigation at seeding and one supplemental irrigation, making them a viable option in water‐limited agroecosystems.

Effects of mulching on the weed community and grain yield of upland rice cultivars

This study evaluated the effects of mulching on upland rice cultivars Comecru and Cambará and the weed community under four amounts of babassou (Attalea speciosa Mart. ex Spreng.) straw mulching namely: 0, 15, 20, 25 t ha-1 with a view to control weeds. The experiment was laid out in a randomized complete block design in a 2 x 4 factorial scheme with four replications. The rice plant height, percentage of fertile panicles, number of spikelets per panicle, weight of 100 grains and grain yield were assessed. We also assessed the weed community by computing the following phytosociological parameters: density, frequency and the importance value index (IVI) of each species. Babassou straw mulching reduced weed density and dry mass between rows of upland rice cultivars and increased the rice yield. The weed species with the highest Importance Value Index (IVI) in the treatments with no mulching were Cyperus iria, Fimbristylis dichotoma and Digitaria ciliaris. Rice grain yield was increased with the increase in the amount of straw. Comecru cv. had the highest suppressive effect on weeds with significantly higher grain yield (1,214.85 kg-1) than Cambará cv. (878.72 kg ha-1). We conclude that the higher amounts (20 and 25 t ha-1) of babassou straw mulching suppressed weeds, providing less competition with the rice cultivars, which resulted in an increase in the number of rice panicles, weight of 100 grains, spikelet fertility and grain yield in both rice cultivars

Herbicide Efficacy of Spot Spraying Systems in Fallow and Postharvest in the Pacific Northwest Dryland Wheat Production Region.

Real-time spot spraying technology has the potential to reduce herbicide costs and slow herbicide resistance. However, few studies exist on the efficacy of this technology in the Pacific Northwest (PNW). This research compared the herbicide efficacy (reduction in weed density and cover) of WEED-IT and WeedSeeker spot spraying systems to uniform spraying in fallow and postharvest in 2019 and 2020. Weed community types included naturally occurring weeds, natural + Russian thistle (Salsola tragus L.), or natural + kochia (Bassia scoparia (L.) A. J. Scott). Herbicides included glyphosate or the pre-mix bromoxynil + pyrasulfotole. Additionally, herbicide efficacy was studied with short stubble (~10 cm), tall stubble (~25 cm), and normal stubble (~20 cm) with chaff and straw removed. In fallow, herbicide efficacy was 1.5 times higher for uniform applications than for WEED-IT or WeedSeeker in 2019 and 2020. Herbicide efficacy was also 1.9 times higher for uniform applications in postharvest in 2019 but no differences were found in 2020. The weed community impacted herbicide efficacy but herbicide efficacy did not differ between residue management treatments. Finally, WEED-IT and WeedSeeker used 53% less herbicide volume in comparison to uniform applications. This research demonstrated that spot spraying technology can be efficacious and economical for growers in the PNW.

Weed control for sustaining rice production under dry seeding systems in North-Western India

Identification and adoption of effective weed management practice play a fundamental role for a successful dry-seeded rice (DSR). This field experiment was designed to evaluate the impact of weed control options on weed management, productivity, nutrient uptake, and energetics in DSR. Echinochloa crus-galli (L.) Beauv. was the most dominant species followed by Leptochloa chinensis (L.) Nees. Among the weed control options, sequential applications of pendimethalin (1000 g a.i. ha−1) as pre-emergence and pre-mix combination of penoxsulam (1%) plus cyhalofop-butyl (5%) at 130 g a.i. ha−1 at 25 days after sowing (DAS) led to significant reduction in weed density (82.9%) and biomass (80.1%). This resulted in highest rice grain yield (3.92 t ha−1) and nutrient uptake, resulting in considerably higher energy productivity and lower specific energy. Brown manuring combined with application of metsulfuron methyl (10%) plus chlorimuron ethyl (10%) at 4 g a.i. ha−1 at 40 DAS was also effective in controlling weeds. Based on relative advantages of pendimethalin and penoxsulam plus cyhalofop-butyl in sequence over others, this may be recommended for weed control in DSR.

Evaluation of Bio - Efficacy and Phytotoxicity of Glyphosate 41% SL against Weed Flora in Grape Vineyards

The study was evaluated for the bio- efficacy and phytotoxicity of Glyphosate 41% SL against the complex weed flora in grapevines. The experiment was carried out at ICAR- NRC Grapes, Pune with seven treatments replicated thrice. The treatments were imposed at 3-4 leaf stage of weeds in vineyards. All the weed population were niformly distributed in vineyards. All the treatments significantly reduced weed density over untreated control. The highest weed density was recorded with untreated control while, the negligible weed density was recorded in hand weeding followed by Glyphosate 41 % SL @ 4000 ml/ha at 15th, 30th, 45th Days after application. Least dry weight (g/m2) as recorded with Glyphosate 41 % SL @ 4000 ml/ha followed by Glyphosate 41 % SL @ 3000 ml/ha whereas, the maximum dry weight of weed (g/m2) was recorded with untreated control at 45th Days after application. Highest weed control efficacy (%) was recorded with Glyphosate 41 % SL @ 4000 ml/ha followed by Glyphosate 41 % SL @ 3000 ml/ha whereas, negligible weed control efficacy (%) Was recorded with untreated control. The highest yield (kg/vines) was recorded with hand weeding treatments followed by Glyphosate 41 % SL @ 4000. The highest benefit: cost ratio was recorded in the treatment Glyphosate 41 % SL (4000 ml/ha) (1:1.99), while least in control treatment (1:1.77). Applications of Glyphosate 41 % SL @ 4000 ml/ha in grapevines showed highest weed control efficacy (%) and yield per vine (kg/vine) in this investigation.

Effects of Narrow-Windrow Burning on Weed Dynamics in Soybean in Louisiana

The soil seedbank allows for long-term persistence of weed species in agricultural fields. Some weed species can persist in the soil seedbank for extended periods. Restricting inputs into the weed seedbank has a large impact on future population density and influences management practices of these weeds in soybean production systems. Harvest weed seed control (HWSC) tactics incorporate mechanical and cultural management strategies to target weed seeds present at harvest. A 3-year trial was initiated to determine if continual use of the HWSC method, narrow windrow burning, selects for earlier seed set and shattering in Louisiana soybean. No shifts in weed populations or shattering time were observed. However, there was a significant reduction in weed density and the weed seed present in the soil seedbank when HWSC and robust herbicide programs were used in combination. Therefore, utilizing multiple effective weed management strategies is imperative in reducing the soil seedbank.

Biochar and Fertilization Effects on Weed Incidence in Winter Wheat

Biochar, a carbon-rich material, is highlighted to improve soil fertility, simultaneously mitigating climate change by carbon sequestration. Combined with mineral fertilizer, it can increase weediness, the major source of yield loss in agricultural production. Research with biochar was conducted in Eastern Croatia in 2016, with the aim to investigate the influence of biochar and mineral fertilizer on weed infestation and winter wheat yield. Field experiments were set up as a split-plot where biochar (B) was the main factor and fertilization was the sub factor. The main treatments were: B0 (control without biochar), B1-5 t ha−1, B2-10 t ha−1 and B3-15 t ha−1. Fertilization sublevels were F0) without fertilizer and F1) optimal dose of fertilizer. Weediness was determined by counting and measuring aboveground biomass. The treatments with the greatest effect on weediness were B3 and F1 in the winter wheat tillering stage. In the winter wheat ripening stage, treatment B3 obtained the highest weediness and F1 significantly reduced weed density. Biochar treatment B3 increased winter wheat yield by 77% in relation to the control. The application of biochar combined with fertilization affected the level of weediness depending on agroecological conditions, but with a significant increase in yield.

Allelopathy Weed management and yield improvement in mungbean through allelopathic action of sunflower and bermuda grass (a weed) extract in conjunction with irrigation frequencies

Allelopathy is the effect of one plant species by reducing the germination and growth of the neighbouring plants of another species through releasing chemical compounds. It has been reported by many researchers that weeds are major hazard in reducing crop yield but it can be managed effectively through phytotoxic properties of plants. A field study was conducted at Students Experimental Farm, Agronomy Department, Crop Production Faculty, Sindh Agriculture University Tandojam, Pakistan during spring 2019 and repeated during 2020 to validate the previous results. The research conducted to evaluate the allelopathic potential of sunflower and Bermuda grass extracts under various irrigation levels on weeds density and yield of mungbean cultivar ‘AEM-96’. Split plot design having four replications was managed. The experiment consisted of weed control practices: Weedy check, various levels of sunflower and bermuda grass extracts as sole and in combination with each other, different levels of herbicides as alone and in integration with allelopathic plant extracts as well as hand weeding under three irrigation frequencies (2, 3 and 4 watering applications). The analysis variance of results showed that various levels of sunflower and bermuda grass extracts as sole and in combination with each other, different levels of herbicides as alone and in integration with allelopathic plant extracts as well as hand weeding caused significant suppression of weeds and increased in seed yield as compared to weedy check. The combined treatment Atlantis: 0.1 Ltr ha-1 + Puma Super: 0.156 Ltr ha-1 + Sunflower extract: 15 L ha-1 resulted in less weed density (51.6 m-2) and produced maximum seed yield of 2404.4 kgs ha-1. Bermuda grass extract: 15 Ltr ha-1 integration with low dose of herbicides Atlantis: 0.1 Ltr ha-1+ Puma Super: 0.156 Ltr ha-1 showed weed density of 61.3 m-2 resulted seed yield of 2282.1 kgs ha-1. The application of herbicides treatment Atlantis: 0.2 Ltr ha-1 + Puma Super: 0.312 Ltr ha-1 suppressed weed density of 70.9 m-2 and produced seed yield of 2162.5 kgs ha-1. It is noted that Hand weeding: 30 days after sowing showed weed density of 76.1 m-2 and seed yield 2042.5 kgs ha-1. The combined allelopathic plant applications of Sunflower +Bermuda grass extract each: 15 Ltr ha-1 reduced weed density 80.7 m-2 and obtained seed yield of 1923.2 kgs ha-1. Sole application of sunflower extract: 30 Ltr ha-1 resulted weed density 91.0 m-2 and recorded seed yield of 1804.2 kgs ha-1. Alone allelopathy application of Bermuda grass extract: 30 Ltr ha-1 noticed weed density 103.3 m-2 and produced seed yield of 1684.8 kgs ha-1. The highest weed density 140.9 m-2 and lowest seed yield 1343.1 kgs ha-1 noticed in weedy check treatment where no any application applied for weed reduction. According to irrigation frequencies the 4 watering applications resulted less weed density 82.2 m-2 and obtained maximum seed yield 1996.3 kgs ha-1 followed by 3 watering applications noted weed density 84.5 m-2 and achieved seed yield 1955.5 kgs ha-1. The maximum weed density 86.7 m-2 and lowest seed yield recorded in 2 watering application. The analysis of variance of pooled data revealed that Atlantis: 0.1 Ltr ha-1 + Puma Super: 0.156 Ltr ha-1 + Sunflower extract: 15 Ltr ha-1 integrated treatment under 4 watering applications (15, 30, 45 and 60 DAS) caused significant impact on weed inhabitation and yield enrichment

Influence of tillage systems and herbicides on weed control and yield of cotton in wheat-cotton system

Wheat–cotton system is a major production system in Pakistan, however, cotton yield is declining in the system most likely due to weeds infestation and intensive tillage practices. Conservation tillage such as reduced and zero tillage in combination with appropriate herbicide may have the potential to enhance cotton yield on sustainable basis. The objective of this study was to determine the effect of herbicides under different tillage systems on weed control and cotton yield in wheat-cotton system. A field experiment was conducted at Cotton Research Station, Ratta Kulachi, Dera Ismail Khan, Pakistan, during 2017 and 2018. In the experiment, post-emergence herbicides, i.e. floxyfop-R-methyl 10.8 EC (108 g a.i. ha-1), lactofen 24 EC (168 g a.i. ha-1), floxyfop 10.8 EC + lactofen 24 EC, hand weeding, weedy check and three tillage systems (zero tillage, reduced tillage and conventional tillage) were evaluated in randomized compete block design (RCBD), with split plot arrangements, replicated 4 times. Tillage was allotted to main plots while herbicides were applied to subplots. The results revealed that hand weeding and floxyfop as post emergence alone or in combination with lactofen reduced weed density to the minimum irrespective of the tillage systems. Maximum dry weed biomass was recorded in control. Interaction effects revealed that reduced tillage in combination with broad spectrum herbicides had maximum weed population reduction percentage. Reduced tillage with broad spectrum herbicides had seed cotton yield compared to zero and conventional tillage. In conclusion, broad-spectrum herbicides under reduced tillage were more productive in wheat based cropping system on silty clay soil of D.I.Khan.

Effects of plastic film mulching on soil quality, growth of Angelica sinensis, and weed occurrence in cold and humid areas

We analyzed the growth dynamic and bolting rate of Angelica sinensis, soil quality and enzyme activities and weed density and control effect in a field experiment under different mulching patterns, to provide theoretical basis for the application of plastic film in genuine producing area of A. sinensis. The planting patterns were conducted as hole seeding under ridging with plastic-film mulching (LS), trenching and slant planting under film-side cultivation (MC) and trenching and slant planting in open field (LD). Our results showed that, 1) compared with LD, soil organic matter content in top layer under the treatments of LS and MC was increased by 4.4% and 14.3%, respectively, with that under MC being statistically significant. Soil bulk density was significantly decreased by 11.6% and 8.5%, while pH was significantly decreased by 4.6% and 1.7%. The activities of soil sucrase, phosphatase and urease were significantly increased by the two mulching methods, but that of catalase was inhibited to a certain extent. 2) Mulching film improved the speed of returning green after transplanting, the early bolting rate, and the individual medicinal quality of A. sinensis. MC showed the fastest, the most uniform, and the highest greening rate. LS bolting rate was the highest, and the fresh mass of MC and LS was significantly increased by 20.4% and 58.4%, respectively. 3) Weed density under the treatment of MC and LS was significantly reduced by 34.0% and 25.8%. Compared with LS, MC significantly increased the control effect of plant and fresh mass by 21.7% and 63.4%, respectively. In conclusion, film cultivation methods could improve the environment for root growth, reduce weed density, improve weed control effect, and promote growth process and substance accumulation, but could promote the bolting of A. sinensis in early phase.

Rye (&lt;em&gt;Secale cereale&lt;/em&gt; L.) and squarrose clover (&lt;em&gt;Trifolium squarrosum&lt;/em&gt; L.) cover crops can increase their allelopathic potential for weed control when used mixed as dead mulch

Cover crops are essential tools in agro-ecosystems for reducing the reliance on synthetic inputs and associated environmental risks. Alongside their benefits to soil fertility, cover crops can control weeds by their competitive and allelopathic attributes. Laboratory and field experiments were conducted to assess the allelopathic potential of two cover crop species, rye (Secale cereale L.) and squarrose clover (Trifolium squarrosum L.), alone or in a mixture, on seed germination and growth of arable weeds. Aqueous extracts of the two cover crops and their mixture were tested in a bioassay on Conyza canadensis (L). Cronq., Amaranthus retroflexus L. and Digitaria sanguinalis (L.) Scop. In vitro effects of aqueous extracts varied in a dose-dependent manner, with cover crops and weed species. All three extracts were able to reduce the germination of A. retroflexus (–87%) considerably. Inhibitory effects by rye and mixture extracts on radicle growth of all weed species ranged between 51 and 82%. Rye extract was the best at reducing shoot length of C. canadensis and D. sanguinalis (–39 to 44%), while squarrose clover was more effective on A. retroflexus (–79%). Plant extracts also delayed the germination time of weed species with a substantial effect of the mixture on C. canadensis seeds. In the field experiment, no significant weed suppression was provided by cover crop residues incorporated as green manure compared to control plots, despite tillage being more effective in reducing weed density than no-till. Still, the mulch of the mixture controlled weed emergence significantly better than single cover crop mulches. The chemical characterization of cover crop residues, both shoots and roots, revealed a notable richness of allelopathic phenolic acids and flavonoids, which may constitute potential natural herbicides through slow decomposition. From the analysis of the aqueous extracts, other non-analysed and/or unidentified water-soluble allelopathic compounds should underlie the phytotoxicity observed in vitro, at least for rye. For cover crop mixture, positive interactions among plant materials leading to a better release of allelochemicals and weeding effectiveness are discussed according to chemical profiles and field data. Our study demonstrated the allelopathic activity of the cover crops and their potential to be included in weed management strategies according to cropping system needs. Additional trials are needed to confirm the performance of cover crop residues under field conditions. Highlights - Rye and squarrose clover are cover crops with potential allelopathic effects. - Aqueous extracts of residues of rye, squarrose clover, and their mixture reduced and/or slowed weed germination of A. retroflexus and C. canadensis in the in vitro bioassays. - Depending on the concentration of residues, the aqueous extracts had inhibitory effects on radicle and shoot growth of A. retroflexus, C. canadensis, and D. sanguinalis. - The mulch of a mix of rye and squarrose clover under field conditions suppressed weeds better than the single species.

Effects of band steaming on weed control, weed community diversity and composition and yield in organic carrot at three Mediterranean sites

AbstractBand steaming is a non‐chemical weed control method of increasing interest for highly remunerative, low competitive crops. This study aimed to test the field application of a new prototype of band‐steaming machine in three organic fields under contrasting Mediterranean environmental conditions. Trials were conducted in carrot under real‐field conditions to investigate the effects of three steaming doses and one control (no steaming) on weed vegetation and crop yield. Soil temperature at steaming application, weed density at species level during carrot crop growth, and weed and carrot biomass at harvest were sampled at each site. Band steaming significantly affected total weed density: when comparing the untreated control with the highest steam dose, weed density reduction ranged from 62% (−492 plants m−2) at site II to 94% (−146 plants m−2) at site III. Generally, diversity of weed communities decreased with increasing steaming dose, indicating a progressive species filtering effect: Fumaria officinalis L. and Sonchus oleraceus L. were filtered by steaming application at site I, while Polygonum lapathifolium L. and Portulaca oleracea L. were filtered at sites II and III. Weed community composition was affected by steaming dose at two sites out of three. Small seeded species (seed mass &lt;1.5 mg) were less tolerant of steaming than species with large seeds. Through reduction in weed density, steam application gave carrot a competitive advantage, increasing fresh yield from 47% at site III (+3,646 g m‐2) to 92% at site II (+1,866 g m‐2), compared with yields at non‐steamed plots.

Weed Management of Kenaf (Hibiscus Cannabinus) Through Intercropping Leafy Vegetables And Cultural Practices

A field experiment was conducted at Jute Research Experimental Station, Manikganj, Bangladesh during 2017 and 2018 cropping seasons to study the feasibility of intercropping leafy vegetables at early stage of the fibre crop: kenaf along with conventional weeding methods for better weed suppression and higher productivity. A Randomized Complete Block Design (RCBD) was followed consisting of eight treatments with three replications. Three leafy vegetables: red amaranth, jute shak and kangkong were used as intercrop with kenaf following 1 hand weeding and 1 hand hoeing alternately. Sole kenaf (weeded twice) was also grown as control. The total weed vegetation was comprised of grasses 49%, broadleaved 33% and sedge only 18%. Performance of kangkong as intercrop was found better in terms of weed suppression. Hand weeding was found more efficient as a cultural weeding method in reducing weed density. Although intercropping resulted in significant yield reduction of kenaf but increased net return and benefit-cost ratio (BCR) by increasing kenaf equivalent yield (KEY). The land equivalent ratio (LER) was found higher in all intercropping treatments than sole kenaf which indicated more efficient utilization of land under intercropping. Red amaranth intercropping+1 hand weeding resulted the maximum gross return (TK.1,36,200 ha-1) while the highest gross margin (Tk. 59,390 ha-1) and BCR (1.78) was obtained from jute shak intercropping+1 hoeing. Considering the production cost, monetary return and productivity, Kenaf intercropped with Jute shak+1 hoeing was found better than other intercropping treatments. SAARC J. Agric., 19(1): 165-176 (2021)