Predominant Weeds Research Articles

Productivity of summer greengram (Vigna radiata) under different nitrogen levels and weed management practices

A field investigation was carried out during summer season, 2022 at ARS, Faculty of Agricultural Sciences, SOADU, Bhubaneswar to study the effect of nitrogen levels and weed management practices on Weed growth and productivity of summer greengram (Vigna radiata L.). The experiment was laid out in split plot design with three replications comprising fifteen treatment combinations. Treatments consisted of three nitogen levels in main plot and five weed management practices in subplot. The predominant weeds in the experimental plots were Poa annua, Digitaria sanguinalis, Echinochloa colona, Cleome viscose, Ageratum conyzoides, Portulaca oleracea, and Melochia corchorifolia. Results revealed that among the different levels of nitrogen, the lowest density and dry weight of grasses, broadleaved and total weeds was recorded with application of 75% N. Among the weed management practices, two hand weeding at 15 and 30 DAS, registered significantly lowest density and biomass of all categories of weeds as well as total weeds and it was closely followed by pre-emergence application of ready-mix pendimethalin + imazethapyr 0.75 kg/ ha at 45 DAS. Application of 125% N registered highest seed (832.30 kg/ ha) and stover yield (2189.64 kg/ ha) and along with high yield attributing characters like number of pods/ plant (25.54) and seeds/ pod (6.39) as compared to others and it was at par with application of 100% N. Among the weed management practices, two hand weeding at 15 and 30 DAS recorded highest seed yield (930.56 kg/ ha) and stover yield (2397.11 kg/ ha) of greengram along with higher yield attributing characters like number of pods/ plant (27.73), seeds/ pod (7.29) and number of branches/ plant (8.94) and it was closely followed by pre-emergence application of ready-mix pendimethalin + imazethapyr at 0.75 kg/ ha.

Weed dynamics, energetic, yields and economics as influenced by sequential application of herbicides for weed management in direct seeded rice

This study quantifies the crop yield loss by weeds and management of hardy and prominent weeds. Uncontrolled weeds reduced grain yield of DSR by 68%. Pendimethalin 1.0 kg ha−1 pre-emergence (PE) followed by (fb) bispirbac-sodium 30 g ha−1 at 25 DAS fb fenoxaprop-p-ethyl 60 g ha−1 at 30 DAS, and pendimethalin 1.0 kg ha−1 (PE) fb azimsulfuron 25 g ha−1+fenoxaprop-p-ethyl 60 g ha−1 at 30 DAS significantly reduced weed density and weed dry matter, and recorded higher grain yield in DSR than other treatments. The pendimethalin 1.0 kg ha−1 (PE) fb bispyribac-sodium 30 g ha−1 at 30 DAS was statistically similar to stale seed-bed fb bispyribac-sodium 30 g ha−1 at 30 DAS and gave higher weed control efficiency and energy index compared to unweeded control and bispyribac-sodium 30 g ha−1 at 30 DAS. Pendimethalin 1.0 kg ha−1 (PE) fb bispyribac-sodium 30 g ha−1 at 25 DAS fb fenoxaprop-p-ethyl 60 g ha−1 30 DAS showed more promising in controlling tough weeds like L. chinensis and D. aegyptium and predominant weeds (Echinochloa colona, broad-leaved weeds and Cyperus species) in DSR.

Efficacy of Pre and Post Emergence Herbicides against Complex Weed Flora, Yield and Economics of Blackgram under High Hills Wet Temperate Zone of Himachal Pradesh

Background: Implementing integrated strategies for weed management is essential in maximizing blackgram yield. Unchecked weed proliferation leads to substantial decrease in crop productivity. Methods: The current field experiment was conducted at Salooni, Himachal Pradesh, to evaluate the efficacy of different integrated weed management practices during Kharif 2022 and 2023. Eleven treatments targeting weed control were evaluated both at pre and post - emergence stages. Result: The predominant weeds were Echinochloa colona, Galinsoga parviflora, Cyperus species and other broad leaf weeds were Plantago lanceolata, Trifolium repens, Trianthema species, Ageratum conyzoides. Data on weed dynamics revealed that; after weed-free treatment, the application of Imazethapyr 75 g/ha as PE fb HW at 30 DAS; Pendimethalin 1.0 kg/ha as PE fb HW at 30 DAS and Pendimethalin 1.0 kg/ha + imazethapyr 75 g/ha (PE) recorded a significantly lower total weed count as compared to other treatments. Parameters related to blackgram growth and yield, including plant height, number of branches per plant, pods per plant, grain yield and haulm yield were significantly higher with weed-free treatment followed by application of imazethapyr 75 g/ha as PE fb HW at 30 DAS, remaining at par with application of pendimethalin 1.0 kg/ha + imazethapyr 75 g/ha (PE) and pendimethalin 1.0 kg/ha as PE fb HW at 30 DAS. The most economically efficient weed control method was the combination of pendimethalin 1.0 kg/ha + imazethapyr 75 g/ha (PE), as it resulted in the highest net returns and marginal benefit-cost ratio.

Species composition of perennial weeds as influenced by mechanical steam treatment

Despite the great aspect of the use of chemical agents for plant protection against weeds, it is not always 100% commensurate with preparations. Since each plant develops immunity to drugs over a period of time, thus many agricultural producers strive to improve and find new methods of destroying parasites harming plants. Modern agricultural production reasonably puts forward the requirements for increasing the profitability and environmental safety of the products obtained. In this regard, there are great opportunities for the effective use of mechanical and physical methods of weed control, instead of problematic options for the use of herbicides. The improvement of tillage systems, in terms of greening agriculture, is primarily associated with their adaptation to a variety of soil and climatic conditions and in-depth differentiation in accordance with the agro-ecological requirements of crops. An optimally selected tillage system maintains a favorable phytosanitary condition of the soil for plants. Based on previous research in this area, the experience was studied and referred. The article presents the results of the number of treatments for the predominant weeds in the Southern Federal District of the Russian Federation. Taking into account early studies, it was revealed that due to the increased share of grain crops in the crop rotation, the amount of weed vegetation in the field increases over the years. We chose the chisel treatment method by the working bodies of the "Ranch" with a reservoir turnover of 0.12-0.15 m. When taking into account the clogging, the methods of A.M. Tulikov were used. There is a noticeable reduction in the contamination of certain plant species in all the years of the study for 2020-2022. Therefore, the goal was set to study each type of weed vegetation after cultivations prevailing in the Southern Federal District. The results were reliable and complete. By carrying out multiple cultivations, it was possible to identify weed vegetation most susceptible to processing by chisel organs of the "RANCH" without the introduction of chemical means of protection.

Efficacy of Herbicides on Weed Control & Growth Parameter on Wheat

Wheat (Triticum aestivum) is a globally significant crop and a staple food for millions of people. Weed infestation is one of the major constraints affecting wheat productivity worldwide. The purpose of this study was to assess the efficiency of Carfentrazone ethyl 5% + Clodinafop propargyl 15% DF as a post-emergence herbicide against predominant weeds in wheat crops. Wheat is a globally significant crop and a staple food for millions of people. Weed infestation is a major constraint affecting wheat productivity. The study was conducted using a Randomized Block Design with three replications and a total of 11 treatments. The herbicide treatments were applied using foliar spray at different doses. Weed control efficiency was evaluated at 30, 45, and 60 days after herbicide application.
 The results showed that the highest weed control efficiency was observed in the weed-free plot, followed by the treatment with Carfentrazone ethyl 5% + Clodinafop propargyl 15% DF at a dose of 800 g/ha. This treatment provided significant control against different weed species such as Phalaris minor, Avena ludoviciana, and Chenopodium album. The herbicide treatments showed varying degrees of control efficiency, with some treatments performing better than others.
 These findings highlight the importance of weed management for increasing wheat crop production. The judicious use of herbicides, such as Carfentrazone ethyl 5% + Clodinafop propargyl 15% DF, can effectively control weeds and contribute to higher yields. However, further research and field trials are necessary to optimize the herbicide application and determine its long-term effects on wheat crops. Overall, this study emphasizes the need for effective weed control strategies to enhance wheat productivity and meet the demands of a growing population.

Effect of polyethylene sheet colour and in situ solarization durations on the phytosociological structures of the predominant weeds in humid environment of southern Nigeria.

High humidity favours the proliferation of a wide range of weed species. Studying the phytosociological attributes of weeds in a humid area provides insight into the dynamism and relative importance of each weed species peculiar to the area which is very important in understanding crop-weed interrelationships and highlights the bases for effective management stratages. An experiment was conducted in 2019 and 2020 cropping seasons at the Department of Crop Science Teaching and Research Farm, University of Calabar, to identify the predominant weeds in the farm area and assess their responses to polyethylene colour and soil solarization duration. The experiment was a factorial combination of two polyethylene colour (black and transparent) and five in situ soil solarization durations (0, 8, 12, 16 and 48 weeks), laid out in randomized complete block design (RCBD) with three replications. Data were collected on the phytosociological characteristics of the weeds on four weekly intervals up to the twentieth week. The predominant weeds identified in the experimental area were Eragrostis ciliaris L., Cynodoon dactylon L., Panicum maximum Jacq., Axonopus compressus Beav., Kyllinga bulbosa Beav. and Kyllinga erecta Schum., Gloriosa superba L., Ipomoea involuncrata P., Calapogonium mucunoides Desv., Aspillia bussei O. Hoff, Ageratum conyzoides L., Phyllantus amarus Schum., Caldum bicolor Vent., Triumfeta rhomboidea Jacq., Cleome rutidosperma DC., Euphorbia heterophylla L., Mitracarpos villosus DC., Oldenladia. herbacea L. The relative density of Caladum bicolor was higher across the treatment in both years, reaching up to 37.7 % in the plot solarized for 16 weeks using black polyethylene, followed by P. maximum with upto 18.40 % in 2019 and Gloriosa superba (20.50 %) in 2020. The highest Important Value Index was recorded by Caladum bicolor reaching up to 28.7 % in the plot solarized for 16 weeks using black polyethylene. The lowest species variation was recorded in the plots solarized for 16 to 48 weeks irrespective of the polyethylene colour. In situ solarization of up to sixteen weeks using black polyethylene effectively controlled majority of the weed species in both years and is recommended for effective weed suppression in cassava farms in humid environment.

WEEDS INFESTING WHEAT CROP IN ROHTAK, HARYANA

Multiple field visits were performed to investigate weed flora of wheat fields in Rohtak district of Haryana, conducted during 2018 which revealed infestation of 28 weed species comprising 15 families of grasses and broadleaf weeds.The weeds were identified with the help of available literature and through comparison with the already identified weed species. Poa annua, Polypogon monspeliensis and broadleaf weeds Chenopodium album, Rumex retroflex, Coronopus didymus were the pre-dominant weeds in moist region, whereas Cynodon dactylon, Fumaria parviflora, Chenopodium album,Polypogon monspeliensis in light soil with low salinity.There was a greater variety of weeds in Bohar and Kharawar villages and the least was found in village Sheria and Garnavati from vegetative to fully grown stage.Maximum number of species were of family Poaceae and Asteraceae. This study will be helpful as an additional tool in maintaining the floristic composition of District Rohtak as well as in controlling the weed problem.

Hot foam: Evaluation of a new, non-chemical weed control option in perennial crops

Hot foam applications represent a new, smart concept in the field of thermal weed control. The aim of this study was to evaluate the efficacy of hot foam and other weed control methods in two olive groves in southern Greece (Pyrgos and Kalamata). The experiment was laid out in a randomized complete block design (RCBD) with six treatments and three replicates. Treatments were applied in the areas between trees, in the row and included mowing with a disc–flail mower, mulching with pruning residues (2.65 kg m–2), glyphosate (at 1,440 g a.e. ha–1), hot foam (13.33 L m–2), pelargonic acid (at 1,088 g a.i. ha–1; twice), and an untreated control. Two experimental runs were conducted at each site using the same treatment list. Malva parviflora L. and Sinapis arvensis L. were the predominant weeds in Pyrgos, while Urtica urens L., Galium aparine L., and Parietaria officinalis L. dominated in Kalamata. Site–experimental runs and treatments significantly affected NDVI and weed biomass (P–Value ≤ 0.001). Hot foam reduced weed biomass by up to 81, 88, 90, and 96% compared to mulching, mowing, pelargonic acid, and the untreated control, respectively. This treatment also reduced M. parviflora biomass by 75–88 and 92–93% compared to mowing and pelargonic acid, respectively, in Pyrgos and P. officinalis biomass by more than 80% in Kalamata compared to the above treatments. In all site–experimental runs, hot foam and glyphosate resulted in the lowest NDVI and weed biomass. The overall performance of hot foam was comparable to glyphosate, suggesting that this method is an environmentally friendly and effective, alternative method to control weeds in olive groves. Further research is required to optimize the use of hot foam for weed control in more perennial crops and under different soil and climatic conditions.

Efficiency of Certain Herbicides and Adjuvants Combinations Against Weeds in Wheat Fields

Two field experiments were carried out at El-Dalangat district, El-Beheira Governorate, Egypt during two successive winter seasons of 2017-2018 and 2018-2019, to evaluate the efficiency of post-emergence herbicides: Clodimex (clodinafop-propargyl 24% EC),Pallas (pyroxsulam 4.5% OD), Skylla (tribenuron-methyl 75% WG) at their recommended rates or at reduced rates without adjuvants or in combination with Argal at 0.2% v/v and Techno oil at 0.3% v/v adjuvants in combination with clodinafop-propargyl + tribenuron-methyl at half recommended rate combined with Argal or Techno oil adjuvants and hand weeding at 25 and 40 days after sowing (DAS) for controlling predominant weeds in wheat crop compared to unweeded check. The results indicated that the dominant weed species in the experimental wheat field were, two grassy weeds, Phalaris minor and Eragrostis ciliagensis, and six broad-leaved weeds: Malva parviflora, Sonchus oleraceus, Coronopus squamatus, Rumex dentatus, Anagallis arvensis and Medicago polymorpha during the both seasons. In addition, Eclipta alba weed was found only in the second season. Results also showed that all herbicidal treatments significantly decreased the total weed biomass compared to the unweeded check 60 and 90 DAS. Among herbicidal treatments applied, pyroxsulam herbicide at ¾ of recommended rate with Argal recorded the highest weed control efficiency against grassy and broad-leaved weeds followed by pyroxsulam treated plots at ¾ of recommended rate combined with Techno oil 60 and 90 DAS throughout the two studiedseasons. On the other hand, regardless of application rates or adjuvants, tribenuron-methyl and clodinafop-propargyl seemed to be the least effective treatments against the total weeds 60 and 90 DAS during the both seasons in comparison with unweeded plots. The maximum increase in wheat grain yield was observed in pyroxsulam treated plots at ¾ recommended rate with Argal or Techno oil combinations. It could be concluded that the addition of Argal or Techno oil to herbicides spray solutions at reduced rates especially at ¾ of the recommended rate resulted in enhancing the herbicidal activity against weeds and increasing wheat grain yield.

Study on effect of weed management practices on weed dynamics and productivity of kharif maize

Field trials were conducted at Agricultural College and Research Institute, TNAU, Coimbatore, Tamilnadu, India, during two consecutive kharif (rainy) seasons of 2018 and 2019. The experiment was laid in a randomized block design different weed control methods viz., pre emergence (PE) atrazine at 0.5 kg a.i. ha-1 fb hand weeding (HW) at 20 DAS, PE atrazine at 0.5 kg a.i. ha-1 fb power weeder (PW) at 20 DAS, PE atrazine at 0.5 kg a.i. ha-1 + pendimethalin at 1 kg a.i. ha-1 (Tank mix), PE atrazine at 0.5 kg a.i. ha-1 + pendimethalin at 1 kg a.i. ha-1 fb HW at 20 DAS, early post emergence (EPOE) topramezone at 25.2 g a.i. ha-1, PE atrazine at 0.5 kg a.i. ha-1 fb EPOE topramezone at 25.2 g a.i. ha-1, EPOE tembotrione at 122 g a.i. ha-1, PE atrazine 0.5 kg a.i. ha-1 fb EPOE tembotrione 122 g a.i. ha-1, hand weeding twice at 20 and 40 DAS and control (weedy check) with 3 replications for each treatment. The results revealed that the experimental field was infested with all categories of weeds including grasses, broad-leaved weeds and sedges. Among them the most predominant weeds were Cynodon dactylon, Dactyloctenium aegyptium, Echinochloa colona, Amaranthus viridis, Digera arvensis and Trianthema portulacastrum. Among the chemical weed control methods PE atrazine at 0.5 kg a.i. ha-1 fb EPOE topramezone at 25.2 g a.i. ha-1 and PE atrazine 0.5 kg a.i. ha-1 fb EPOE tembotrione 122 g a.i. ha-1 recorded significantly lower weed density as well as weed dry weight of BLW, grasses, sedges and total weed at 90 DAS during 2018 and 2019, respectively. As a consequence of effective weed control, the above treatments recorded significantly higher weed control efficiency (WCE) and lower weed index (WI) during 2018 and 2019, at 90 DAS. These treatments were statistically comparable with hand weeding twice at 20 and 45 DAS. Uncontrolled weed growth in control (weedy check) recorded higher weed density and weed dry matter in maize crop during both the years of experimentation.

Efficacy of fenoxaprop-p-ethyl and penoxsulam for weed management with special emphasis on Echinochloa spp. in transplanted summer rice

An on-farm experiment was conducted during summer (boro) season of 2016-17 at farmer’s field (Borah village of Nanoor Block) in Birbhum district, West Bengal to study the efficacy of fenoxaprop-p-ethyl and penoxsulam against composite weed flora with special emphasis on Echinochloa spp. in transplanted rice. The experiment comprising of eight treatments was laid out in a randomized block design with three replications. The experimental field was dominated with Echinochloa glabrescens, E. crus-galli, Panicum sp. (grasses), Cyperus iria (sedge) and Jussiaea repens (broad-leaved) throughout the crop growing period. Of these predominant weeds, there was severe infestation of grassy weeds. Among herbicidal treatments, fenoxaprop-p-ethyl 90 and 100 g/ha at 20 days after transplanting (DAT) and penoxsulam 25 g/ha at 20 DAT effectively controlled the Echinochloa spp. at 50 DAT. Application of penoxsulam 25 g/ha at 20 DAT exhibited effective management of composite weed flora as well as higher grain yield in summer rice. Lower values of weed density and weed dry weight along with improved weed control efficiency and higher grain yield were registered with penoxsulam 25 g/ha at 20 DAT, which was statistically at par with two rounds of hand weeding at 20 and 40 DAT in summer rice.

Efficacy of certain herbicides on broad-leaved weeds in wheat crop (Triticum aestivum L.)

Field experiments were carried out at Mutobus District, Kafr El-Sheikh Governorate to evaluate the efficacy of AckocynilR (bromoxynil octanoate 32.75% EC) at 1.00 L. fed-1, Brominal WR (bromoxynil octanoate 24% EC) at 1.00 L. fed-1, DerbyR (florasulam 7.5 %+ flumetsulam 10%) at 30 ml fed.-1, IcopartR (pyraflufen-ethyl 2% SC) at 250 ml fed.-1 and SinalR (metosulam 10% SC) at 40 ml fed.-1 in comparison with handweeding twice (at 21 and 42) days after sowing and untreated check (weed free) during 2017/2018 and 2018/2019 seasons on broad-leaved weeds in wheat crop. Anagallis arvensis, Beta vulgaris, Cichorium pumpilum, Medicago sativa, Rumex dentatus and Sanchus oleraceus, were the predominant weed species during the both seasons, except, Anagallis arvensis, which was found in the second season only. All predominant weeds in the experimental field were identified as broadleaved weeds. Among predominant weed species, Beta vulgaris and Medicago sativa were the most predominant during 2017/2018 and 2018/2019 seasons. Results clearly indicated that all herbicidal treatments showed significant herbicidal activity against weeds compared to the control during the two examined seasons. Among the herbicides examined, AckocynilR and Brominal WR were the most options in controlling weeds as well as increasing yield components and grain yield in wheat crop than the other treatments.

Replace of the EPOST glyphosate with pre herbicides and application of different LPOST glyphosate rates for weed control in established vineyard

Two-year field trials were conducted at two winegrowing districts (Kavadarci and Skopje in 2016 and 2017) to evaluate wheather oxyfluorfen, pendimethalin and flazasulfuron can replace early post-emergence (EPOST) application of glyphosate in established vineyard until its application in early summer period. The weed vegetation in vineyards in both years was consisted mainly of Chenopodium album L., Setaria viridis (L). Beauv., Papaver rhoeas L., Xanthium strumarium L., Lolium multiflorum Lam., Sorghum halepense (L.) Pers. and Cynodon dactylon (L.) Pers. Pendimethalin, oxyfluorfen and flazasulfuron efficiently reduced predominant annual weeds and S. halepense seedlings in 2017, but not in 2016. PRE herbicides, regardless year, had no significant effect on C. dactylon. Opposite, the efficacy of EPOST applied glyphosate was significantly lower in 2017 compared to 2016. LPOST glyphosate applied at 2.0 l ha-1 provided at least 94 % control of dominant annual broadleaf and grass weeds. LPOST application of glyphosate at 2.0 l ha-1 and glyphosate at 2.0 and 4.0 l ha-1 resulted in unsatisfactory weed control of predominant perennial S. halepense, and C. dactylon, respectively. LPOST glyphosate applied at 4.0 l ha-1 provided control of S. halepense by 84 % or more. LPOST glyphosate applied at 8.0 l ha-1 reduced the amount of S. halepense and C. dactylon at least 97 %. Grapevine yield of both varieties was not lower in all herbicide treatments in 2016 compared with 2017. However, yield in the PRE herbicide treatments fb 2.0 and 4.0 l ha-1 glyphosate was collectively 15-19 % and 17-19 % lower compare to PRE herbicide treatments fb 8.0 l ha-1 glyphosate and standard two applications of glyphosate, respectively for both years and districts. No impacts to grapevine growth were observed from PRE herbicide treatments at either district

Effect of integrated weed management practices on growth and yield of Direct Seeded rice under puddle condition of Agro-climatic situation of Chhattisgarh

The present investigation was conducted at Instructional Farm of Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.) India during the kharif season (June-October) 2006. The experiment was laid out in randomized block design comprised of eight treatments of various combinations of different herbicides viz. T1:PIH 2023 10% SC 15 g a.i/ha at 18 DAS; T2 : PIH 2023 10% SC 20 g a.i/ha at 18 DAS; T3 : PIH 2023 10% SC 25 g a.i/ha at 18 DAS; T4 : PIH 2023 10% SC 30 g a.i/ha at18 DAS; T5 : PIH 202310% SC 60 g a.i/ha at 18 DAS T6 : Almix 20% WP 4 g a.i/ha 18 DAS; T7 :Control (unweeded check) and T8 : Hand weeding at 30 DAS with three replications. Rice cultivar “IR-64” was grown as a test crop. The growth performance of Rice i.e. plant height, Number of tillers(m-2), Number of effective tillers(m-2), dry matter accumulation plant-1, was higher under PIH 2023 10% SC 25 g a.i/ha as compared to other weed management practices. Wher as the minimum growth of rice recorded under unweeded. Maximum grain yield and straw yield was under PIH 2023 10% SC 60 g a.i/ha Echinochloa colona, Cyperus spp., F. miliaceae, L. hyssopifolia were the pre-dominant weeds in experimental plot. Minimum weed density was noted under post emergence application of Almix 4 g ha-1 and PIH 2023 25 g ha-1 at 20, 40, 70 and 90 DAS. Whereas, at harvest lower dry matter of weeds and highest weed control efficiency was recorded under Almix 4 g ha-1 (T6), PIH 2023 25 g ha-1 and PIH 2023 60 g ha-1, respectively. It was found effective to control broad spectrum of weeds viz., grasses, sedges and forbs.

Changes in the Weed Seed Bank in Long-Term Establishment Methods Trials under Rice-Wheat Cropping System

The rice–wheat cropping system in the Indo-Gangetic Plains is the backbone of food security in India. In the 1990s, due to the scarcity of resources, the traditional Crop Establishment (CE) method shifted from Conventional Till Puddle Transplanted Rice (CTPTR) to CT Direct Seeded Rice (CTDSR) and Zero-Till DSR (ZTDSR) in paddy; and in wheat, from Conventional Till Wheat (CTW) to Zero Till Wheat (ZTW), with residue retention in rice (RRR) or in both rice and wheat (RRRW). Shift in CE methods led to change in Weed Seed Bank (WSB) dynamics and ultimately affected the weed management program. After five years of field trials, soil samples were drawn as per 2-factors factorial randomized block design. Factor-I comprised 4-CE methods, whereas factor-II consisted of 3-soil depths (0–10, 10–20 and 20–30 cm). Results showed CTPTR-CTW and ZTDSR-ZTW (RRRW) record the highest seed bank (SB) of grasses, sedges and BLWs as total weeds, in general; and predominant weeds like Echinochloa spp., Ammania baccifera, Commelina benghalensis and Digitaria sanguinalis, in particular. It also showed the higher species richness (DMg) and Shannon–Weaver (H’) indices. CTDSR-CTW and CTDSR-ZTW (RRR) show the lowest WSB and at par with Shannon–Weaver (H’) index; further, lowest species richness (DMg) under CTDSR-CTW. Species Evenness (J’) and Simpson index (λ) vary non-significantly with CE methods. Furthermore, 0–10 cm soil depth showed the highest SB of different category of total weed, predominant weeds as well as higher values of DMg, H’, and λ; whereas reverse trend was observed in Whittaker Statistic (βW). Interaction between CE methods and soil depth revealed most of WSB lying on the top layer in case of ZTDSR-ZTW (RRRW) and CTDSR-ZTW (RRR); while CTPTR-CTW showed almost uniform WSB distribution, and in case of CTDSR-CTW, a gradual decrease in WSB with soil depth.

Effect of herbicides on feeding, survival and development of Haltica cyanea, a biocontrol agent of dicot weed, Ammania baccifera L. in rice ecosystem

Ammania baccifera L. (Fam: Lathyraceae) is one of the predominant weeds in paddy fields. In nature, the adults and grubs of Haltica cyanea (Coleoptera: Chrysomelidae) feed varaciously on the leaves of this weed leading to drying of the plants. In recent times with the gradual change in cultivation practices and increase in labour shortage the use of weedicides in rice ecosystem has increased tremendously. In an endeavour to explore the possibility of the use of these beetles as biocontrol agents, laboratory studies were carried out at ICAR-IIRR to compare the efficacy of H. cyanea as a biocontrol agent in comparison with the two recommended herbicides and also study the effect of these herbicides on the biology of the beetle. The two recommended herbicides, 2,4-D Na salt 80% (for broadleaved weeds) @800g a.i/ha and Metsulfuron methyl 10% + chlorimuron ethyl 10% WP (for broadleaved and sedges) @4ga.i/ha were tested against A. baccifera and the larval stages of H. cyanea . The effect of these herbicides on survival, feeding, longevity and biology of the bioagent was studied through leaf dip and pot spray method. It was observed that there was 21.67% reduction in shoot weight in beetle released plants as compared to herbicide treatment wherein 38.5-49.3% reduction in shoot weight was observed within 48h. Both the herbicides affected the biology of the insect and between the two herbicides, 2,4-D Na salt was more toxic to the grubs as compared to Metsulfuron methyl + chlorimuron ethyl.

English

In order to identify combinations of effective preemergent herbicides for weeds in sugarcane, an experiment was conducted at the Agricultural School of Concepción; Concepción, Paraguay. The experimental model was subdivided plots, with two factors: A1 without herbicide for broadleaf weeds, A2 diuron (dose 3 t ha-1), A3 atrazine (dose 4 kg ha-1), A4 sulfentrazone (dose 1.2 t ha-1) and B1 without herbicide for weeds, B2 trifluralin (dose 3 l ha-1), B3 acetochlor (dose 1 l ha-1), forming twelve treatments with three repetitions. They were applied in preemergence, where the evaluations were from 20 to 41 days after application (DDA), for: degree of control, residual effect and control of predominant weeds. The combination of diuron and acetochlor, produced high weed control (more 90% up to 41 days DDA), being superior to the other treatments. Sida spp was better controlled with diuron; whereas Mollugo verticillata was effectively controlled with most combinations; Ipomoea nil was more sensitive to sulfentrazone, while; Cenchrus echinatus was effectively controlled, with the combination of diuron plus acetochlor. It is concluded that with the combination of diuron and acetochlor, a large variety of weeds was controlled and the highest residual effect was recorded. In addition, atrazine combined with graminicides (trifluralin or acetochlor) or diuron with acetochlor, provided total control of weeds. It is recommended: for Sida spp. diuron with acetochlor or atrazine. For Mollugo verticillata, sulfentrazone alone or combined with graminicides. Ipomoea nil, sulfentrazone. Cenchrus echinatus, diuron and acetochlor combined. Key words: Saccharum officinarum, weeds, preemergence herbicides.  

Tank mix application of tembotrione and atrazine to reduce weed growth and increase productivity of maize

The experiment was carried out during Kharif (wet) season of 2014 at Agricultural Farm of Palli Siksha Bhavana, Visva-Bharati, Sriniketan, West Bengal to find the effect of tank mix application of tembotrione and atrazine on weed growth and productivity of Kharif maize. Nine treatments comprising of herbicide tembotrione as early post-emergence at 80, 100, 120 g/ha alone and in combination with atrazine at 500 g/ha, sole application of atrazine at 1000 g/ha and weeding twice at 25 and 40 DAS and unweeded control were assigned in a randomized block design in three replication. Results revealed that the experimental field was infested with all categories of weeds including grassy, broad-leaved and sedges. Among them the most predominant weeds were Ludwigia parviflora, Cynodon doctylon, Cyperus rotundus and Fimbristylis miliacea. Overall weed infestation caused about 48% reduction in yield of maize. Combined application of tembotrione with atrazine was significantly superior to its sole application in all the doses tested. Tembotrione at 100 g/ha + stefes mero surfactant at 733 g/ha + atrazine 500 g/ha considerably reduced the weed infestation-registering lower weed density, dry weight, weed index, higher weed control efficiency and increase in values of growth and yield attributes and yield of maize, which were comparable with tembotrione at 80 g/ha + stefes mero surfactant at 733 g/ha + atrazine 500 g/ha and tembotrione at 120 g/ha + stefes mero surfactant at 733 g/ha + atrazine 500 g/ha. Thus, early post-emergence application of tembotrione at 80–100 g/ha + stefes mero surfactant at 733 g/ha + atrazine 500 g/ha appeared to be the most promising weed management practice for higher weed control efficiency, yield, gross and net return of Kharif (wet) season maize in lateritic soil of West Bengal.

Allelopathic effects and weed suppressive ability of cover crops

Field and laboratory experiments were conducted to investigate the weed suppressing effects of cover crops in single and mixed cultivation. Weed densities in the field experiments ranged from 0 to 267 plants/m2 with Chenopodium album L., Matricaria chamomilla L., Stellaria media (L.) Vill. as predominant weeds. It was found that mustard (Sinapis alba L.), fodder radish (Raphanus sativus var. niger J. Kern) and spring vetch (Vicia sativa L.) supressed weeds by 60% and cover crop mixtures controlled weeds by 66% during the fallow period at three experimental locations in 2013, 2014 and 2015. The biochemical effect of the same cover crops/mixtures on weed growth was analysed in laboratory experiments. Aqueous cover crop extracts were applied on weeds and analysed using LC/MS/MS. Mean germination time, germination rate and root length of weeds were determined. Extracts prolonged the germination time by 54% compared to the control with only water. In all cases, inhibitory effects on germination rate and root length were measured. Weed density in the field was found to be correlated with the root length in the germination tests. Our work reveals that biochemical effects play a major role in weed suppression of cover crops.

Winter oilseed rape and weed competition in organic farming using non-chemical weed control

One of the reasons why the area sown with oilseed rape in organic farms is not expanding is problems with weed, disease, and pest control as well as low seed yield. There is a lack of investigations on oilseed rape cultivated in an organic system, especially employing innovative weed control methods. To fill this gap in knowledge, field experiments were conducted at the Experimental Station of Aleksandras Stulginskis University in 2012–2013 with the aim of identifying and assessing the impact of different non-chemical weed control methods (thermal – TWC, mechanical – MWC and smothering – SMT) on weed competitiveness in winter oilseed rape (Brassica napus L.) crops during the autumn vegetation period in an organic farming system with and without the use of plant bio-activators in a soil with a regular (23–25 cm) (1st experiment) and with a thickened (48–50 cm) (2nd experiment) humus layer. It was found, that compared with thermal and mechanical weed control, in the treatment using smothering weed control and spraying with plant bio-activators or not spraying, the density of winter rape crop in the soil with a regular humus layer was significantly (P ≤ 0.05) lower (1.2 to 5.3 times); in the soil with a thickened humus layer, the density of winter rape crop was 1.5 to 5.9 times lower. In winter oilseed rape during autumn vegetation period, 20–22 weed species were found, including 18–19 annuals. Stellaria media (L.) Vill., Veronica arvensis L., Sinapis arvensis L. and Capsella bursa-pastoris (L.) Medik. were the predominant weeds. In the soil with a regular and a thickened humus layer, thermal and mechanical weed control significantly (P ≤ 0.05) decreased the number of weed seedlings (1.1 to 1.9 times) when plant bio-activators were used compared with the smothering treatment. Weed control in the smothering treatment in the soil with a regular and thickened humus layers was not effective. Mechanical weed control was more efficient than thermal. Application of plant bio-activators increased the efficiency of the thermal weed control.