Efficient Weed Management Research Articles

Efficacy of various herbicides for weed management in irrigated chickpea (Cicer arietinum)

Chickpea is a short-stature crop with slow initial growth and limited leaf area development due to which it is heavily infested with a wide spectrum of weeds. The menace of weeds has increased to such an extent that an ef- fective weed management schedule has become a necessity. A research study was conducted during the rabi season of 2021–22 at the Agronomy Research Farm, Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana. Thirteen weed control treatments viz., pre-plant incorporation (PPI) and pre-emergence (PRE) pendimethalin at 1,000 g/ha, PPI imazethapyr at 75 g/ha and 100 g/ha, PRE imazethapyr at 75 g/ha and 100 g/ha, post-emergence (PoE) imazethapyr at 75 g/ha and 100 g/ha, PPI and PRE pendimethalin + imazethapyr Ready mix (RM) at 1,000 g/h and two hand hoeings at 30 and 50 DAS were compared with weedy check and weed free in a randomized block design and replicated thrice. Among the herbicides, lowest weed dry weight was observed un- der PPI and PRE pendimethalin + imazethapyr (RM) at 1,000 g/ha respectively. PoE application of imazethapyr displayed phytotoxicity symptoms like stunting, leaf crinkling, and chlorosis as indicated by phytotoxicity scale ranging from 1-5. Significantly higher seed yield was obtained by pendimethalin + imazethapyr (1,827 kg/ha) over other combinations. Therefore, the PRE-application of pendimethalin + imazethapyr (RM) at 1,000 g/ha was the most suitable herbicide for efficient weed management in chickpea as it not only controlled the diverse weed flora but also improved seed yield.

Effect of chemical weed management on growth, yield and economics of drum seeded rice (Oryza sativa)

Field experiment was conducted at Periyanarkunam, Bhuvanagiri Taluk, Cuddalore District during Kuruvai 2021 and 2022 to study the effect of different herbicidal weed management on growth, yield and economics of drum seeded rice (Oryza sativa L.) variety ‘ASD 16’. The experiment was conducted in randomized block design with four replications. The treatments comprised of six weed management practices and are made up of a combination of herbicides (pre-emergence, early-post and post-emergence herbicides) with hand weeding, which was com- pared with unweeded control and twice hand weeding on 25 and 45 DAS. Application of bensulfuron methyl 0.6% + pretilachlor 6% GR @ 660 g a.i./ha PE fb metsulfuron methyl 10% + chlorimuron ethyl 10% WP @ 4 g a.i./ha PoE on 25 DAS fb hand weeding on 45 DAS recorded the highest weed control efficiency of 77.55 and 74.23% during Kuruvai 2021 and 2022 respectively, growth attributes at 60 DAS viz., plant height (96.82 and 91.79 cm), tillers/m2 (367 and 343) and dry matter production (8.01 and 7.78 t/ha), yield attributes like productive tillers/m2 (319 and 312), filled grains/panicle (100.64 and 98.42), grain yield (6.19 and 6.11 t/ha) and benefit cost ratio (2.78 and 2.49) during Kuruvai 2021 and 2022, respectively over bispyribac sodium 10% SC @ 25 g a.i./ha PoE on 20 DAS fb hand weeding on 45 DAS (farmers practice). Hence, it is an efficient weed management practice and an economically feasible method for achieving the maximum growth, yield and economics of drum seeded rice.

Advances in ground robotic technologies for site-specific weed management in precision agriculture: A review

Robotics and variable rate technology (VRT) have shown great potential for site-specific weed management (SSWM), but these technologies face several challenges like accurate weed identification, high initial cost, integration with existing farming practices, and the need for the development of precise and robust system for real-time application. Given the lack of comprehensive information on the current state of robotic technologies for weed management, this review study aims to provide an extensive overview of the individual components associated with SSWM technologies, such as autonomous navigation, imaging sensors, and weeding approaches. To perform this study, 91 technical papers were selected that involve the status, challenges, and potential improvements of individual components integrated to develop an efficient weed management technology. The key outcomes can be summarized as: (a) real-time kinematic-enabled global positioning system (RTK-GPS) and machine vision guidance systems are widely adopted technology for automatic row guidance because of their low cost, high accuracy, and easy accessibility, (b) GPS technology face challenges due to signal interference and dependency on satellite availability for accurate positioning, (c) sensor fusion has been suggested as a potential solution to improve the accuracy of positioning and weed identification, (d) deep learning techniques for weed identification offer significant promise in enhancing the feasibility of implementing robotic weed control in real-time, (e) due to robust nature of hyperspectral imaging, research in weed identification for real-time in open-field conditions is still lagging, (f) plethora of university-based research studies are limited to model optimization and simulation studies, and (g) integrated weed management practices, such as a combined application of mechanical and laser weeding, could be the future of robotic weed control. This review will serve as a valuable reference to extension educators, growers, researchers, and stakeholders for adopting state-of-the-art and sustainable practices in SSWM.

Influence of sowing dates and weed management practices on weed dynamics, productivity and profitability of direct seeded rice

This study evaluated the impact of differential sowing windows and improved weed management strategies on weed dynamics, productivity, and economic viability of direct drum seeded rice (Oryza sativa L.) in the temperate agro-ecosystem of Kashmir. A two-year field experiment was conducted utilizing a split-plot design with two sowing dates (May 10 and June 3) as main plots and six weed management practices as sub-plots. The earlier sowing date (May 10) resulted in significantly enhanced leaf area index, crop growth rate, relative growth rate, net assimilation rate, and grain and straw yields compared to the later sowing (June 3). Among weed management treatments, four mechanized conoweedings (equivalent to weed-free conditions) and sequential application of bensulfuron methyl + pretilachlor (60 and 600 g a.i. ha−1) as pre-emergence followed by 2,4-D (0.75 kg a.i. ha−1) as post-emergence demonstrated superior efficacy in weed suppression and augmentation of crop growth parameters and yield attributes. These treatments also exhibited the lowest weed index and highest benefit–cost ratio. The May 10 sowing, coupled with efficacious weed control measures, significantly reduced weed density and biomass while concomitantly improving nutrient uptake and economic returns. The results indicate that adopting a May 10 sowing date for direct seeded rice, in conjunction with either four conoweedings or the aforementioned sequential herbicide application, can optimize agronomic productivity and economic profitability under the temperate conditions of Kashmir. The study aided in choosing the best sowing window and efficient weed management strategy for attaining higher productivity and profitability of direct seeded rice in temperate conditions.

Optimizing herbicide types and concentrations: Crucial elements for achieving intensive cultivation of common buckwheat

An appropriate herbicide type and concentration is essential for effective weed management and enhancing crop yield. However, the optimal herbicide type and corresponding application concentration for controlling weeds in common buckwheat on the Loess Plateau region of Northwestern China remain unclear. To address this gap, experiments were conducted to investigate the effects of various herbicides on weed control, dry matter accumulation, and grain yield in common buckwheat, and to analyze the variances in weed control efficacy and grain yields of the optimal herbicides at different concentrations. The results showed that both metolachlor and quizalofop-P-ethyl demonstrated effective weed control with lower phytotoxicity. Dry matter accumulation was lower under metolachlor, with no significant differences observed among the post-emergence herbicide treatments. Importantly, metolachlor and quizalofop-P-ethyl promoted the allocation of dry matter to grains. Remarkably, metolachlor and quizalofop-P-ethyl increased the grain yield by 15.59% and 26.97%, respectively, compared to spraying an equivalent amount of water. Additionally, the m2.25, q0.9, and q1.2 treatments exhibited excellent weed control effectiveness. And the higher grainnumber per plant observed under m2.25, q0.9, and q1.2 contributed to the increase in grain yield. Consequently, m2.25, q0.9 and q1.2 increased the grain yield by 34.42%, 38.86% and 33.16%, respectively. These findings demonstrate that applying metolachlor and quizalofop-P-ethyl at 2.25 L ha−1 and 0.9 or 1.2 L ha−1 respectively, is beneficial for efficient weed management and yield enhancement in common buckwheat cultivation on the Loess Plateau region of Northwestern China. These studies provide important guidance for promoting common buckwheat cultivation in this region.

Cotton Cultivation Practices in South-Western Part of Punjab

The study was conducted for three consecutive years (2018/19-2020/21) to investigate the adoption status of cotton crop production practices in Sri Muktsar Sahib district in south-western Punjab. Data pooled for three years showed that the majority of farmers (67.8%) ensured crop sowing at the recommended time, while 32.8 per cent delayed cotton sowing due to the non-availability of canal water for timely pre-sowing irrigation. Concerning nutrition management, 18.5, 45.5 and 33.5 per cent of farmers applied recommended doses of N, P, and K fertilizers, respectively, and 89.5 per cent of farmers applied two or more sprays of potassium nitrate (KNO3). For the management of insect pests, during 2018-19, ~52.9 per cent of farmers had to apply 5-6 sprays, while during the next two years, ~55.4 and 81.5 per cent of farmers applied 3-4 insecticide sprays. The average seed cotton yield during 1st year of study (2018-19) was 15.6 q ha-1 which was increased to 22.6 q ha-1 during 2019-20 and 23.1 q ha-1 during 2020-21. This study reiterates that there is a need to update the farmers regarding knowledge of improved cotton cultivation techniques for efficient weed, nutrition, water, and insect-pest management in cotton cultivation in Punjab.

Management of Herbicide resistant Phalaris minor: A Review

Littleseed canarygrass (Phalaris minor Retz), an annual species of the family Poaceae, is a major weed problem in many wheat-producing countries. The excessive dependence on herbicides for its control led to the evolution of multiple herbicides resistance and yield losses. The first case of resistant P. minor in India was to the Photosystem-II inhibitor isoproturon in the early 1990’s. P. minor has been found resistant to Acetolactate Synthase (ALS) inhibitors, Acetyl-CoA Carboxylase (ACCase) inhibitors, Photosystem II inhibitors. It is highly competitive and in severe cases can cause complete crop failure, forcing farmers to harvest their crop as fodder or ploughing the standing crop along with weeds. For management of these multiple herbicide resistant P. minor, pyroxasulfone, pendimethalin, flumioxazin, trifluralin and flufenacet can be used as alternative herbicides. Moreover, in-depth biological and ecological studies on P. minor should be carried out for devising integrated weed management strategies. The long-term strategies of efficient weed management and sustainability of wheat production should include the use of alternative herbicides, herbicide mixture, crop rotation along with other non-chemical methods like manual removal of weeds, mulching, Summer ploughing etc providing the competitive advantages to the wheat crop over P. minor, at the same time increasing the profitability of the farmer by controlling the weed effectively and reducing the selection pressure on the weeds which will inturn reduce the resistance development in weeds

Integrated Weed Management in Minor Millets: A Review

Presently, agriculture is facing tremendous problem due to climate change and global warming. To ensure food and nutritional security at national level, there is an immediate need to promote the cultivation of millets as millets are considered climate smart and nature friendly crops because of high nutritive value and can withstand under warm and drought conditions with short life, low external inputs requirement, tolerance to water and temperatures stress. Ten millet crops have been declared as ‘Nutri Cereals’ which include three major millets i.e., pearl millet, sorghum and finger millet; five minor millets i.e. foxtail millet, proso millet, kodo millet, barnyard millet, little millet; and two pseudo millets i.e. kuttu (buckwheat) and amaranthus. Due to sluggish growth in initial phases of life, millets proved relatively poor competitors against weeds. Manual weeding is the most commonly adopted for weed control in millets. But the non-availability of labour and ever-increasing labour wages have compelled the farmers to seek alternate method of weed management. Herbicide use is the most viable method of weed control but their continuous and excessive use is not advisable due to its ill effects on environment and development of herbicide resistance in weeds. Very limited options are available in literature for weed control in minor millets. Thus, integrated weed management practices should be followed on site and time specific basis for effective and efficient weed management in minor millets. For integrated weed management in minor millets, 2-3 times inter-cultivation and 1-2 time hand weeding during initial 25 days after sowing in addition to pre-emergence spray with Isoproturon @ 0.5 -1.0 kg a.i./ha and post emergence spray of 2, 4-D sodium salt @ 0.75-1.0 kg a.i./ha at 20-25 days after sowing should be done for effective weed control.

Object-level benchmark for deep learning-based detection and classification of weed species

Weeds can decrease yields and the quality of crops. Detection, localisation, and classification of weeds in crops are crucial for developing efficient weed control and management systems. Deep learning (DL) based object detection techniques have been applied in various applications. However, such techniques generally need appropriate datasets. Most available weed datasets only offer image-level annotation, i.e., each image is labelled with one weed species. However, in practice, one image can have multiple weed (and crop) species and/or multiple instances of one species. Consequently, the lack of instance-level annotations of the weed datasets puts a constraint on the applicability of powerful DL techniques. In the current research, we construct an instance-level labelled weed dataset. The images are sourced from a publicly available weed dataset, namely the Corn weed dataset. It has 5997 images of Corn plants and four types of weeds. We annotated the dataset using a bounding box around each instance and labelled them with the appropriate species of the crop or weed. Overall, the images contain about three bounding box annotations on average, while some images have over fifty bounding boxes. To establish the benchmark dataset, we evaluated the dataset using several DL models, including YOLOv7, YOLOv8 and Faster-RCNN, to locate and classify weeds in crops. The performance of the models was compared based on inference time and detection accuracy. YOLOv7 and its variant YOLOv7-tiny models both achieved the highest mean average precision (mAP) of 88.50% and 88.29% and took 2.7 and 1.43 ms, respectively, to classify crop and weed species in an image. YOLOv8m, a variant of YOLOv8, detected the plants in 2.2 ms with the mAP of 87.75%. Data augmentation to address the class imbalance in the dataset improves the mAP results to 89.93% for YOLOv7 and 89.39% for YOLOv8. The detection accuracy and inference time performed by YOLOv7 and YOLOv8 models in this research indicate that these techniques can be used to develop an automatic field-level weed detection system.

Comparative studies of knapsack, boom, and drone sprayers for weed management in soybean (Glycine max L.)

The study titled, "Comparative Evaluation of Knapsack, Boom, and Drone Sprayers for Weed Management in Soybean (Glycine max L.)" was carried out during the Kharif season 2021-22 at an experimental farm affiliated with the Department of Agronomy, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani. The primary objective was to evaluate the comparative efficacy of various sprayers in controlling weeds in soybeans and their work efficiency. The Randomized Block Design (RBD) included ten treatments of pre-emergence (PE) and post-emergence (POE) herbicides applied by knapsack, boom, and drone sprayers. Pendimethalin 30% EC @ 750 g a.i ha−1 was used for pre-emergence herbicide application, and Imazamox 35% EC + Imazethapyr 35% WG @ 70 g a.i ha−1 were used for post-emergence. These treatments were tested on soybean Monocot and Dicot weed count, weed dry weight, weed index, and weed control efficiency. The sprayers were compared for time, water, labor, herbicide, and overall work efficiency. A knapsack sprayer showed the best results for pre- and post-emergence herbicide application, with the lowest weed count, dry weight, control efficiency, and weed index. Boom and drone sprayers followed in effectiveness. Herbicide application was faster with the drone sprayer than with hand weeding, cultural practices, boom sprayer, and knapsack sprayer. Compared to knapsack and boom sprayers, the drone sprayer used less water and labour. Drone sprayers work most efficiently, followed by boom and knapsack sprayers. This study focuses on the prevalence of herbicides and their impact on non-target ecosystems. It aims to develop mitigation strategies by optimizing spraying efficiency and reducing herbicide usage during pre and post emergence. The dissemination of efficient weed management practices that reduce environmental impacts and increase the efficiency of soybean cultivation is consistent with Sustainable Development Goal 15: life on land.

UAV-based Herbicide Application for Efficient Weed Management in Direct-seeded Rice

Background: Weeds are the key pest, which reduce crop productivity. Direct-seeded rice is very prone to early-stage weed infestation during initial crop development. Cultural and mechanical methods are difficult due to unavailability of labour and poor work efficiency. Hence, use of herbicides is an effective method for timely weed control. However, the efficacy of agrochemicals depends on the efficiency of spraying equipment. Conventional knapsack sprayers are used most often to spray herbicides but they are highly time-consuming, labour intensive and labour drudgery practices. Hence, the current experiment was aimed to study the efficiency of unmanned aerial vehicles (UAVs) on weed management. Methods: A field experiment was conducted at Tamil Nadu Agricultural University, Coimbatore during summer, 2022 to evaluate the efficacy of UAV-based herbicide application in direct-seeded rice. The study comprised of five weed management treatments such as pre emergence application of pretilachlor with safener and pyrazosulfuron through both UAV and knapsack sprayer and unweeded check as control. The experimental plot was laid out in a randomized block design with four replications. Result: The experimental findings showed that the application of pre-emergence pretilachlor significantly reduced the density and dry weight of grasses, sedges and broad leaved weeds in knapsack application. Moreover, it was found on par with UAV application of same herbicide without any phytotoxicity to rice seedlings. From the experiment, the application of pre-emergence pretilachlor through UAV is found to be more effective for timely weed control during early stages in direct-seeded rice, which reduce the labour intensity and drudgery than knapsack application.

Sorption, leaching, and degradation of dicamba in two Brazilian soils: A study into soil layers

Understanding the behavior in soil of soluble and mobile herbicides, such as dicamba, is essential for efficient weed management. Thus, the objective of the research was to understand the sorption, leaching and degradation processes of dicamba along the profile of two Brazilian soils (Oxisol and Ultisol). The Oxisol collected is a very deep soil, the A horizon was collected in a layer of 0.10 m deep, the B horizon 2.0 m and the C horizon ranging from 5.0 to 6.0 m. In contrast, the Ultisol presents a difference between the most superficial horizons, the A horizon was collected at a depth of 0.10 m, the B horizon at around 1.0 m depth and the C horizon at a depth of 2.0–3.0 m. A High-Performance Liquid Chromatography (HPLC) was used to determine the herbicide in the soil solution. The Freundlich sorption coefficient (Kf) values of dicamba ranged from 0.53 to 0.88 mg (1-1/n) L1/n kg−1 in Oxisol and 0.25–0.69 mg (1-1/n) L1/n kg−1 in Ultisol, indicating a low sorption capacity of the herbicide in all profiles. The dicamba mobility index was higher in the Ultisol, ranging from 4.22 to 65.8 compared to the Oxisol, which ranged from 0.46 to 8.10. The degradation half-life time (DT50) of dicamba was short (∼4 days) in the A horizon of both soils compared to the other horizons. Moreover, persistence in the B and C horizons was higher in Oxisol (182 and > 250 days) compared to Ultisol (85.6 and 52.1 days, respectively). The sorption and mobility index of dicamba showed a correlation with soil pH and DT50 values, depending on the organic matter (OM) content. The recommendation of use of dicamba should consider the physical and chemical attributes of the soil as an alternative to reduce the risk of environmental contamination.

Weed Response to ALS-Inhibitor Herbicide (Sulfosulfuron + Metsulfuron Methyl) under Increased Temperature and Carbon Dioxide

Information on the impact of climate change on the growth of weed species and their sensitivity to herbicides could help to establish an efficient weed management strategy. Due to the excessive use of acetolactate synthase (ALS)-inhibitor herbicides, resistance to those herbicides is increasing globally. It is, thus, crucial to find out whether the efficacy of these herbicides will change in the future due to the increase in temperatures and carbon dioxide concentration. Therefore, this work aimed to evaluate the impact of temperature and carbon dioxide (CO2) changes on the growth of Amaranthus retroflexus, Bromus tectorum, Chenopodium album, and Echinochloa crus-galli, including the assessment of sulfosulfuron 75% + metsulfuron methyl 5% efficacy in these weeds. A factorial experiment was performed in a completely randomized design with a factorial arrangement (2 × 2 × 6), including two CO2 concentrations (400 and 700 ppm), two temperature regimes (30/20 °C and 34/24 °C day/night), and six herbicide rates (0, 25, 37.5, 50, 62.5, and 75 g ha−1). As a result, it was seen that temperature and CO2 concentration changes influenced the morphological variables of the weeds. The temperature regime affected the herbicide’s effectiveness on B. tectorum and E. crus-galli. The herbicide’s efficacy on weed species was affected by the interaction of herbicide rates and the temperature regime, except for on E. crus-galli; the highest efficacy was observed at 30/20 °C and at a rate 50% higher (75 g ha−1) than the recommended one (50 g ha−1). Except for E. crus-galli, increasing CO2 concentrations enhanced the herbicide efficacy and ALS enzyme activity inhibition in all the weed species, but had the greatest effect on C3 weeds. We found that temperature and CO2 levels can alter the efficacy of weed control with herbicides, with clear differences between C3 and C4 plants. As a result, increased temperature and CO2 concentration will possibly allow better control of weed species such as B. tectorum, C. album and A. retroflexus at lower doses of the ALS herbicide under investigation.

Influence of Sowing Time and Weed Management Practices on the Performance and Weed Dynamics of Direct Drum Seeded Rice.

Direct drum seeding has emerged as a viable and alternate substitute to the current transplanted rice to address constraints of labor and water scarcity as well as rising cultivation costs. However, heavy weed infestation is the main biological factor leading to immense yield loss, which requires immediate attention. Therefore, adoption of efficient weed management practice is critical for the success and widespread adoption of direct seeded rice. In this regard, an experiment was laid out at the Faculty of Agriculture, Wadura, SKUAST of Kashmir, India, in Kharif seasons of 2018 and 2019 to assess the efficiency of direct seeded rice (DSR) under two sowing dates (D1: 10th May and D2: 3rd June) and six weed management strategies (W1: weedy check (untreated check), W2: four mechanized conoweedings at 15, 30, 45, and 60 DAS (days after sowing), equivalent to weed free (four conoweedings, equivalent to weed free), W3: bensulfuron-methyl + pretilachlor @ 60 and 600 g a.i. ha-1 as pre-emergence (BSM + pretilachlor, PE), W4: oxyfluorfen @ 750 g a.i. ha-1 as pre-emergence (oxyfluorfen, PE), W5: bensulfuron-methyl + pretilachlor @ 60 and 600 g a.i. ha-1 as pre-emergence followed by 2,4-D @ 0.75 kg a.i. ha-1 as post-emergence (30-35 DAS) (BSM + pretilachlor PE fb 2,4-D PoE), and W6: oxyfluorfen @ 750 g a.i. ha-1 as pre-emergence followed by 2,4-D @ 0.75 kg a.i. ha-1 as post-emergence (30-35 DAS) (oxyfluorfen PE fb 2,4-D PoE) on growth characteristics, productivity, weed infestation, and nutrient dynamics. The pooled results showed that 10th May sowing recorded significantly higher values of growth characteristics viz. plant height, dry matter production, tiller count, and yield characteristics, including panicle weight, panicle length, filled grains per panicle, and test weight, as compared to delayed sowing (3rd June). Earlier sowing (10th May) produced significantly higher grain yield (7.33 t ha-1) and straw yield (8.99 t ha-1) when compared to the delayed sowing (3rd June) which produced a grain yield of 6.08 t ha-1 and straw yield of 7.93 t ha-1. Among weed management strategies, four mechanized conoweeding at 15, 30, 45, and 60 DAS resulted in enhanced growth, yield characteristics, and yield but was statistically similar to bensulfuron-methyl (BSM) + pretilachlor PE fb 2,4-D post-emergence (PoE). Delayed sowing (3rd June; D2) recorded significantly higher weed density and dry-weed biomass as compared to earlier sowing (10th May; D1). Among the herbicides tested, sequential application of BSM + pretilachlor PE fb 2,4-D PoE proved an efficient weed management practice with a significantly reduced population and dry weight of weeds. Therefore, it was concluded that 10th May sowing with four mechanized conoweedings or sequential application of BSM + pretilachlor PE fb 2,4-D PoE is promising for improving productivity and efficient weed control in direct drum seeded rice under temperate Kashmir conditions.

Innovation in agriculture and the agri-food chain: Some insights

<abstract> <p>Information on the impact of climate change on the growth of weed species and their sensitivity to herbicides could help to establish an efficient weed management strategy. Due to the excessive use of acetolactate synthase (ALS) inhibitor herbicides, resistance to those herbicides is increasing globally. It is thus crucial to find out whether the efficacy of these herbicides will change in the future due to the increase in carbon dioxide concentration and in the temperatures. This work therefore aims to evaluate the impact of temperature and carbon dioxide (CO<sub>2</sub>) changes on the growth of <italic>Amaranthus retroflexus</italic>, <italic>Bromus tectorum</italic>, <italic>Chenopodium album</italic> and <italic>Echinochloa crus-galli</italic>, including the assessment of herbicide (sulfosulfuron 75% + metsulfuron methyl 5%) (SMM) efficiency in these weeds. A factorial experiment was performed in a completely randomized design with three factors, including two CO<sub>2</sub> concentrations (400 and 700 ppm), two temperature regimes (30/20 ℃ and 34/24 ℃ day/night), and six herbicide rates (0, 25, 37.5, 50, 62.5 and 75 g a.e. ha<sup>−1</sup>) in four replications. As a result, it was seen that temperature and CO<sub>2</sub> concentration changes influenced the morphological parameters of the weeds. The main effect of the temperature regime on the herbicide's effectiveness, except for <italic>B. tectorum</italic>, was not statistically significant. The interaction of herbicide rates and temperature with the herbicide's efficacy was only significant for <italic>E. crus-galli</italic>; the highest efficacy was observed at 30/20 ℃ and at a rate 50% higher (75 g a.e. ha<sup>−1</sup>) than the recommended one (50 g a.e. ha<sup>−1</sup>). Increasing CO<sub>2</sub> concentrations enhanced the herbicide's efficiency and ALS enzyme activity inhibition in all the weed species, but had the greatest effect on C<sub>3</sub> weeds. Our results showed that temperature and CO<sub>2</sub> levels associated with climate change can interact to alter the efficacy of herbicidal weed control and that there are differences between plants with the C<sub>3</sub> and C<sub>4</sub> photosynthesis pathways. As a result, in the future, breeders and farmers could achieve the results desired by applying lower doses of this herbicide.</p> </abstract>

Tropical Field Observation of Weed Permanent Shading on Solar PV Surface

Solar Photovoltaic (PV) largely depends on the sun irradiation or insolation level (in W/m2) on its surface for electricity conversion process. Cloud movement especially thick cloud near to earth surface creates a non-permanent shading on solar PV farms top surface which significantly reduce the electricity yield. Improper weed management in large scale solarfarms would create a permanent shading to the PV surface especially with creeping plants. Thus, this work implies freely available application namely Pl@ntNet and Canopeo to analyse the impacts of weed surface cover in Solarfarms. Images of specified weed growing above the solar PV surface are captured and identified using Pl@ntNet application to determine the type of weed. Weed identification is the first stage of efficient weed management to aid in a fundamental understanding of the life cycle and biology of the weeds for proper control measures. The same images are used in Canopeo application to determine the surface coverage by means of Quadrat sampling. This information will be invaluable to solarfarm operators showing the significant energy reduction when the solar PV surface are covered by weeds.

Efficient weed management in groundnut (Arachis hypogaea) through appropriate herbicides

A field experiment was conducted during 2017–18 and 2018–19 in kharif season at Instructional Farm of Krishi Vigyan Kendra, Chhatarpur to study the suitable herbicides for effective management of weed flora of groundnut crop. Randomized block design was used with 4 replications consisting of 7 treatments as detailed in methodology. The results showed that combination of two compatible herbicide molecules like Imazethapyr 100 g a.i./ha + Quizalofop @37.5 g a.i/ha were quite effective against dominated mixed weed flora in groundnut, resulting in higher WCE, WCI, yield and economic net return (93.63%, 93.57%, 16.2 q/ha and `44655/ha) fb use of Imazethapyr @100 g a.i./ha + Fenoxaprop @37.5 g a.i/ha (90.44%, 90.5% 15.2 q/ha and `39380/ha respectively) as compared to control plot. Therefore, above herbicides will be better alternative for suppressing weed flora in the groundnut crop than the sole herbicide.

Seed Germination Ecology of Chenopodium album and Chenopodium murale.

Chenopodium album L. and Chenopodium murale L. are two principal weed species, causing substantial damage to numerous winter crops across the globe. For sustainable and resource-efficient management strategies, it is important to understand weeds' germination behaviour under diverse conditions. For the germination investigations, seeds of both species were incubated for 15 days under different temperatures (10-30 °C), salinity (0-260 mM NaCl), osmotic stress (0-1 MPa), pH (4-10), and heating magnitudes (50-200 °C). The results indicate that the germination rates of C. album and C. murale were 54-95% and 63-97%, respectively, under a temperature range of 10 to 30 °C. The salinity levels for a 50% reduction in the maximum germination (GR50) for C. album and C. murale were 139.9 and 146.3 mM NaCl, respectively. Regarding osmotic stress levels, the GR50 values for C. album and C. murale were 0.44 and 0.43 MPa, respectively. The two species showed >95% germination with exposure to an initial temperature of 75 °C for 5 min; however, seeds exposed to 100 °C and higher temperatures did not show any germination. Furthermore, a drastic reduction in germination was observed when the pH was less than 6.0 and greater than 8.0. The study generated information on the germination biology of two major weed species under diverse ecological scenarios, which may be useful in developing efficient weed management tactics for similar species in future agri-food systems.

Weed Control Efficiencies, Grain Yield and Economics as Affected by Seedbed Preparation and Weed Management Practices in Central Terai, Nepal

Grain yield under dry direct seeded rice (DDSR) is primarily limited due to weeds. Therefore, a field experiment was conducted at Rampur, Chitwan during the monsoon season, of 2014. The treatments consisted of two methods of seedbed preparation in the main plot and six weed management methods in the sub-plot arranged in split plot design with four replications. Results revealed that the grain yield of dry-direct seeded rice did not vary due to seedbed preparation methods. However, weedy check treatments reduced more than 92.78 % of grain yield of dry-direct seeded rice compared to weed-free check. The herbicidal treatments were found to be superior for the benefit-cost ratio. Pendimethalin fb Bispyribac sodium recorded the highest net returns of NRs 68.73 thousand ha-1 and the benefit-cost ratio of 2.55. Sequential application of Pendimethalin followed by Bispyribac sodium was proved to be the most efficient weed management method for dry-direct seeded rice.

Compatible agri-horti systems and weed management options for Mungbean production

For increasing the production of mungbean, a field experiment was conducted in split plot design, to evaluate the compatible agri-horti system and efficient weed management practice. Keeping three agrihorti systems [guava, custard apple and open field] in the main-plots and six weed management practices [pendimethalin 1000 g a.i./ha (PE), imazethapyr 125 and 200 g a.i./ha (PoE), 1- HW (20 DAS), 2-HW (15 & 30 DAS) and weedy check] in sub-plots. Age of agri-horti plantation was 5-years old. Custard apple agrihorti system and open field recorded highest and lowest infestation of weeds, respectively. However, most of the growth, yield attributes and yield did not vary with agri-horti systems. 2-HW recorded the lowest infestation of weeds vis-Ã -vis maximum growth of mungbean. Application of imazethapyr 200 g a.i./ha recorded the lowest growth of predominant weed species, however, dry matter accumulation, yield attributes and yield of mungbean were comparable with imazethapyr 125 g a.i./ha.