Preemergence Herbicide Application Research Articles

Bio-efficacy of Herbicides on Weed Density, Weed Control Efficiency, Productivity and Groundnut Quality in Coastal Zone of Karnataka under Rice-Groundnut System

A field experiment was conducted at Agricultural Research Station, Kumta, Uttara Kannada district during the rabi-summer season of 2016-17 to investigate the Bio-efficacy of herbicides on weed density, weed control efficiency, productivity and groundnut quality in coastal zone of Karnataka under rice-groundnut system. The experiment followed a RBD with nine treatments out of which six treatments involved the pre-emergence application of herbicides followed by either hand weeding or early post-emergence application, along with control treatments. The results indicated that the pre-emergence application of pendimethalin 30% E.C. (1.5 kg ha-1), followed by one hand weeding at 25 days after sowing (DAS), resulted in significantly reduced total weed density and weed dry matter. This treatment also demonstrated higher weed control efficiency and lower weed index. Moreover, it led to increased pod yield, kernel yield and improved quality of groundnut compared to other treatments.

Enhancing Wheat Yield and Economic Viability in Subtropical Rainfed Agriculture through Combined Herbicide Application

The management of weeds remains a critical aspect of agricultural production, particularly in rainfed subtropical regions where weed pressure can significantly impact crop yield and economic returns. This study aimed to evaluate the effects of combined herbicide applications on both the yield and economic viability of wheat (Triticum aestivum L.) in subtropical rainfed agricultural systems. Field trials were conducted over two consecutive growing seasons, employing a randomized complete block design with four treatments: (1) pre-emergence application of herbicide A, (2) pre-emergence application of herbicide B, (3) combined pre-emergence application of herbicides A and B, and (4) control (no herbicide application). The study assessed various parameters including weed density, wheat yield, and economic returns. Results indicated that the combined pre-emergence application of herbicides A and B significantly reduced weed density compared to individual herbicide applications and the control, consequently enhancing wheat yield. Furthermore, economic analysis revealed that the combined herbicide treatment resulted in the highest economic returns compared to individual herbicide applications and the control, indicating its economic viability in rainfed wheat cultivation in subtropical regions. These findings underscore the importance of integrated weed management strategies, particularly the judicious use of combined herbicide applications, for optimizing wheat yield and economic sustainability in subtropical rainfed agriculture.

Response of Jabuticaba [Plinia cauliflora (Mart) Kausel] seedlings to herbicides

Jabuticaba (Plinia sp.) is one of the most important fruit species in the Brazilian flora; it is appreciated for fresh consumption or products produced from its fruits. The establishing of orchards requires the determination of management methods that favor the development and productivity of this species. The objective of this work was to evaluate the response of jabuticaba seedlings to application of herbicides and determine possible phytotoxicity. The experiment was conducted at the Federal Technological University of Paraná, in Dois Vizinhos, PR, Brazil. A randomized block experimental design with four replications was used, with 5 plants per experimental unit. The treatments consisted of applications of pre-emergence herbicides (Dual Gold® and Spider®) and post-emergence herbicides (2,4-D, Ally®, Enlist®, Primatop®, Fusilade®, Imazetapyr, Flex®, Plenum®, and Volcane®). The applied herbicide rates were equivalent to 50% of their commercial recommendation. A spray volume equivalent to 250 L ha-1 was applied, using water as diluent. The following parameters were evaluated 45 days after applications: stem diameter at 1 cm above ground (cm); plant height (cm); numbers of necrotic, chlorotic, shriveled, and healthy leaves; number and length of shoots (cm); survival rate (%); and chlorophyll contents (a, b, and total). The application of the herbicides Ally®, Enlist®, and Flex® resulted in less harmful effects on jabuticaba seedlings. The lowest survival rates were found in plants in the treatments with the herbicides Dual Gold®, Volcane®, and Primatop®.

Investigation of management practices to optimize cereal rye cover crop-based weed mitigation in Canadian sweet corn production

Abstract Fall-sown cereal rye has gained popularity as a cover crop in vegetable production due to its weed-suppressive capabilities. However, previous research has shown that replacing preemergence and/or postemergence herbicide applications with roller-crimped rye has variable success at controlling weeds and maintaining vegetable cash crop yields. The objective of this research was to determine whether roller-crimped rye can provide season-long weed control and maintain sweet corn yield. Two rye cultivars (early vs. standard maturity) were compared at three seeding rates (150, 300, and 600 seeds m−2) for their effect on weed control and sweet corn yield. The trial was conducted at three locations: Harrow, ON, and St. Jean-sur-Richelieu, QC, from 2019 to 2021; and Agassiz, BC, in 2019 and 2021. Results suggest that although the early-maturing cultivar allowed for earlier roller crimping in some locations, it was inferior at weed control and resulted in lower sweet corn yield than local standard cultivars. The average rye biomass was lower than the current literature recommendations, and the resulting level of weed control was not high enough to prevent sweet corn yield loss in cover crop treatments. Weed control provided by roller-crimped rye peaked between crimping and 8 wk after crimping and was highest in the standard cultivars sown at 300 and 600 seeds m−2. Preliminary testing of supplemental postemergence weed control showed evidence for sweet corn yields comparable to the weed-free no-cover crop check. However, more research is needed. Overall, with the cultivars and seeding rates tested, roller-crimped rye is not a suitable stand-alone weed control option in sweet corn production. Given the benefits of cover crops, further research should evaluate its potential as a component of an integrated weed management program.

Can Soil Compaction Alter Morphophysiological Responses and Soybean Yield under Application of Selective Herbicides?

Compacted soils may be negatively affecting the selectivity of herbicides applied in preemergence in the soybean crop. Therefore, the present work aimed to investigate possible negative effects on the morphophysiological characters of soybean plants, as well as on the agronomic and yield performances of this crop. For this purpose, two trials were carried out, one in a greenhouse and the other under field conditions. In a greenhouse, the study was carried out in a completely randomized design in a 2 × 8 factorial, with five replications, while in the field, the design used was randomized blocks, with the treatments arranged in split-plot (2 × 8), with six repetitions. The first factor/plot corresponded to the physical condition of the soil: compacted or not compacted, while the second factor/subplot was constituted by the application of preemergence herbicides: clomazone, diclosulam, flumioxazin, S-metolachlor, [imazethapyr + flumioxazin], [pyroxasulfone + flumioxazin], and [sulfentrazone + diuron], plus a control without herbicide. In the greenhouse study, there was a significant interaction between soil compaction and herbicides applied in preemergence for the relative index of chlorophyll b and root dry mass. Furthermore, the isolated herbicide factor did not promote significant changes in any of the morphophysiological variables evaluated. Compaction alone had a negative impact on the variables relative index of chlorophyll a and carbon assimilation rate, with reductions in the values of these variables when the soybean was submitted to growth in compacted soil. For the field experiment, there were no significant interactions between the factors for any of the analyzed variables, nor the effect of herbicides alone. The isolated soil compaction factor negatively impacted the plant stand and the thousand-grain mass of soybean, showing reductions in the values of this parameter when the soybean was grown in compacted soil.

A systematic review of chemical weed management in peanut (Arachis hypogaea) in the United States: challenges and opportunities

AbstractHerbicides are the primary tool for controlling weeds in peanut (Arachis hypogaea L.) and are crucial to sustainable peanut production in the United States. The literature on chemical weed management in peanut in the past 53 yr (1970 to 2022) in the United States was systematically reviewed to highlight the strengths and weaknesses of different herbicides and identify current research gaps in chemical weed management. Residual weed control in peanut is achieved mainly with dimethenamid-P, ethalfluralin, pendimethalin, and S-metolachlor. More recently, the use of the protoporphyrinogen oxidase inhibitor flumioxazin and acetolactate synthase inhibitors, such as diclosulam, for residual weed control in peanut has increased considerably. Postemergence broadleaf weed control in peanut is achieved mainly with acifluorfen, bentazon, diclosulam, imazapic, lactofen, paraquat, and 2,4-DB, while the graminicides clethodim and sethoxydim are the major postemergence grass weed control herbicides in peanut. Although several herbicides are available for weed control in peanut, no single herbicide can provide season-long weed control due to limited application timing, lack of extended residual activity, variability in weed control spectrum, and rotational restrictions. Therefore, effective weed management in peanut often requires herbicide mixtures and/or sequential application of preplant-incorporated, preemergence, and/or postemergence herbicides. However, the available literature showed a substantive range in herbicide efficacy due to variations in environmental conditions and flushes of weed germination across years and locations. Despite the relatively high efficacy of herbicides, the selection of herbicide-resistant weeds is another area of increasing concern. Future research should focus on developing new strategies for preventing or delaying the development of resistance and improving herbicide efficacy within the context of climate change and emerging constraints such as water shortages, rising temperatures, and increasing CO2 concentration.

A field study on the combined use of pre-emergence herbicide and Clearfield® technology for ryegrass management in wheat crops

Weed interference in wheat crops are known to cause productivity losses. The objective of this work was to evaluate pre-emergence herbicide application efficiency combined with Clearfield® technology (CL) in ryegrass (Lolium multiflorum) management in wheat crops. A field experiment was conducted from July 2020 to December 2021 using randomized block design in a 2×5 factorial arrangement with four replications. Treatments consisted of combinations of pre-emergence herbicide application - without and with pendimethalin at 1365 g a.i. ha-1 (in 2020 crop season) or without and with pyroxasulfone at 125 g a.i. ha-1 (in 2021 crop season) and post-emergence herbicide application - without application; imazamox at 49, 70, and 91 g a.i. ha-1, or pyroxsulam at 18 g a.i. ha-1. Wheat cultivars used were TBIO Capricho CL® and TBIO Ello CL®. The following characteristics were evaluated: phytotoxicity, ryegrass control, plant height, number of spikes m-2, mean spike weight, 100-grain weight, and grain yield. Treatments phytotoxicity did not exceed 5%, being visible only at 7 DAA, from 14 DAA no injury was observed. The combined application of pre-emergence herbicides pendimethalin or pyroxasulfone with post-emergence herbicides imazamox or pyroxsulam provided superior control of ryegrass than the isolated applications. This management resulted in ryegrass control ranging from 88.8% to 100% in 2020 and from 82.3% to 100% in 2021. In general, grain yield was also higher in treatments with combined pre- and post-emergence applications. The pre-emergence herbicide application in combination with CL technology was effective in managing ryegrass, preventing weed interference, and ensuring the productive potential of wheat crops

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.

Effect of tillage and weed control practices on weed density, cassava growth and yield at Mkuranga district, Tanzania

Poor and improper weeding in cassava production has been reported to cause cassava yield losses ranging from 40% to 90%. A study was carried out in 2019/2020 planting season at Kiimbwanindi village, Mkuranga, Tanzania to identify common weeds available in the selected cassava field and then the effect of different integrated weed control options was studied. Till only and till + Ridge, pre-emergence herbicides (Primagram Gold a.i 290 g/L S-metolachlor + 370 g/L atrazine and Oxfen a.i Oxyfluorfen 24% EC), post emergence herbicides (Force up a.i 480 g/L of Glyphosate-Isopropylamine salt) and back pack weeder with modified tines were tested on Cassava variety Kiroba in a factorial experiment arranged in a randomized complete block design (RCBD) replicated three times. Data on weed species, weed density, cassava height, girth and fresh root yield and soil were collected. By using Thomas methodology, perennial weeds Cyperus rotundus, Reissantia sp, Mucuna pruriens and Commelina benghalensis found to be the mostly and abundantly occurred weed species. The combination of tillage practices and pre-emergence herbicides application increased number of days’ weeds took to reemerge. The integrated weed control options significantly affected cassava fresh root weight and biomass, p = 0.019 and p = 0.026, respectively. The correlation analysis showed a non-significant positive relationship between cassava stem height and cassava fresh root weight (r = 0.389, p > 0.05), and cassava stem girth and cassava fresh root weight (r = 0.055, p > 0.05). The study concluded that, the combination of till + ridges, application of pre-emergence herbicide (S-metolachlor + atrazine) and post emergence herbicides (glyphosate) can effectively control weeds and provided favorable environment for cassava growth and root formation as compared to other treatment options.

Growth and agronomic performance of soybean applied with pre-emergence herbicides

Among the factors that limit the productive potential of soybean crops, stands out lodging, in addition to competition with weeds. Given this, the importance of soybean pre-emergence herbicides for different purposes is highlighted; however, they have to be evaluated for selectivity. This study aimed to evaluate the growth and agronomic performance of soybean applied with pre-emergence herbicides. Experiment 1 was conducted in the 2017-2018 season at two locations, and experiment 2 in the 2016-2017 season at one location. Treatments consisted of the application of pre-emergence herbicides in soybean in a randomized block design with four replications. Crop injury and chlorophyll indices (experiment 1) and variables related to agronomic performance (experiments 1 and 2) were assessed. Diclosulam and chlorimuron showed potential for application at pre-emergence to reduce plant height and consequently plant lodging. Moreover, diclosulam, chlorimuron, sulfentrazone, flumioxazin, s-metolachlor, pendimethalin, trifluralin, imazethapyr/flumioxazin, and oxyfluorfen did not negatively affect agronomic performance when applied at pre-emergence of soybean. This study evidenced the selectivity of pre-emergence herbicides to soybean.

Performance of herbicides for managing weed flora in transplanted aman paddy (Oryza sativa L.)

A field investigation was performed during the rainy seasons of 2018 and 2019 at the Instructional Farm, Bidhan Chandra Krishi Viswavidyalaya, Jaguli, Nadia, West Bengal, India (22056'N and 86048'E, 9.75m above mean sea level) with the aim of determining the comparative effectiveness of different herbicides in controlling various kinds of weeds (grass, sedge and broad-leaf) in the transplanted aman paddy. The experiment was laid out in Randomized Block Design having sixteen treatments with three replication, that includes application of either pre-emergence [butachlor, pretilachlor, pyrazosulfuron ethyl and ready mix (RM) of bensulfuron methyl + pretilachlor at 2 days after transplanting (DAT)] or post-emergence [bispyribac sodium and bispyribac sodium + penoxsulum at 20 DAT] herbicides followed by hand weeding at 40 DAT; application of both pre-emergence and post-emergence herbicides; hand weeding at 20 and 40 DAT and weedy check. Hand weeding at 20 and 40 DAT registered significantly lower weed density, weed dry matter and the highest weed control efficiency. Among the herbicidal treatments, ready-mix formulation of bensulfuron methyl 0.6% + pretilachlor 6% (Londax power 6.6%) performed better in controlling weeds of all categories and recorded higher paddy (3.96 t/ha) and straw yield (4.92 t/ha ) with the maximum weed index which were statistically at par with the hand weeded treatment. Hence, to fetch the effective suppression of weed, application of Londax power 6.6% @ 0.66 kg a.i./ha as pre-emergence (at 2 DAT) with hand weeding at 40 DAT can easily replace additional one hand weeding at 20 DAT.

Drone-based herbicide application for energy saving, higher weed control and economics in direct-seeded rice (Oryza sativa)

A field experiment was conducted at Tamil Nadu Agricultural University, Coimbatore during kharif (rainy) and rabi (winter) seasons of 2022 and 2023 to evaluate the efficiency, energy and economics of drone-based herbicide application in direct-seeded rice (Oryza sativa L.). The study was carried out with application of pre-emergence, early post-emergence and post-emergence herbicides using drone and knapsack sprayer to assess the weed control efficiency. Treatments included pretilachlor followed by (fb) application of post-emergence herbicides, such as bispyribacsodium (Na), fenoxyprop ethyl + carfentrazone ethyl and early post-emergence herbicides, such as bispyribac-Na, fenoxyprop ethyl + carfentrazone ethyl, bispyribac-Na fb post-emergence of fenoxyprop ethyl + carfentrazone ethyl, weed-free check and unweeded check. Application of pretilachlor fb bispyribac-Na using knapsack sprayer reduced weed density from 83 to 87% and weed dry weight from 81 to 83% over unweeded plot. Moreover, it was found on par with drone application of same herbicides in both seasons. Pretilachlor fb bispyribac-Na application through knapsack sprayer and drone produced higher grain yield and it was comparable with weed-free plot. Higher net return, benefit: cost ratio (2.27 and 2.09), energy-use efficiency (10.86 and 9.55 MJ) and energy productivity (0.81 and 0.71 kg/MJ) were noticed with drone application of pretilachlor fb bispyribac-Na in both the seasons. From the experiment, drone application of pretilachlor fb bispyribac-Na is found as an effective strategy to manage weeds in direct-seeded rice and more advantageous in terms of energy-use and profitability.

Trade-off strategy for the usage of thiencarbazone-methyl·isoxaflutole on maize fields: Nitrogen-associated microbial response and environmental implications

Due to the lack of knowledge on the mechanism of the effect of new herbicides on nitrogen-functioning microorganisms and nitrogen use efficiency, a balancing strategy for the application of new herbicides in maize fields is rarely proposed. By studying the effects of thiencarbazone-methyl·isoxaflutole (TMI) on nitrogen transformation in soil and nitrogen agronomic efficiency (NAE) of maize, the mechanism of nitrogen functional groups and genes involved was revealed, and controlling factors affecting soil nitrogen transformation were identified. Results showed that on day 18, the nitrate nitrogen (NO3−-N) content increased but ammonium nitrogen (NH4+-N) content decreased with the TMI application. This can be further verified by the positive correlations (p < 0.05) among isoxaflutole residues, “aerobic_ammonia_oxidation” and NO3−-N content. The NH4+-N content increased significantly with TMI application at 10 times the recommended dose (412.5 ml hm−2) on days 30 and 45, which explains the high value of NAE at the high-dose application of TMI. Random forest model and redundancy analysis confirmed the significant impacts of the nifH gene on NH4+-N content and TMI residues on NO3−-N content (p < 0.05). Comprehensively considering the disturbance of nitrogen-related microorganisms and the effects on the NAE of maize, this research proposed a trade-off strategy for the application of new pre-emergence herbicide in maize fields, involving background investigation, experimental design, analytical methods and trade-off indicators. This may be further popularised and achieve a balance between economic and environmental benefits.

Using soybean chaff lining to manage waterhemp (Amaranthus tuberculatus) in a soybean–corn rotation

AbstractWaterhemp (Amaranthus tuberculatus[Moq.] Sauer) escapes are common in midwestern U.S. soybean [Glycine max(L.) Merr.] fields due to the continued rise in herbicide-resistant (HR) populations. In a conventional harvesting system, weed seeds are harvested with the crop grain and spread back on to the field. Harvest weed seed control methods such as chaff lining concentrate weed seed-bearing crop and weed chaff into a narrow row (chaff line). These chaff lines (30- to 50-cm wide) are undisturbed the following growing seasons, under the assumption that the chaff line creates an environment less favorable for weed seed germination and survival. Field experiments were conducted in a soybean–corn (Zea maysL.) rotation in 2020 and 2021 in Ames, IA, and Roland, IA, to quantify the effectiveness of chaff lining for managingA. tuberculatusseeds. About 70% of theA. tuberculatusseeds were retained on the mother plant at soybean harvest in 2020. The chaff lining system concentrated more than 99% of theA. tuberculatusseeds exiting the combine into the chaff line. AlthoughA. tuberculatuspopulation density in 2021 was 76% higher inside the chaff line than outside the chaff line,A. tuberculatusaboveground biomass was 63% lower inside the chaff line than outside the chaff line at 12 wk after corn planting. Similarly,A. tuberculatusinside the chaff line had delayed emergence compared withA. tuberculatusoutside the chaff line. Application of preemergence herbicides in corn inside the chaff line delayedA. tuberculatusemergence by more than 2 wk compared withA. tuberculatusoutside the chaff line. Additionally, a follow-up postemergence herbicide application in corn was needed only inside the chaff line to manageA. tuberculatus, suggesting the possibility of lower overall herbicide use. These results support implementing chaff lining in soybean-based crop systems of the U.S. Midwest to help manage HRA. tuberculatusseedbanks.

Standardization of Management Strategy for Chickpea (Cicer arietinum L.) under Different Levels of Crop Residue Retention in Conservation Agriculture

A field experiment was conducted at ICAR- Indian Institute of Soil Science (IISS), Bhopal (Madhya Pradesh) to evaluate the impact of different levels of crop residue retention and herbicidal weed control measures on weed dynamics, crop growth and yield characteristics of chickpea crop under conservation agriculture. Data were recorded on weed study, crop growth and yield characters of chickpea. Results indicate that pre-emergence herbicide application treatments (H1 and H2) were found to be effective in reducing weed density at 30 DAS (63.56%) as compared to post emergence treatments which were applied after recording observations on weed density at 30 DAS. It has been observed that post emergence application of imazethapyr @ 25 g a.i. ha-1 was found to restrict crop growth for a period of 10-15 days as compared to pre-emergence treatments. The results on crop growth and yield parameters revealed that higher residue retention level treatment (90% crop residue retention) recorded significantly higher plant height (54.81cm), dry matter plant-1 (18.39 g plant-1), number of pods plant-1 (36.46), seeds plant-1 (47.11), seed yield (1202 kg ha-1) and straw yield (2916 kg ha-1) as compared to no crop residue retention.

Sericea lespedeza control with postemergence and preemergence herbicide applications in fields managed for northern bobwhite

AbstractSericea lespedeza (Lespedeza cuneata) is an invasive nonnative legume that commonly occurs on sites managed for northern bobwhite (Colinus virginianus). Sericea reduces bobwhite habitat availability by outcompeting native plants that provide food and cover. Sericea can be controlled with postemergence herbicides such as glyphosate as well as a mixture of triclopyr with fluroxypyr, but these herbicides do not provide preemergence control. Imazapic has been effective at controlling a limited number of planted sericea seeds, but the efficacy of imazapic at various application rates to control sericea seedbank response following treatment with a postemergence herbicide has not been evaluated. We designed a field experiment to evaluate sericea control and changes in the plant community as related to bobwhite habitat with 2 postemergence herbicides followed by preemergence treatment of imazapic at 3 sites in Tennessee and Alabama, USA, 2018–2022. Specifically, we treated sericea with postemergence broadcast applications of glyphosate or triclopyr with fluroxypyr in 2018 and applied spot treatment with the same herbicides in 2019–2021. We applied imazapic at 4 rates following prescribed fire in 2019 and 2022. We measured coverage of sericea, native forbs, annual grasses, perennial grasses, and bobwhite food plants before treatment in 2018 and after all treatments in 2022. Nearly all postemergence treatments reduced sericea coverage, but imazapic did not increase control compared to postemergence herbicides alone. Perennial grasses used for nesting and bobwhite foraging were maintained following treatments. We recommend managers use either glyphosate or triclopyr with fluroxypyr to control sericea postemergence and consider using a low rate of imazapic to reduce annual grasses if coverage is a problem on the site.

Effect of Different Dose of Herbicide on Soil Physico-chemical and Biological Properties after Harvest of Wheat

The purpose of the present experiment is to evaluate the efficacy of herbicide to control of weeds in wheat crop. The field experiment was conducted at Agricultural Research Farm, Division of Agronomy, BHU, Varanasi, India. In the experimental field weeds were controlled by pre-emergence application of herbicides viz.,pendimethalin 30% EC @ 600 g ha-1,pendimethalin 30% EC @ 900 g ha-1, pendimethalin 30% EC @ 1200 g ha-1, pendimethalin 30% EC @ 1500 g ha-1,metribuzin 70% WP @ 210 g ha-1 weed free (two hands weeding) and Untreated Control (Weedy check). Effect of treatments on soil physico-chemical properties like soil bulk density, soil p=H, electric conductivity and organic carbon are not significance variation among the treatments. The available nitrogen in soil after harvest of wheat was more under hand weeded treated plots which was statistically comparable with application of pendimethalin 30% EC @ 900 g ha-1 over the rest of the treatments. However, available phosphorus and potassium in non-significant it did not influenced by the treatments.

Efficacy of Pendimethalin Rates on Barnyard Grass (Echinochloa crus-galli (L.) Beauv) and Their Effect on Photosynthetic Performance in Rice

Pendimethalin herbicide toxicity to rice plants and barnyard grass invasion have increasingly affected the productivity of direct-seeded rice (DSR) in the fields. Whether and how to promote DSR productivity and sustain weed management depend on the appropriate pre-emergence herbicide application rate to minimise its toxicity in the rice ecosystem. Pot experiments were conducted to determine the effects of pendimethalin rates (1.5, 1.75, 2.0 kg a.i. ha−1, two control treatments include the untreated control and the treated control with 1.5 kg a.i. ha−1 S-metolachlor) on barnyard grass (Echinochloa crus-galli (L.) Beaux) and their potential toxicity risk to photosynthetic performances of rice (Topaz and Sen pidao). All the pendimethalin treatments provided excellent control of barnyard grass. Among the treatments, 1.5, 1.75, 2.0 kg a.i. ha−1 pendimethalin and 1.5 kg a.i. ha−1 S-metolachlor (treated control) decreased leaf area of barnyard grass significantly by 38.9, 49.6, 49.6 and 46.2%, respectively, compared with the untreated control at 40 days after sowing (DAS). The above-ground biomass of barnyard grass significantly decreased by 40% (1.48 g plant−1) with 2.0 kg a.i. ha−1 pendimethalin and by 46.2% (1.33 g plant−1) when 1.5 kg a.i. ha−1S-metolachlor was applied at 40 DAS compared with the untreated pots. Higher pendimethalin rates increased toxicity in Topaz and Sen pidao varieties, and 2.0 kg a.i. ha−1 pendimethalin significantly reduced effective quantum yield (light-adapted) of photosystem (PS) II by 18% (0.58) and 19% (0.52), respectively, compared with the untreated control. Application of 2.0 kg a.i. ha−1 pendimethalin rate significantly decreased the maximum quantum yield (dark-adapted) of Sen pidao (0.66) compared with 1.5 kg a.i. ha−1 pendimethalin (0.68) including the untreated control. All pendimethalin treatments suppressed above-ground biomass at 55 DAS, but above-ground biomass of barnyard grass significantly decreased by 59.9% when 2.0 kg a.i. ha−1 pendimethalin was applied compared with the untreated control. Although application of 1.5 kg a.i. ha−1 pendimethalin rates reduced the effective quantum yield (light-adapted) of photosystem II of Sen pidao (0.55) by a small percentage (8%) than Topaz (0.65), it was non-toxic for both varieties compared with 2.0 kg a.i. ha−1 pendimethalin. Therefore, the use of 1.5 kg a.i. ha−1 pendimethalin can be used for effective weed management in the direct seeding of rice at an early growth stage.

Germination responses of vipergrass (Dinebra retroflexa) to environmental factors and herbicide options for its control

AbstractVipergrass [Dinebra retroflexa (Vahl) Panzer] is an annual weed of the Poaceae family distributed in several parts of Australia, Asia, and Europe. Very limited information is available on its germination response to different environmental conditions. Knowledge of its seed ecology and biology could help in formulating better weed management decisions. Experiments were conducted to study the effect of alternating temperatures, light conditions, salt stress, water stress, seed burial depths, and wheat residue amounts on the germination or emergence of D. retroflexa. Also, different pre- and postemergence herbicides were evaluated to control D. retroflexa. The highest germination (98%) was recorded at 30/20 C followed by 35/25 C (95%). Light was required for the germination of D. retroflexa. Germination decreased with an increase in sodium chloride (NaCl) concentrations. Even at 80 mM NaCl, 81% of seeds germinated, indicating D. retroflexa’s high salt tolerance. Seed germination gradually decreased with an increase in water stress, and no germination was recorded at −0.8 MPa osmotic potential. The emergence of D. retroflexa decreased with an increase in seed burial depths. The highest germination (83%) was recorded for surface-sown seeds, and emergence was reduced to 0 at a burial depth of 2 cm. Seedling emergence decreased from 82% to 2% when the crop residue load was increased from 0 to 800 kg ha−1. Applications of preemergence herbicides (at field rates), such as diuron, isoxaflutole, pendimethalin, pyroxasulfone, S-metolachlor, terbuthylazine, and triallate, and postemergence herbicides, such as clethodim, haloxyfop-methyl, glufosinate, glyphosate, imazamox plus imazapyr (a commercial mixture), and paraquat, resulted in complete control (100%) of D. retroflexa. Knowledge gained from this study will help us to understand the potential spread of D. retroflexa to other areas and to formulate integrated weed management strategies for its effective control.

Influence of soil herbicides on biometric indicators and yield of sunflower

The article has presented the results of field experiments and laboratory studies of the effectiveness of the use of soil herbicides of various chemical classes in sunflower agrophytocenosis. The effectiveness of the influence of the specified technological aspects on the processes of growth and development, as well as on the formation of quantitative and qualitative indicators of the sunflower harvest, has been established. The research results have confirmed more optimal conditions for the formation of vegetation mass, assimilation apparatus and the root system of sunflower against the background of the application of pre-emergence herbicides. For example, the height of the plants was greater by 2.9–4.5 cm, the length of the root system exceeded the benchmark by 6.1–10.0 cm, the area of the leaf surface — by 1.4–2.8 dm2. When determining such a fundamentally economic and valuable indicator, as seed roughness, а clear regularity of the effect of the use of soil herbicides on this indicator has not been found. The study of the influence of Harness, Dual Gold and Gezagard on the quality indicators of sunflower seeds has showed that the use of herbicides had had a positive effect on the process of oil accumulation. In addition to quality indicators, sunflower yield has been also determined. The yield of the sunflower hybrid Sonachny was 2.64 t/ha when using the herbicide Gezagard, while the yield in the control was 2.13 t/ha. Under the action of Harness and Dual Gold herbicides, the yield was at the level of 2.46–2.47 t/ha, which is 15.5% higher than the control.