Weed Research Articles

Nickel tolerance in cool‐season grasses

AbstractNickel (Ni) toxicity is becoming more prevalent in plants and soils due to increased use of sewage sludge as fertilizers and wastewater irrigation applications; therefore, research on the tolerance of cool‐season turfgrasses and other grassy species is needed. Annual bluegrass (Poa annua L.) is one of most prevalent annual grassy weeds on fine turf worldwide. This research was conducted to examine Ni tolerance of two creeping bentgrass (Agrostis stolonifera L.) cultivars Seaside II and PennLinks II plus a mixture of annual bluegrass and perennial ryegrass (Lolium perenne L.) grown in pure sand and treated with six different Ni concentration levels supplied as NiSO4·6H2O (control, 200, 400, 800, 1600, and 3200 µg L−1 of Ni). Grasses were assessed based on quality, normalized difference vegetation index (NDVI), relative clipping biomass, relative root biomass, relative total biomass, and plant tissue Ni concentration. All measured parameters decreased, and toxicity symptoms followed by growth reductions were noted for all grasses as Ni concentrations increased. Seaside II and PennLinks II at Ni concentrations of 400 and 800 µg L−1 were noted to be at acceptable turf quality or higher, when weedy species mixture was below the acceptable grass quality level. Seaside II displayed acceptable turf quality even at 1600 µg L−1 of Ni. At 3200 µg L−1 of Ni, PennLinks II and weedy species mixture were necrotic at the conclusion of the 8 weeks of the study compared to Seaside II, which was actively growing with signs of yellowing. Results illustrate genetic differences in Ni tolerance, and Seaside II, a salt‐tolerant creeping bentgrass cultivar, has stronger Ni toxic concentration tolerance than PennLinks II and a mixture of two annual weedy grass species, which are often found in the transition zone. This may explore potentials of more research on micronutrient management of weedy species.

Allelopathic potential of warm‐season turfgrass species as an alternative management strategies for weed control

AbstractAlternative cultural methods, such as the selection of a turfgrass species and cultivars, need to be investigated as a weed control tactic since certain turfgrass species/varieties demonstrate potential for weed suppression. The objective of this experiment was to assess the allelopathic potential of common warm‐season turfgrass species (Eremochloa ophiuroides, Stenotaphrum secundatum, and Zoysia japonica) on common turf weeds (Digitaria sanguinalis, Eleusine indica, and Poa annua). Greenhouse and laboratory experiments were conducted to evaluate the effect of turfgrass competition, leaf extracts, and soil leachates on the germination and growth of weed species. Leaf extracts were more effective in suppressing weed species germination and growth than soil leachates. Zoysiagrass leaf extracts reduced the germination of P. annua by 16% and the coleoptile length of E. indica L. by 47% compared to deionized water control. Turfgrass species’ leaf extract stimulates annual bluegrass's coleoptile growth while inhibiting its radicle growth. Warm‐season turfgrass soil leachates did not suppress the germination and radicle growth of weed species. Eremochloa ophiuroides soil leachates were effective in suppressing D. sanguinalis coleoptile length. In this experiment, limited allelopathic effects of turfgrass species were noted. Poa annua germination and growth were reduced in a densely established turf, indicating that turfgrass species were equally inhibitory when competition was present. These results suggest that maintaining a dense and strong turf sward that can outcompete weeds for light, nutrients, and water is a more successful weed management technique than selecting a turfgrass species based on potential allelopathic effects.

Artemisia herba-alba Essential Oil: Chemical Composition, Phytotoxic Activity and Environmental Safety

Weeds cause a decrease in the quantity and quality of agricultural production and economic damage to producers. The prolonged use of synthetic pesticides causes problems of environmental pollution, the possible alteration of agricultural products and problems for human health. For this reason, the scientific community’s search for products of natural origin, which are biodegradable, safe for human health and can act as valid alternatives to traditional herbicides, is growing. Essential oils can have useful implications in agriculture by acting as effective alternatives to chemical herbicides. In this work, the chemical composition of an EO from Artemisia herba-alba and its herbicidal properties were studied on two weeds (Lolium multiflorum and Trifolium pratense) and two crops (Brassica napus and Hordeum vulgare) and its environmental safety was also assessed using three model organisms: Chaoborus sp., Tubifex tubifex and Eisenia foetida. The principal component of the EO was camphor (26.02%), with α- and β-thujone (9.60 and 8.38%, respectively), 1,8-cineole (8.02%), piperitenone (5.29%) and camphene (4.95%) as the main components. The EO demonstrated variable phytotoxic effects with a dose-dependent manner, inhibiting both the germination and the radical elongation of the tested seeds, and was also found to be environmentally safe for the selected organisms. The results lay the foundation for considering this EO as a potential weed control agent.

Pearl Millet Cover Crop Extract Inhibits the Development of the Weed Ipomoea grandifolia by Inducing Oxidative Stress in Primary Roots and Affecting Photosynthesis Efficiency

The cover crop Pennisetum glaucum (L.) R.Br. (pearl millet) reduces the emergence of weed species in the field through a mechanism that is not fully known. The identification of the allelopathic activity of pearl millet can contribute to the development of no-tillage techniques to produce crops without or with low doses of herbicides. This issue was investigated by testing the effects of extracts from the aerial parts of pearl millet on the germination and growth of the weeds Bidens pilosa L., Euphorbia heterophylla L., and Ipomoea grandifolia (Dammer) O’Donell under laboratory conditions. The ethyl acetate fraction (EAF) at a concentration of 2000 µg mL−1 was inactive on Bidens pilosa; it inhibited root length (−72%) and seedling fresh weight (−41%) of E. heterophylla, and in I. grandifolia the length of primary root and aerial parts and the fresh and dry weight of seedlings were reduced by 63%, 32%, 25%, and 12%, respectively. In roots of I. grandifolia seedlings, at the initial development stage, EAF induced oxidative stress and increased electrolyte leakage. At the juvenile vegetative stage, a lower concentration of EAF (250 µg mL−1) induced a stimulus in seedling growth (+60% in root length and +23% in aerial parts length) that was associated with increased photosynthetic efficiency. However, at higher concentrations (1000 µg mL−1), it induced the opposite effects, inhibiting the growth of root (−41%) and aerial parts (−25%), with reduced superoxide dismutase activity and photosynthetic efficiency. The stilbenoid pallidol was identified as the main compound in EAF. The allelopathic activity of pearl millet may be attributed, at least in part, to the impairment of energy metabolism and the induction of oxidative stress in weed seedlings, with pallidol possibly involved in this action. Such findings demonstrated that the application of the EAF extract from pearl millet can be a natural and renewable alternative tool for weed control.

Could adjuvants serve as an agroecological tool?

Adjuvants are agrochemicals or natural substances, commonly mixed with pesticides to increase their efficacy or reduce off-target movement by modifying the physical properties of the spray solution, such as surface tension, droplet size, and spreadability, which ultimately improve pesticide adhesion and coverage on target surfaces. Adjuvant use across Europe remains less widespread compared to regions like the USA, where adjuvants are often recommended or required with certain herbicide applications. This paper highlights the potential benefits of incorporating adjuvants with herbicides in weed control, particularly as a strategy to reduce overall herbicide use. Findings from dose-response research on available adjuvants suggest they may enable the application of lower herbicide rates than typically recommended, without sacrificing effectiveness, thereby contributing to the goal of reducing herbicide use by 50% by 2030 in Europe. Furthermore, literature findings indicate that adjuvants significantly improve weed control by enhancing the performance of active ingredients, with efficacy increases of up to 50% compared to using herbicides alone. The integration of adjuvants into herbicide tank mixtures offers considerable promise, especially for managing herbicide-resistant weeds and achieving effective weed control.

Allelopathic potential of cool‐season turfgrass species as an alternative management strategy for weed control

AbstractHerbicides are a common input in turfgrass systems. Selecting turfgrass species that have either the ability to out‐compete weeds or inhibit their germination and establishment is a primary integrated weed management strategy to reduce herbicide use. The objective of this experiment was to assess the allelopathic potential of common cool‐season turfgrass species (Festuca arundinacea, Festuca brevipila, Festuca rubra ssp. rubra, Festuca rubra ssp. littoralis, Festuca rubra ssp. commutata, Lolium perenne, and Poa pratensis) on common turf weeds (Digitaria sanguinalis, Eleusine indica, Poa annua, and Taraxacum officinale). Greenhouse and laboratory experiments were conducted to evaluate the effect of turfgrass competition, leaf extracts, and soil leachates on the germination and growth of weed species. Leaf extracts and soil leachates of turfgrass species generally had more effect on radicle growth than on germination and coleoptile (or hypocotyl) growth. Cool‐season turfgrass leaf extracts did not suppress the gemination of P. annua, D. sanguinalis, or E. indica. P. pratensis leaf extracts were effective in suppressing Taraxacum officinale germination and emergence. Poa annua emergence and development were significantly lower when seeded into dense, established cool‐season turfgrasses. All turfgrass species were equally inhibitory when the turf was dense and competition was present. Limited allelopathic effects were noted in this experiment. Rather than picking a turfgrass species for potential allelopathic effects, these results point to the more effective weed management strategy of maintaining a dense and robust turf sward capable of outcompeting weeds for light, nutrients, and water.

Optimizing Pyroxasulfone-Coated Fertilizer in Cotton

Abstract Two studies were conducted in 2022 and 2023 near Rocky Mount and Clayton, NC, to determine the optimal granular ammonium sulfate (AMS) rate and application timing for pyroxasulfone-coated AMS. In the rate study, AMS rates included 161, 214, 267, 321, 374, 428, and 481 kg ha-1, equivalent to 34, 45, 56, 67, 79, 90, and 101 kg N ha-1, respectively. All rates were coated with pyroxasulfone at 118 g ai ha-1 and top-dressed onto 5- to 7-leaf cotton. In the timing study, pyroxasulfone (118 g ai ha-1) was coated on AMS and top-dressed at 321 kg ha-1 (67 kg N ha-1) onto 5- to 7-leaf, 9- to 11-leaf, and first bloom cotton. In both studies, weed control and cotton tolerance to pyroxasulfone-coated AMS was compared to pyroxasulfone applied postemergence (POST) and postemergence-directed (POST-directed). The check in both studies received non-herbicide-treated AMS (321 kg ha-1). Before treatment applications, all plots (including the check) were maintained weed-free with glyphosate and glufosinate. In both studies, pyroxasulfone applied POST was most injurious (8 to 16%), while pyroxasulfone-coated AMS resulted in ≤ 4% injury. Additionally, no differences in cotton lint yield were observed in both studies. With the exception of the lowest rate of AMS (161 kg ha-1; 79%), all AMS rates coated with pyroxasulfone controlled Palmer amaranth ≥ 83%, comparable to pyroxasulfone applied POST (92%) and POST-directed (89%). In the timing study, the application method did not affect Palmer amaranth control; however, applications made at the mid- and late timings outperformed early applications. These results indicate pyroxasulfone-coated AMS can control Palmer amaranth comparable to pyroxasulfone applied POST and POST-directed, with minimal risk of cotton injury. However, the application timing could warrant additional treatment to achieve adequate late-season weed control.

Critical Period for Italian ryegrass (Lolium perenne L. spp. multiflorum) Control in Winter Wheat in North Carolina

Field studies were conducted in North Carolina to determine the critical period of weed control (CPWC) for Italian ryegrass in winter wheat. Soft red winter wheat was planted in late fall in 2017 and 2018 in no-till fields near Salisbury, NC. Treatments consisted of allowing weeds to grow from crop emergence for different intervals until removal (“weedy”), maintaining “weed-free” conditions from crop emergence for the same intervals, and then letting the weeds emerge and compete with the crop for the duration of the season. In 2017, weed removal occurred in two-week intervals from crop emergence up to 18 weeks after crop emergence (WAE) and three-week intervals up to 18 WAE in 2018. Additional biological measurements, including Italian ryegrass density and height, were collected at 6, 12, and 18 WAE to characterize the effect of crop-weed interactions on the CPWC and weed populations. Non-linear regression analysis was conducted to relate the timing of weed removal and yield loss. The analysis was done using growing degree days (GDD) accumulated at corresponding WAE. Italian ryegrass density ranged from 292 to 824 plants m-2, which created intense competitive conditions with wheat. In the absence of weed control, yield loss surpassed 60%. Using 5% yield loss as an accepted threshold, the CPWC for Italian ryegrass in no-till planted wheat was estimated to be from 1100 to 1900 GDD. This relatively short period makes it possible to reduce weed control intensity if control actions are properly timed.

Weed Management in Early Planted Soybean Early Planted Soybean Weed Management as Effected by Herbicide Application Rate and Timing

Abstract The opportunity to increase soybean yield has prompted Illinois farmers to plant soybean earlier than historical norms. Extending the growing season with an earlier planting date might alter the relationship between soybean growth and weed emergence timings, potentially altering the optimal herbicide application timings to minimize crop yield loss due to weed interference and ensure minimal weed seed production. The objective of this research was to examine various herbicide treatments applied at different timings and rates to assess the effect on weed control and yield in early planted soybean. Field experiments were conducted in 2021 at three locations across central Illinois to determine effective chemical strategies for weed management in early planted soybean. Preemergence (PRE) treatments consisted of a S-metolachlor plus metribuzin premix applied at planting or just prior to soybean emergence at 1/2x (883 + 210 g ai ha-1) or 1x (1,766 + 420 g ai ha-1) label recommended rates. Postemergence (POST) treatments were applied when weeds reached 10 cm tall and consisted of 1x rates of glufosinate (655 g ai ha-1) plus glyphosate (1,260 g ae ha-1) plus ammonium sulfate, with or without pyroxasulfone at a 1/2x (63 g ai ha-1) or 1x (126 g ai ha-1) rate. Treatments comprised of both a full rate of PRE followed by (fb) a POST resulted in the greatest and most consistent weed control at the final evaluation timing. The addition of pyroxasulfone to POST treatments did not consistently reduce late-season weed emergence. The lack of a consistent effect by pyroxasulfone could be attributed to suppression of weeds by soybean canopy closure due to earlier soybean development. The full rate of PRE extended the timing of POST application 2 to 3 weeks for all treatments at all locations except Urbana. Full-rate PRE treatments also reduced the time between the POST application and soybean canopy closure. Overall, a full rate PRE reduced early season weed interference and minimized soybean yield loss due to weed interference.

Grass Weed Control and Rice Response with Tetflupyrolimet-containing Programs

ABSTRACT Tetflupyrolimet is the first herbicide with a novel site of action labeled preemergence (PRE) and early postemergence for use in agronomic crops in the last three decades. Direct-seeded paddy rice field experiments were conducted near Stuttgart on a silt loam soil, AR, and Keiser on a clay soil, AR, to evaluate tetflupyrolimet-containing herbicide programs in comparison to commercial standards in conventional, imidazolinone-, and quizalofop-resistant rice systems. Additionally, a furrow-irrigated rice experiment was conducted near Colt, AR, on a silt loam soil, and Keiser to ensure clomazone and tetflupyrolimet mixtures compared to commercial standards. Twelve commonly planted rice cultivars were also evaluated in response to a single PRE or postemergence (POST) (2- to 3-leaf rice) application of tetflupyrolimet at 200 and 400 g ai ha-1 in a paddy rice system, near Colt. When averaged over soil texture and site-year, all herbicide programs, provided ≥98% barnyardgrass control at 56 d after (DA) the last application. Visible rice injury varied for each rice system. Still, injury rarely differed amongst herbicide programs, except at a single evaluation timing in the conventional (7 DA 3- to 4-leaf applications) and quizalofop-resistant (preflood) systems. All 12 rice cultivars displayed a high tolerance level to a single PRE or POST application of tetflupyrolimet at 200 and 400 g ai ha-1. No visible injury, stand loss, or negative impact on rice maturity or reduced grain yield was observed for any cultivar. Tetflupyrolimet will be an effective alternative SOA in a program approach for barnyardgrass while maintaining excellent rice crop safety.

Herbicide and irrigation management options in conventionally-tilled wheat: deciphering water and energy budgeting, and grain and monetary output in north-Indian plains

In South Asia, declining water tables due to increased irrigation and labor shortages for manual weeding pose significant challenges for wheat production. Additionally, herbicide resistance, often resulting from poor management practices, further complicates weed problems. The objective of this study was to assess the impacts of traditional irrigation regimens (IRs) and herbicide application on wheat crops. The findings showed that when irrigation was applied at 100 mm CPE (IR4), and at 40 mm CPE (IR1), different combinations of herbicide to weed managment were tested. In comparison to the other treatments, application of irrigation at 40 mm cumulative pan evaporation (IR1) along with the Pendimethalin1000 g ha−1 (pre-em) in combination with clodinafop-propargyl 10% + metribuzin 22% + sulfosulfuron 4.2% at a rate of 1125 g ha−1 at 30 DAS (WM1) produced the best results in terms of crop yields, economic returns, relative water content, consumptive use, rate of water use, water use efficiency, water productivity, energy input–output, energy returns, energy productivity, energy intensity, specific energy, energy efficiency, maximum field capacity, available soil water, and soil profile moisture extraction pattern. The only exceptions were Pendimethalin1000g ha−1 (pre-em) combined with carfentrazone ethyl 20% + sulfosulfuron 25%WG), at the rate of 100 g ha−1 at 30 DAS (WM2) and the weed-free treatment (WM5), where the differences were not statistically significant. The yield of wheat grain (14.26 kg ha−1) and straw (14.41 kg ha−1) decreased as the unit dry matter production of weeds increased. The study recommends exploring additional weed control strategies and irrigation management options in future improve wheat yields in conventionally-tilled systems.

Wheat cultivar mixtures enhance the delivery of agroecosystem services compared to monocultures under contrasted tillage intensities and fertilization

AbstractWheat cultivar mixtures provide a more complex and functional cropping system than monocultures. Their functionality may result in the delivery of agroecosystem services. However, research on cultivar mixture performance has mainly been done in controlled environments. Greenhouses and laboratory experiments do not account for environmental or agronomic factors that may influence the polyculture’s functionality. To fill this research gap, we set up a novel strip-split-block experimental design with three factors (wheat treatment, tillage, and fertilization) in a field long-term trial. We assessed the performance of the modern wheat cultivar Florence-Aurora and the traditional cultivars Xeixa (Triticum aestivum L. subsp. aestivum) and Forment (Triticum turgidum L. subsp. durum) monocultures and their mixture in providing aphid and weed control and promoting crop yield under contrasting tillage practices (moldboard ploughing vs. chisel ploughing) and fertilization (farmyard manure applied or not applied). We analyzed aphid abundance, number of aphids per tiller, parasitism rate, weed abundance and richness, and crop yield. Additionally, we examined wheat establishment, cover, phenology, and height for cultivar characterization. We observed that soil management practices affected some aspects of the cropping system. The wheat cultivars differed in their aphid susceptibility and weed suppression ability, with Florence-Aurora being less suppressant to weeds and more prone to aphid infestation. Most remarkably, our study shows for the first time that mixing wheat cultivars with distinguished traits enhances associational resistance for aphid and weed control. These benefits were specifically important under high weed infestations generated by reduced tillage. Moreover, the yield of Florence-Aurora monoculture and the mixture was found to be influenced by tillage and fertilization. Our study underscores how soil management practices impact the functionality of cultivar mixtures. This emphasizes the need for further field research to better understand the complexity of farming conditions that influence the delivery of agroecosystem services by cultivar mixtures.

Nanobased Natural Polymers as a Carrier System for Glyphosate: An Interesting Approach Aimed at Sustainable Agriculture.

Polymer-based herbicide nanocarriers have shown potential for increasing the herbicide efficacy and environmental safety. This study aimed to develop, characterize, and evaluate toxicity to target and nontarget organisms of natural-based polymeric nanosystems for glyphosate. Polymers such as chitosan (CS), zein (ZN), and lignin (LG) were used in the synthesis. Nanosystem size, surface charge, polydispersity index, encapsulation efficiency, toxicity to weed species (Amaranthus hybridus, Ipomoea grandifolia, and Eleusine indica), and Roundup Ready (RR) crops, soil respiration, and enzyme activity were evaluated. The most stable system was the combination of ZN with the cross-linker poloxamer (PL), with higher weed control efficacy (90-96%) for A. hybridus, compared to commercial glyphosate (40%). No improvement was observed for I. grandifolia and E. indica. No glyphosate toxicity was observed in RR crops, soil respiration, or soil enzymes, indicating no toxic effects of the nanoformulation in these models. ZN-PL systems can be a promising alternative for glyphosate delivery, using environmentally friendly materials, with improved efficiency for weed control in agriculture.

Assessing the combined effects of mechanical and chemical weeding on weed dynamics in winter wheat

AbstractMechanical weeding, such as harrowing, offers a promising approach for reaching the European Union's goal of a 50% reduction in pesticide use. To assess its potential, used alone or with foliar‐applied herbicides without residual activity, a 6‐year study was conducted on winter wheat cultivated in loamy soil under temperate conditions (Belgium). Weed density dynamics and percentage weed control (WC) were measured and compared between wheat tillering (BBCH 27‐29) and wheat canopy closure (BBCH 39‐75). Weeds were categorised as weeds maturing generally synchronously with wheat (OW), newly emergent (NE) weeds, or new weed species (NS) appearing in spring. The presence of OW was negatively correlated with yields (up to −0.44), while spring weeds had low or no impact on yield. Overall, one harrow pass reduced OW pressure significantly, with no statistical differences between one versus two passes (the second pass was performed several days after the first). The percentage of WC reached 92%–94% when herbicide was used in combination with harrowing (respectively for one and two harrow passes), and proved to be more effective than harrowing alone whose efficacy reached 64%–70% (respectively for two and one harrow passes). This study also found evidence effects of natural competition from wheat on weeds. Specifically, 54% WC was observed just after harrowing, and 70% was observed when the wheat canopy was closed. These findings suggest that an integrated weed management approach may involve an initial harrowing pass with subsequent evaluation of its effectiveness prior to commencing another intervention. In the event of poor efficacy, a full dose application of herbicide may be warranted.

Seleção de herbicidas pré-emergentes para o trigo

ABSTRACT Weed control is a challenge in crop management due to the limited number of registered herbicides, especially for preemergent application. This study aimed to investigate the selectivity of pre-emergent herbicides with different mechanisms of action for wheat. The experiment consisted of two stages: the first involved screening under greenhouse conditions, and the second assessing the selected treatments under field conditions, with a focus on crop yield. Plant phytointoxication, crop stand, and shoot dry weight were assessed in the greenhouse experiment, and tillering, crop stand, plant height, canopy closure, yield, 1000-grain weight, and hectoliter weight in the field. Under greenhouse conditions, [imazapic + imazapyr], pendimethalin, isoxaflutole, florpyrauxifen, and halosulfuron-methyl produced the best results and were selected for the field experiment. Florpyrauxifen was the only herbicide that was selective both in greenhouse and field experiments. Isoxaflutole and trifluralin did not damage wheat in any of the field evaluations. Despite reducing crop performance in some assessments, pendimethalin and flumioxazin provided yield, hectoliter weight, and 1000-grain weight results equivalent to the herbicide-free control. Florpyrauxifen (1.08 g ha-1) was the most promising herbicide. Trifluralin (900 g ha-1), pendimethalin (1750 g ha-1), isoxaflutole (60 g ha-1), and flumioxazin (40 and 60 g ha-1) also produced grain yields equivalent to the control without herbicide.

Seletividade de herbicidas para híbrido de milho convencional

ABSTRACT The cultivation of conventional maize in refuge areas is important for preserving Bt technology and serving specific markets with greater added value to the grains. Therefore, research aimed at chemical weed control must also continue to be directed to conventional maize hybrids. The objective was to evaluate the selectivity of herbicides applied in preand post-emergence of a conventional maize hybrid cultivated in the Cerrado biome of Brazil. Two field experiments were set up, one in summer and the other in second season. The treatments were composed of eleven herbicide treatments, whose doses are presented in g ha-1 of active ingredient: S-metolachlor (1,440), S-metolachlor (1,680), mesotrione + atrazine (115.2 + 2,000), mesotrione + atrazine (192 + 2,000), tembotrione + atrazine (75.6 + 2,000), tembotrione + atrazine (100.8 + 2,000), nicosulfuron + atrazine (16 + 2,000), nicosulfuron + atrazine (24 + 2,000), [mesotrione + atrazine] ([120 + 1,200]), sequential application of [mesotrione + atrazine] ([60 + 600]), atrazine (2,000), plus a weeded control. Regardless of the experiment, all herbicides applied preand post-emergence of maize led to low percentages of phytointoxication. In both experiments, none of the treatments caused reductions in crop stand, confirming the absence of plant mortality due to the application of herbicides. Plant tipping/lodging was seen in summer maize, with no treatment effect. Maize 100grain mass and yield did not change as a result of the application of herbicides in preand post-emergence of the crop. All herbicide treatments evaluated showed selectivity for the conventional maize hybrid.

Allelopathic Influence of Artemisia lancea Essential Oil on Selected Broad and Narrow Weeds

The present study analyzed the chemical composition and phytotoxic activity of Artemisia lancea essential oil (EO). Gas chromatography-mass spectrometry (GC-MS) results showed the presence of 55 compounds, representing 82.36% of the entire EO, with eucalyptol (18.7%) being the most abundant constituent. Phytotoxic bioassay results indicated that the EO (concentration ranging from 0.25-5 mg mL-1) inhibited the growth of Amaranthus retroflexus and Setaria viridis. Root length of A. retroflexus and S. viridis were reduced with the increasing concentration of the EO, especially when the EO was applied at 1-5 mg mL-1. When treated with 1-5 mg mL-1 EO, shoot length of A. retroflexus and S. viridis were also significantly suppressed. The half maximal inhibitory concentration (IC50) values for inhibiting root and shoot growth of A. retroflexus by the EO were 0.284 and 0.246 mg mL-1; for S. viridis, the EO showed IC50 values of 0.44 and 0.262 mg mL-1 for root and shoot inhibition, respectively. The most promising findings were observed when A. lancea EO concentration reached 1 mg mL-1 and higher, which completely inhibited seed germination of A. retroflexus and S. viridis. These findings suggest A. lancea EO has potential as an eco-friendly bioherbicide for agricultural weed control.

Inhibition of the invasive plant Ambrosia trifida by Sigesbeckia glabrescens extracts.

Ambrosia trifida is an invasive weed that destroys the local ecological environment, and causes a reduction in population diversity and grassland decline. The evolution of herbicide resistance has also increased the difficulty of managing A. trifida, so interspecific plant competition based on allelopathy has been used as an effective and sustainable ecological alternative. However, how to control A. trifida through interspecific competition and the underlying mechanisms are unclear. Here, we found that extracts from both the roots and leaves of the medicinal plant Sigesbeckia glabrescens suppressed the growth of A. trifida by reducing the plant height and biomass. The decrease in biomass may be explained by disruption of carbon and nitrogen metabolism. These disruptions are due to a significant decrease in the expression of genes related to nitrate absorption and transport in roots and a significant decrease in the expression of key genes related to photosynthesis and carbon fixation. Consequently, genes involved in sucrose synthesis are downregulated. In addition, increases in H2O2 content and respiratory burst oxidase homologue (RbohD) gene expression suggested that A. trifida underwent oxidative stress caused by reactive oxygen species (ROS) bursts, resulting in apoptosis due to the significant upregulation of key genes associated with apoptotic pathways. Furthermore, we identified three main allelochemicals, coumarin, ferulic acid, and 5-aminolevulinic acid (5-ALA), in S. glabrescens extracts and revealed that the combination of these three compounds could suppress the growth of A. trifida seedlings. The phenotypes and transcriptome profiles of the seedlings treated with these chemicals were the same as those of the seedlings treated with the S. glabrescens extracts. Taken together, the results of this study revealed the mechanism underlying the toxic effects of S. glabrescens on A. trifida, providing a theoretical basis for the use of interspecific plant competition for invasive weed control and further application of S. glabrescens allelochemicals in weed management.

Characterization of Parthenium (Parthenium hysterophorus L.) Compost for Plant Nutrient Contents at Ginir District of Bale Zone, South-Eastern Ethiopia

Parthenium (Parthenium hysterophorus L.) characterization in the southeast of Ethiopia, in the Oromia Region, the compost for Major Plant Nutrient Contents experiment was carried out in the Ginir District of the Bale Zone. As a result, the purpose of this research was to evaluate the quality and nutrient content of compost made from parthenium combined with wheat byproduct and farmyard manure. Before they began to bloom, the parthenium plants were harvested and cut into smaller pieces. As a result, parthenium compost was made using three different methods, including parthenium biomass plus farmyard manure, parthenium biomass plus crop residue, and parthenium biomass plus both farmyard manure and crop residue. Important chemical characteristics like pH, EC, OC, TN, available P, CEC, and exchangeable bases (Ca, Mg, K, and Na) and micronutrients (Fe, Mn, Cu, and Zn) were examined using standard practice laboratory techniques. The compost had high plant nutrients and significantly varied among the three Parthenium compost preparation techniques, according to the results of the final laboratory analysis of the prepared and harvested Parthenium compost. As a result, Parthenium compost provides multiple benefits, including high nutrient content, weed control, and the general environmental friendliness of using organic fertilizers.

Efficacy of Glufosinate Ammonium Herbicide on Weed Control, Impact on Soil Chemical Properties and Heavy Metal Accumulation in Cocoa Plantations.

Prolonged use of commonly used herbicides by cocoa farmers such as paraquat and glyphosate have been observed to have residual effects on the environment. Therefore there is a need to screen herbicides such as Glufosinate ammonium-based herbicides for use by cocoa farmers. The experiment was set up at the cocoa experimental plot of the Cocoa Research Institute of Nigeria Headquarters in Ibadan. The 3 treatments which were arranged in a Randomized Complete Block Design are slashing, 100 mls and 200 mls of Glufosinate ammonium per 16L of water (100 mls/16L and 200 mls/16L). Each experimental unit was 6 m × 6 m comprising nine cocoa stands. The treatments were replicated 3 times. Data on the soil's initial physico-chemical properties and after 3 months of each treatment were recorded. Mineral and heavy metal analysis of the leaves and pods before spraying and 3 months after spraying were recorded. The % weed control of the treatments was also observed. Treatment means were separated using the Least Significant Difference (LSD) at a 0.05% probability level. Results showed that Glufosinate ammonium applied at both rates did not load the soil, cocoa leaves and cocoa beans with heavy metals. 200 mls/16L had 85.00% weed control followed by 100 mls/16L (62.70%) and slashing (51.00%) which both had the same statistical result. Glufosinate ammonium at 100 mls/16L can replace slashing to eliminate drudgery while Glufosinate ammonium at 200 mls/16L can be used for more effective weed control without negative effects on the environment and the crop.