Winter Weeds Research Articles

Weed Species’ Diversity and Composition as Shaped by the Interaction of Management, Site, and Soil Variables in Olive Groves of Southern Greece

Gaining a comprehensive understanding of how weed communities respond to both environmental and human-induced factors is of paramount importance in developing effective and ecologically sound weed control strategies. The objectives of the current research were to (1) assess the effect of the main weed management practices used in Greek olive groves on weed species’ diversity; (2) explore the filtering effect of management, site, and soil variables in determining weed species’ composition; and (3) shed light on the association between weed species’ composition and the diversity of the understory vegetation of olive groves. To accomplish these objectives, winter weed species’ coverage was assessed in 116 olive groves, both conventional and organic, distributed across three provinces in southern Greece. The investigation encompassed 29 explanatory variables, categorized into three groups: soil (22), management practices (6), and site conditions (1). It was confirmed that glyphosate use may lower biodiversity and species richness; however, this trend was not universal. In fact, the negative influence of the presence of Oxalis pes-caprae L. on species richness and diversity far outweighed the effect of spraying glyphosate. Redundancy analysis (RDA) revealed that among the 29 variables used to describe the ecological niche, eight (i.e., Mn, Mg, chemical spraying, mowing, rotary tiller, grazing, irrigation, and elevation) were significant and explained 21.5% of the total variation in weed species’ data. Interestingly, the soil Mn concentration was identified as the most influential one, highlighting the importance of soil micronutrients in determining weed species’ composition. The variation partitioning procedure demonstrated that the effect of the management variables on weed species’ composition accounted for 2.2 times the variance of soil variables and 4.5 times the variance of elevation. The present findings might help to enhance optimal management in olive groves that can sustain the biodiversity of flora and, in turn, provide various ecosystem services to agro-ecosystems.

The Influence of Sugar Beet Cultivation Technologies on the Intensity and Species Biodiversity of Weeds

Sugar beet production is highly affected by weeds. The structure of crop rotation, the use of intercrops and different tillage techniques bring several benefits to sugar beet cultivation and create different living conditions for weeds. The response of weed communities in sugar beet stands has not been studied. The experimental plot is in the cadastral area of Ivanovice na Hané (Czech Republic). During an eight-year monitoring period (2013–2020), 46 weed species were identified. The dominant species was Chenopodium album. There were also summer and winter weeds. A more varied crop rotation increased the intensity of weed infestation, with winter weeds being the most common. On the contrary, a higher proportion of cereals in the crop structure favors the presence of summer weeds. The tillage technology and the inclusion of catch crops did not significantly affect the intensity of weed infestation in sugar beet stands or the spectrum of weed species. Current cropping technologies have driven the evolution of weeds. Due to their short life cycles and relatively simple genomes, weeds can respond very quickly to technological measures and, thus, change their harmfulness.

Bird Feeder Explorers Are Not Attracted by the Seeds of Invasive Weeds in Winter

Bird Feeder Explorers Are Not Attracted by the Seeds of Invasive Weeds in Winter

Tillage and Cover Crop Systems Alter Soil Particle Size Distribution in Raised-Bed-and-Furrow Row-Crop Agroecosystems

Conservation alternatives that include no-tillage (NT) and cover crops (CCs) reduce soil erosion in row-crop agroecosystems. However, little information is available about how these alternatives affect soil textural properties responsible for soil fertility. This study evaluated the soil particle size distribution and volumetric water content after three years of consistent management in a raised bed system. There were four treatment systems in a dryland maize/soybean rotation on a silt loam soil (Oxyaquic Fraglossudalfs) that included: NT + CCs, conventional tillage (CT) + CCs, CT + winter weeds, and CT + bare soil in winter in northwest Mississippi. The NT + CC system retained 62% more coarse sand in the furrow than the other systems (2.1% compared to 1.3%; p = 0.02). Regardless of the location, the NT + CC system (2.5%) retained 39% more fine sand than the CT + CC system (1.8%; p = 0.01), suggesting that coarse and fine sands were being trapped in furrows combining NT + CC systems, minimizing their off-site transport. In furrows, CCs increased soil volumetric water content by 47% compared to other winter covers. In beds, NT + CCs increased bed water contents by 20% compared to CT + CCs (17.1 to 14.3%; p < 0.01). Implementing conservation alternatives may promote the retention of sand fractions in silty loam soils that are important in supporting soil fertility and crop sustainability.

Impact of eco-physiological factors on the weed seed germination and emergence: A review on its role in weed management

Dormancy is a typical feature of many weed seed populations, which makes forecasting the time and magnitude of weed emergence difficult. The mean minimum temperatures required for undergoing germination of different weed seeds varies considerably depending on the place of their origin as well as the season on which the plants grow. For instance, the temperature requirement for the germination of summer weeds was observed to be 40% higher than for the winter weeds. Decreasing the water potential from 0 Mpa (mega pascal) to -1.0 Mpa tends to reduce the germination capacity of many weed seeds with some seeds totally failing to germinate at -1.0 Mpa (Chloris truncate, Retama raetam). The effects of planting depth on seed germination and seedling growth of Aframomum citratum on varied soil types indicated that sowing depth greatly influenced the plant's cumulative germination percentage and early growth. The seeds of Sysimbrium officinale (L.), a summer annual species, displayed greater sensitivity to nitrates and lost dormancy throughout the winter. The germination of Thlaspi arvense was also discovered to be stimulated by nitrate only in the presence of light. Tilling the surface of soil has a positive impact in the weed seed germination, however if the tillage depth increases more than 9cm, it tends to lower down the germination of several weed species. However, weed seeds of Bernard grass are among the exceptions in which they germinate better at a shallow depth (2cm). The nature and the thickness of the mulching component influence the germination of weed seeds. Thicker mulches and mulching materials like pearl millet resulted in a greater suppression of the weed seed germination due to an increased allelopathic effects.

Drought Stress Affects the Reproductive Biology of Avena sterilis ssp. ludoviciana

Avena sterilis ssp. ludoviciana (hereafter, A. ludoviciana) is considered the most difficult-to-control winter weed in the Northern Grains Region (NGR) of Australia. The abundance of this weed has increased after the adoption of the no-tillage conservation agriculture (NTCA) approach, which does not bury seeds deep in the soil profile. In addition, the increasing frequency and intensity of drought stress events during the late winter to early spring period in the NGR may modify this weed’s persistence mechanisms, which may further impact crop production. The present study focused on plant maturity time and seed production, dormancy, and longevity of four NGR A. ludoviciana biotypes in relation to the severity of drought stress over 2 consecutive years. Plants of all four A. ludoviciana biotypes were grown under 100% plant available water capacity (PAWC) until panicle initiation. At panicle initiation, very mild (80% PAWC), mild (60% PAWC), moderate (40% PAWC), and severe (20% PAWC) drought stresses were imposed on plants and continued through to maturity; an additional subset of plants were maintained at 100% PAWC through to maturity (control). Plants exposed to severe drought stress matured 24 days earlier than control plants, and produced 34% fewer filled seeds, with seeds having a 42% lower mass, 70% less dormancy, and shorter predicted longevity of at least 2 years compared to the seeds produced on control plants. All reproductive traits were less affected when the severity of the drought stress was decreased. The increasing frequency of drought stress in combination with the widely adopted practice of NTCA favours seeds of A. ludoviciana to undergo rapid germination in the following autumn/winter NGR planting season. However, effective control of A. ludoviciana remains a challenge in the NGR due to this weed’s genetic variability with respect to its response toward the seasonal variability of the NGR.

Effects of paraquat application at cover crop planting on cover crop biomass and weed suppression

AbstractSuccessful cover crop (CC) establishment in the fall is important to maximize CC production, which is critical for achieving many objectives of CCs. Competition from winter weeds may reduce CC establishment and biomass production. A preplant herbicide, such as paraquat, at the time of CC planting in the fall will reduce winter weed pressure resulting in better establishment and growth. An experiment was conducted between 2019 and 2021 to test this hypothesis by evaluating a no-CC check, cereal rye, hairy vetch, crimson clover, and cereal rye + hairy vetch drilled with and without paraquat applied at planting (mid-October to mid-November) following either a corn or soybean crop. Visible weed suppression ratings were collected in mid-April, and total CC and weed biomass was collected in late April. More CC biomass was accumulated following corn than soybean, regardless of preplant herbicide application, because corn is typically harvested before soybeans. Therefore, CCs should be planted early to accumulate more biomass. Weed suppression varied by weed species from all factors, but in general weed suppression was best from a CC mixture containing cereal rye and paraquat applied at planting. If weed suppression is the main goal of the CC, then a preplant herbicide at CC planting is recommended. However, if CC weed suppression goals can be achieved through biomass accumulation, no preplant herbicide is needed. This information is useful for producers to achieve various CC objectives while managing costs.

Soil Solarization as an Alternative Weed Control Method for Archaeological Sites in the Mediterranean Region

Weed species commonly colonize archaeological sites in the Mediterranean region, which poses many issues for the sites’ function and the state of preservation of the monuments. Soil solarization was investigated as an alternative environmentally friendly weed control strategy following legislative limits on the use of herbicides at archaeological sites in Greece. The aim of the study was to evaluate the effectiveness of solarization applied during: (a) summer (the hottest season, as applied in organic and integrated agriculture) and (b) autumn (a season of low tourist activity in archaeological sites), testing two types of plastic mulching: (a) clear and (b) opaque black, and two types of soil preparation: (a) with tillage (as in the agricultural practice of the method) and (b) without tillage. Visual evaluation of the weed control rate suggested that the application of soil solarization during summer resulted in excellent weed control, 100% the following October to December period and over 90% until February. The application of soil solarization during autumn also provided excellent weed control and treatments with clear plastic and tillage resulted in complete (100%) weed control from October to December, while the following month weed control was over 90%. In late March, dry weight of weed biomass was significantly affected by the solarization treatments and it was significantly reduced by treatments with clear plastic. Thus, soil solarization is a sustainable method that has the potential to be used effectively for weed management in archaeological sites of the Mediterranean region. Even treatments without tillage generated excellent weed control during the winter weed flush period and are recommended to protect unexcavated, fragile artifacts. Also, the results of autumn treatments encourage the application of the method during the season of low tourist activity at archaeological sites.

Ecological importance and sociological characters of fourteen widespread weeds and their contribution to the observed (dis)similarity between weed communities

Widespread weeds are a serious nuisance to farmers in any country whether they are growing agricultural or horticultural crops for the great damage they cause to the economy, human health and environment loss. Thus, it is important to measure their ecological importance, sociological characters, their contribution to the observed (dis)similarity between weed communities associated with agronomic and horticulture crops, as well as performing time series analysis and forecasting for their cumulative records. Hopefully with the aforementioned information available, it will be possible to determine the most detrimental which deserve resistance priority within a successful weed control plan, which is the aim of the current study. Depending on species records 2018–2020, fourteen weeds assigned widespread out of the 537-species recorded. Their values in the Importance Value Index (IVI) suggested that Sonchus oleraceus had the highest ecological importance among winter weeds (IVI = 50.5), whereas Bassia indica had the highest IVI among summer weeds (IVI = 42.7) and Cynodon dactylon showed the highest value in the observed competition throughout the year (IVI = 46.2). Analysis of Similarities (ANOSIM) indicates that the weed community structure is significantly affected by widespread weeds and the mean of ranked dissimilarities in floristic composition between groups (weed communities associated with crop categories) is greater than within groups. Similarity Percentage analysis (SIMPER) based on Bray-Curtis as a distance dissimilarity measure, revealed that Cyperus rotundus, Melilotus indicus and Beta vulgaris were the most discriminant species in creating the observed pattern of (dis)similarity between the weed community structure associated with agronomic and horticultural crops during the winter half of the year, while Aster squamatus and Echinochloa colona were the most discriminant during the summer half. It is prominent from the results of the current study and the implemented time-series analysis and forecasting that no-decline is expected in the cumulative records of the 14-widespread weeds when the same current weed management strategy is applied.

Enhanced detoxification via Cyt-P450 governs cross-tolerance to ALS-inhibiting herbicides in weed species of Centaurea

Centaurea is a genus of winter weeds with a similar life cycle and competitive traits, which occurs in small-grains production fields in the central-southern of the Iberian Peninsula. However, most of herbicides recommended for weed management in wheat show poor control of Centaurea species. This study summarizes the biology, herbicide tolerance to acetolactate synthase (ALS) inhibitors, and recommended chemical alternatives for the control of Centaurea species. Four species (C. cyanus L., C. diluta Aiton, C. melitensis L. and C. pullata L. subsp. baetica Talavera), taxonomically characterized, were found as the main important broadleaf weeds in small-grains production fields of the Iberian Peninsula. These species showed innate tolerance to tribenuron-methyl (TM), showing LD50 values (mortality of 50% of a population) higher than the field dose of TM (20 g ai ha−1). The order of tolerance was C. diluta (LD50 = 702 g ha−1) ≫ C. pullata (LD50 = 180 g ha−1) ≫ C. cyanus (LD50 = 65 g ha−1) > C. melitensis (LD50 = 32 g ha−1). Centaurea cyanus and C. melitensis presented higher foliar retention (150–180 μL herbicide solution), absorption (14–28%) and subsequent translocation (7–12%) of TM with respect to the other two species. Centaurea spp. plants were able to metabolize 14C-TM into non-toxic forms (hydroxylated OH-metsulfuron-methyl and conjugated-metsulfuron-methyl), with cytochrome P450 (Cyt-P450) monooxygenases being responsible for herbicide detoxification. Centaurea cyanus and C. mellitensis metabolized up to 25% of TM, while C. diluta and C. pullata metabolized more than 50% of the herbicide. Centaurea species showed 80–100% survival when treated with of florasulam, imazamox and/or metsulfuron-methyl, i.e., these weeds present cross-tolerance to ALS inhibitors. In contrast, auxin mimics herbicides (2,4-D, clopyralid, dicamba, fluroxypir and MCPA) efficiently controlled the four Centaurea species. In addition, the mixture of ALS-inhibitors and auxin mimics also proved to be an interesting alternative for the control of Centaurea. These results show that plants of the genus Centaurea found in the winter cereal fields of the Iberian Peninsula have an innate tolerance to TM and cross-resistance to other ALS-inhibiting herbicides, governed by reduced absorption and translocation, but mainly by the metabolization of the herbicide via Cyt-P450.

Macronutrient Applications and Irrigation Regimes Impact Weed Dynamics and Weed Seedbank Augmentation in Solanum melongena L. Fields

Weeds are a major yield-limiting factor bedeviling eggplant (Solanum melongena L.) production in Russia. This study aimed to determine the influence of macronutrient rates and drip irrigation regimes on weed flora composition and potential soil contamination by weed seedbanks in the eggplant field. Three field experiments were conducted during the 2019–2021 cropping calendar. Two-factorial field experiments were designed in four blocks whereby the composition of weed flora in eggplants was examined under the influence of different macronutrient rates (40 tons manure and N140P30, 40 tons manure and N320P120K210, and control without fertilization), and three thresholds of pre-irrigation soil moisture % least moisture capacity (LMC) (in particular, 70, 80 and 90% LMC). The results demonstrated that nutrient rates contributed to a significant increase in weed density of 27.1 to 37.6%, due to an increase in the number of annual weeds (annual winter weeds and annual early spring weeds), and an increase in soil moisture threshold from 70 to 90%. Nevertheless, low moisture availability between the rows as a result of drip irrigation utilization led to a decrease in weed populations by 10.8 to 15.9%. Potential contamination of the arable soil layer with weed seed was desirably decreased, ranging from 19.8 to 21.7% with the application of fertilizers, compared with the control. Furthermore, the soil weed seedbank was considerably reduced by an increase in the pre-irrigation threshold of soil moisture.

Dose–Response Curves of Pelargonic Acid against Summer and Winter Weeds in Central Italy

Pelargonic acid is a non-selective post-emergence contact bio-herbicide which is registered both for cropping and non-cropping uses in several countries. Dose–response curves on the efficacy of pelargonic acid against common weeds in Mediterranean areas are not available. Dose–response curves of pelargonic acid efficacy against summer and winter annual weeds were evaluated in two field experiments (winter exp. in 2019 and summer exp. in 2020) in central Italy. Pelargonic acid was applied at five doses (1.4, 2.7, 5.4, 10.9 and 21.8 kg a.i. ha−1). Data on weed density, weed dry weight, and weed ground cover were used to calculate the efficacy of pelargonic acid against winter and summer weeds. Data were subjected to a non-linear regression analysis using the logistic dose–response model. Dose of pelargonic acid required to obtain 50%, 70%, 90% and 95% weed control against each weed species (ED50, ED70, ED90 and ED95) were estimated. ED values allowed us to classify winter and summer weeds with respect to their susceptibility to pelargonic acid (ED50 values in kg ha−1 are reported in parenthesis): Kickxia spuria (2.6) (more susceptible) > Heliotropium europaeum (3.0) > Echinochloa crus-galli (3.4) > Solanum nigrum (3.6) > Stachys annua (5.3) > Papaver rhoeas (6.5) > Veronica hederifolia (10.3) > Amaranthus retroflexus (11.4) > Matricaria chamomilla (11.6) > Portulaca oleracea (18.7) > Lolium multiflorum (>21.8) (less susceptible). These findings will allow for the optimization of weed control by pelargonic acid and its use in weed management strategies, both in organic and sustainable cropping systems, under different environmental conditions.

Fall-sown small grain cover crops for weed suppression and soil moisture management in an irrigated organic agroecosystem

Abstract Adoption of cover crops in arid agroecosystems has been slow due to concerns regarding limited water resources and possible soil moisture depletion. In irrigated organic systems, potential ecosystem services from cover crops also must be considered in light of the concerns for water conservation. A constructive balance could be achieved with fall-sown small grain cover crops; however, their impacts on irrigated organic systems are poorly understood. Our first objective was to determine the ability of fall-sown small grains [cereal rye (Secale cereale L), winter wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and oat (Avena sativa L.)] to suppress winter weeds in an irrigated, organic transition field in the southwestern USA. Small grains were planted following the legume sesbania (Sesbania exaltata (Raf.) Rydb. ex A.W. Hill) during Fall 2012 and Fall 2013. In Spring 2013 and 2014, weed densities and biomass were determined within each cover crop treatment and compared against unplanted controls. Results indicated that both barley and oat were effective in suppressing winter weeds. Our second objective was to compare weed suppression and soil moisture levels among seven barley varieties developed in the western United States. Barley varieties (‘Arivat’, ‘Hayes Beardless’, ‘P919’, ‘Robust’, ‘UC603’, ‘UC937’, ‘Washford Beardless’) were fall-sown in replicated strip plots in Fall 2016. Weed densities were measured in Spring 2017 and volumetric soil moisture near the soil surface (5.1 cm depth) was measured at time intervals beginning in December 2016 and ending in March 2017. With the exception of ‘UC937’, barley varieties caused marked reductions in weed density in comparison with the unplanted control. Soil moisture content for the unplanted control was consistently lower than soil moisture contents for barley plots. Barley variety did not influence volumetric soil moisture. During the 2017–2018 growing season, we re-examined three barley varieties considered most amenable to the cropping system requirements (‘Robust’, ‘UC603’, ‘P919’), and these varieties were again found to support few weeds (≤ 5.0 weeds m−2). We conclude that several organically certified barley varieties could fill the need for a ‘non-thirsty’ cover crop that suppresses winter weeds in irrigated organic systems in the southwestern United States.

Effects of Tillage and Winter Cover Management in a Maize Soybean Rotation on Soil Bacterial and Fungal Community Composition

The abundance and distribution of soil microbial populations, i.e., microbial diversity is widely promoted as a key tenant of sustainable agricultural practices and/or soil health. A common approach to describing microbial diversity is phylogenetic analysis with high-throughput sequencing of microbial DNA. However, owing to the tremendous amounts of data generated, a continuing effort is required to better assess the effects of agricultural management systems on soil microbial diversity. Here, we report on the combined effects of management systems on bacterial and fungal diversity in a loessal agricultural soil located in north-central Mississippi, USA. Amplicon sequencing was performed using 16S rRNA-gene and ITS2 from soil samples collected from a three-year study with combinations of maize-soybean crop rotation, tillage practices, and winter vegetative covers. Differences were found in microbial fungal β-diversity among the management systems, with distinct clustering patterns for no-tillage combined with either winter weeds or bare-fallow. Management systems showed a significant influence on soil pH and bulk density, which were positively correlated with fungal community composition. Developments in the description and interpretation of soil microbial diversity will contribute to a more accurate understanding of its role in the various functions and processes important to agricultural soil management.

Herbicide options for sterile oats (Avena ludoviciana) control in winter-planted sorghum

AbstractAustralian grain growers are showing interest in winter-planted sorghum to avoid heat and water stress during the grain-filling stage. Winter-planted sorghum may face competition from winter weeds, including sterile oats, and no herbicides are registered for controlling winter weeds in winter-planted sorghum. The objectives of this study were to (1) identify alternate herbicide options for sterile oats control in winter-sown imidazolinone (IMI)-resistant sorghum and (2) assess the crop injury levels due to herbicides. Sterile oats control with pendimethalin at 0.59 kg ai ha−1, trifluralin at 0.38 kg ai ha−1, and prosulfocarb + S-metolachlor at 2.3 kg ai ha−1 was poor (<30%). Atrazine at 2.7 kg ai ha−1, imazamox + imazapyr at 0.048 kg ai ha−1, and atrazine at 2.7 kg ai ha−1 followed by imazamox + imazapyr at 0.048 kg ai ha−1 reduced the sterile oats biomass by 93%, 96%, and 100% and increased yields by 116%, 136%, and 140%, respectively, compared with nontreated control. Pendimethalin at 0.59 kg ai ha−1 and trifluralin at 0.38 kg ai ha−1 caused phytotoxicity to the crop and gave similar yields to nontreated control. Triallate at 0.8 kg ai ha−1, pyroxasulfone at 0.1 kg ai ha−1, and terbuthylazine at 1.0 kg ai ha−1 provided moderate weed control (44% to 65%) and increased yields by 68%, 108%, and 80%, respectively, compared with nontreated control. This research identified herbicide treatments for the effective control of sterile oats in winter-sown IMI-resistant sorghum that could be used in rotations to reduce the reliance on single herbicide treatments.

Freezing stress induces changes in the morphophysiological of chickpea and wild mustard seedlings

AbstractWild mustard is one of the common and troublesome winter weeds of chickpea fields and a great competitor to reduce the chickpea productivity. Plant species (chickpeas cv. Saral and wild mustard) were compared at freezing temperatures (+4 as a control, 0, −4, −8, −12, −16, and −20°C) based on the morphophysiological traits and their recovery ability. Chickpea chlorophyll fluorescence was more sensitive to low temperatures than wild mustard. Chickpea and wild mustard Fv′/Fm′ (light‐adapted maximum efficiency of photosystem II [PSII] photochemistry) decrease 33% and 11% exposed to −16°C, respectively, compared with +4°C. Particularly at lower temperatures, wild mustard electrolyte leakage was smaller than that of chickpea; the temperature drop had a greater impact on the stems than the leaves. Per temperature degree drop from −12 to −20°C, the survival probability decreased by 12.5%. Wild mustard had a greater root dry matter (RDM) compared with chickpea plants. 50% dry matter depression temperature (RDMT50) could better distinguish among the species freezing response; wild mustard RDMT50 was ~1°C higher than chickpea. Plant survival and Fv′/Fm′ correlation suggested the reliability of chlorophyll fluorescence measurements to assay plants freezing tolerance. The important contribution of a more powerful root system to wild mustard survival under adverse circumstances may be suggested by the positive association between plant survival and RDM. Higher tolerance of wild mustard to freezing stress ultimately leads to greater survival, regeneration, continued growth, and geographical distribution. Therefore, the wild mustard invasion will be possible in chickpea fields after freezing stress, especially in the cold climates and high‐altitude regions.

IDENTIFICATIONS OF PHENOLIC COMPOUNDS AND ALLELOPATHIC EFFECT OF Glycyrrhiza glabra ON GERMINATION AND SEEDLING GROWTH Phalaris minor

The present study was planned to identify the phenolic compounds and allelopathic effect of Glycyrrhiza glabra on germination and seedling growth Phalaris minor at Weed Science Laboratory, Department of Agronomy, University of Agriculture, Faisalabad during winter 2018. The experiments were laid out under a completely randomized design (CRD), having three replicates. In this study seven different concentrations of G. glabra aqueous extracts (0%, 0.25%, 0.5%, 10%, 20%, 40%, and 80%) applied on winter weed P. minor. Data on regarding germination percentage (%), mean Germination time (days), time to 50% germination, root length (mm), shoot length (mm), root fresh weight (mg), shoot fresh weight was recorded following standard procedures. Data were analyzed using Fishers Analysis of Variance. The differences among treatments were separated using a least significant difference test (LSD). Results of experiment revealed that maximum germination percentage (%), Mean Germination time (Days), Time to 50% germination and minimum, root length (mm), shoot length (mm), root fresh weight (mg), shoot fresh weight of p. minor was recorded at 80 % concentration of G. glabra. From the present study, it is concluded that there are phenolic compounds in the wood extract of Glycyrrhiza glabra which cause allelopathic effects on P. minor.

Redox status upon herbicides application in the control of Lolium multiflorum (2n and 4n) as weed

Lolium multiflorum Lam. is a winter weed of difficult control found as diploid (2n) and tetraploid plants (4n). Our study aimed to evaluate the responses of antioxidant enzymes and lipid peroxidation, in both diploid and tetraploid ryegrass varieties. Treatments consisted of control plants (without any herbicide application), and four herbicides with different mechanisms of action. Leaf material was collected 36 h after treatment imposition to determine the lipid peroxidation by ferrous oxidation-xylenol (FOX) content, and the activity of the enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione-S-transferase (GST), and δ-aminolevulinic acid dehydratase (ALAD). Both ryegrass varieties showed oxidative stress mainly due to a downregulated decreased (>31%) in SOD activity and an increase (>32%) in lipid peroxidation (FOX), mainly in ryegrass genotypes exposed to haloxyfop, glyphosate, and iodosulfuron. On the other hand, clethodim-treated plants had an increase in SOD and APX activities, associated with a reduced ALAD activity in both 2n (32%) and 4n (11%) genotypes. In general, the 2n genotype was more affected than the 4n genotype.

Моніторинг забур’яненості посівів сої у короткоротаційній сівозміні

Goal. To monitor the species and quantity composition of weeds in soy sowings of short crop rotation. Methods. Field, laboratory, calculation, and comparison. Results. The research was carried out in 2016–2021 in a stationary 2-factor field experiment on typical chornozem in a short crop rotation (spring barley — sunflower — soy — winter wheat), which includes 3 tillage systems (shelf, shallow disk, and no-till technology), and 3 fertilizer systems (without fertilizers, resource-saving minimized, intensive). The given data indicated that in the agrocenosis of soy, the main type of weediness was mixed, and consisted of small-year monocotyledonous-dicotyledonous, and accompanying rhizomes. It was established that late spring species had the largest share (45–55%). The share of early spring weeds was 18–26%, winter and winter weeds — 7.0–24%, and perennial species — 8–18% of the total amount. The lowest number of weeds in soy crops was fixed for shelf tillage. Conclusions. In the conditions of the zone of unstable moisture of the Left Bank Forest Steppe in short crop rotation with the long-term use of various systems of main tillage on typical shallow low-humus chornozem, for growing soy, it was established that the system of main tillage, which was based on shelf tillage, had significant advantages in terms of reducing weediness of soy sowings over the shelf-less cultivation system with disc tools and no-till technology. It was found that under an intensive fertilizer system, Amaranthus retroflexus L. and Echinochloa crusgalli (L.) Roem. et Schult. develop more intensively. Stellaria media (L.) Vill. and Polygonum scabrum Moench. spread in the background without the use of fertilizers, while under the resource-saving minimized fertilizer system, their number decreases due to the increase in the competitiveness of the culture. The use of shelf cultivation leads to the spread of dicotyledonous weed species in soy agrocenosis. The number of young monocotyledonous and dicotyledonous weed species increases during tillage.

Changing Seasonality of Lolium rigidum (Annual Ryegrass) in Southeastern Australia

Lolium rigidum (annual ryegrass) is the most costly winter weed in Australia and has recently been observed growing in summer. The occurrence of L. rigidum in winter is well documented, but there is no research on populations of this weed that germinate and grow in summer. Herein, we discuss how the potential cause of this seasonal expansion may be related to a change in dormancy duration. Dormancy can affect germination patterns but the growth and reproduction of a plant species depend on other factors, such as temperature and photoperiod. Therefore, dormancy alone cannot be the sole variable responsible for the presence of L. rigidum in summer crops, as typical summer temperature conditions are not favorable for the growth of this weed. Additional changes to the growth and development of summer populations may allow for the adaptation and infestation of L. rigidum in summer conditions.