Abundant Weed Research Articles

A Phytosociological Survey on weed Flora and Diversity in Rice Fields of Chidambaram Block, T.N., India

A phytosociological survey was carried out to assess the varied weed flora and diversity in rice fields of Chidambaram block, Tamil Nadu, India. Chidambaram lies in low land habitat and the climate is subtropical. An average annual rainfall varies between 1200 to 1500 mm. The study has been done during 2020, Navarai season to determine the weed flora, species composition, density, frequency and important value index (IVI). To project the types of weed sps that are mainly affected the low land rice ecosystems. A total of 4 sedges, 3 grasses, 8 broad leaved weeds and 1 aquatic weed were detected. Sedges are most prominent weed flora found in the rice fields of Chidambaram block. The findings indicated that Cyperus difformis, Echinochloa colonum are the most abundant weeds in rice field followed by Cyperus rotundus, Echinochloa crusgalli, Leptonchloa chinensis, Eclipta alba and Sphenoclea zelyancia.

Seasonal Occurrence and Reproductive Suitability of Weed Hosts for Sweetpotato Whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), in South Georgia

Abstract South Georgia represents an area of intensive agricultural production where cultivated crops serve as hosts of the sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), throughout the year. In addition to cultivated hosts, there are numerous weed species present in the agricultural landscape that are undoubtedly responsible for supporting B. tabaci population development. This study provided information on the most abundant weed hosts of B. tabaci from this region. We evaluated 31 different weed species, of which 16 weed species are reproductive hosts with varying degrees of preference. Suitable weed hosts included cypressvine morningglory (Ipomoea quamoclit L.), nodding spurge (Euphorbia nutans Lag.), prickly sida (Sida spinosa L.), sharppod morningglory (Ipomoea cordatotriloba Dennst.), smallflower morningglory (Jacquemontia tamnifolia L.), tall vervain (Verbena bonariensis L.), and wild poinsettia (Euphorbia heterophylla L.). These species are highly abundant and therefore likely influence B. tabaci populations in the landscape. Other species including bristly starbur (Acanthospermum hispidum DC) and redweed (Melochia corchorifolia L.) were highly preferred by B. tabaci but not nearly as abundant in the landscape. Furthermore, we identified 10 very common weed species that were poor reproductive hosts including wild radish (Raphanus raphanistrum L.), Palmer amaranth (Amaranthus palmeri S. Watson), common ragweed (Ambrosia artemisiifolia L.), Florida pusley (Richardia scabra L.), and henbit (Lamium amplexicaule L.).

Effects of weed infestation on the productivity of hybrid and inbred rice varieties in Myanmar

AbstractDouble rice‐cropping areas in the dry and wet seasons have been increasing in Myanmar, and hybrid rice has been cultivated throughout the country. However, weeds are often not adequately managed. Therefore, the objective of this study was to investigate the effect of weed infestation on rice production of three hybrid varieties (Palethwe 1, Palethwe 3, and Palethwe Basmati) and three inbred varieties (Manaw Thu Kha, Shwe Thwe Yin, and Sin Thwe Latt) in the dry and wet seasons in a lowland rice field. In the dry and wet seasons, 19 ‐ 20 weed species were naturally infested into the fields. Limnocharis flava was the most abundant weed in both seasons. Weed dry weight and rice grain yield showed a negative linear relationship in both seasons. Manaw Thu Kha showed the highest yield loss in the un‐weeded fields in both seasons, while Sin Thwe Latt and Palethwe Basmati showed the lowest yield loss in the dry season and wet season, respectively. Sin Thwe Latt recorded the lowest yield loss of 30.21% on average in both seasons, and the highest yield loss of 60.37% was recorded for Manaw Thu Kha. The average rice grain yield loss of all the varieties in the un‐weeded fields was 64.37 and 33.66% for the dry and wet seasons, respectively. Thus, the yield loss in the dry season was 1.9‐times greater than that in the wet season. The present research suggests that adequate weed management is necessary for rice cultivation, especially in the dry season in Myanmar.

Impacts of long-term composted manure and straw amendments on rice-associated weeds in a rice–wheat rotation system

AbstractAs part of a long-term experiment to determine the impacts of composted manure and straw amendments (replacing 50% of chemical fertilizer with composted pig manure, wheat straw return combined with chemical fertilizer, and setting no fertilizer and chemical fertilizer-only as controls) on rice-associated weeds in a rice (Oryza sativaL.)–wheat (Triticum aestivumL.) rotation system, species richness, abundance, density, and biomass of weeds were assessed during years 8 and 9. Fertilization decreased the species richness and total density of rice-associated weeds but increased their total biomass. The species richness and densities of broadleaf and sedge weeds decreased with fertilization, while species richness of grass weeds increased only with straw return and density was not significantly affected. The shoot biomass per square meter of grass and broadleaf weeds was significantly higher with fertilization treatments than with the no-fertilizer control, while that of sedge weeds declined with fertilizer application. With fertilization, the densities of monarch redstem (Ammannia bacciferaL.) and smallflower umbrella sedge (Cyperus difformisL.) decreased, that of Chinese sprangletop [Leptochloa chinensis(L.) Nees] increased, and those of barnyardgrass [Echinochloa crus-galli(L.) P. Beauv.] and monochoria [Monochoria vaginalis(Burm. f.) C. Presl ex Kunth] were not significantly affected.Ammannia bacciferawas the most abundant weed species in all treatments. Whereas composted pig manure plus fertilizer resulted in higher density ofA. bacciferaand lower shoot biomass per plant than chemical fertilizer only, wheat straw return plus chemical fertilizer caused lower density and shoot biomass ofA. baccifera. Therefore, it may be possible that fertilization strategies that suppress specific weeds could be used as improved weed management program components in rice production systems.

Living mulch persistence in an apple orchard and its effect on the weed flora in temperate climatic conditions

AbstractReplacing herbicide fallow with alternative floor management can conserve soil and reduce agrochemical use in an orchard. Increased perennial weed resistance to foliar preparations has recently become an additional motivation to abandon herbicides. This study explores apple tree understory weed flora alteration after introducing Festuca ovina living mulch to the rows. Delayed cover crop sowing was tested as a possible approach to address the problem of high perennial weed dominance when a living mulch is introduced in the year of orchard establishment, in addition to reducing competition. The effect of replacing the M.9 dwarfing rootstock with the M.26 and P 60 semi‐dwarfing rootstocks to foster tree competitiveness was also investigated, and the influence of the mulch dominance on apple yield was analysed. Abundant perennial weed flora developed in the living mulch regardless of the mitigation strategy, and one of the cover crop cohorts exhibited unsatisfactory persistence when maintained under trees on P 60. This pattern was attributed to an interactive effect of shadowing by the more vigorous trees and by Glechoma hederacea and Artemisia vulgaris weeds, which abounded due to insufficient mowing frequency. More intensive tree understory management is recommended, especially in semi‐dwarf orchards, and G. hederacea should be studied more as a candidate mulch species, potentially superior to F. ovina.

The Biology of Canadian Weeds. 159.Capsella bursa-pastoris(L.) Medik.

Capsella bursa-pastoris (L.) Medik, shepherd’s purse, is a cosmopolitan summer or winter annual weed species distributed throughout temperate and subtropical regions of the world and is considered one of the most common plants on earth. It is an opportunistic annual that colonizes newly disturbed, open or dry environments and is ubiquitous in cultivated lands in Canada. In annual crops in western Canada, C. bursa-pastoris has been among the 20 most abundant weeds since the first weed surveys in 1970. It is most easily distinguished by its small white four-petalled flowers and its heart-shaped seed-pods, but exhibits considerable variation in leaf shape and flowering time. It has been used for food and medicine by numerous cultures. Its golden-brown seeds are produced in large numbers predominantly through self-pollination and can form a substantial seed bank, with reported values ranging to several hundred thousand seeds m−2. While seeds usually disperse near the mother plant, long-distance dispersal by attaching to vehicles, people and other vectors may be facilitated by its mucilaginous coat. Capsella bursa-pastoris does not produce fertile hybrids with other species of economic or ecological significance. It is generally well controlled by soil-applied and foliar (post-emergence) herbicides although its presence in agricultural fields may result in substantial yield loss, as documented in cole crops in North America and grain crops in Europe. The species can host a wide range of insect, nematode, fungal, viral, and bacterial pests that may damage crop species.

GC/TOF-MS-Based Metabolomics Reveals Altered Metabolic Profiles in Wood-Feeding Termite Coptotermes formosanus Shiraki Digesting the Weed Mikania micrantha Kunth.

Simple SummaryMikania micrantha Kunth is among the most invasive weeds in the world, causing extensive damage to both natural ecosystems and agroforestry systems. Mechanical removal is one of the most effective and straightforward approaches to controlling this weed, but this results in extensive lignocellulosic waste, and effective approaches to exploiting this abundant biomass are limited. Coptotermes formosanus Shiraki is not only an important subterranean termite pest species but also a considerable decomposer with the ability to digest lignocellulose. In this study, we evaluated the effects of a diet composed of M. micrantha leaves on C. formosanus workers. The workers increased their dietary intake when fed M. micrantha leaves, with a concomitant gradual increase in mortality rate. From the metabolic profiles, changes in metabolites and their related metabolic pathways suggested that termites can utilize M. micrantha-derived lignocellulose, but their antioxidant activity and signal transduction may be suppressed. Overall, this study identified key metabolites and pathways associated with the response of these termites to dietary changes and the effect of M. micrantha on termites.Effective approaches to exploiting the biomass of the abundant invasive weed Mikania micrantha Kunth are limited. Termites have been a focus of significant attention as mediators of biomass-processing owing to their ability to digest lignocellulose. Here, the GC/TOF-MS approach was employed to assess the effects of a diet composed of M. micrantha leaves on Coptotermes formosanus workers, with the growth performance of these workers also being assessed. The workers increased their dietary intake when fed M. micrantha leaves, with a concomitant gradual increase in mortality rate. A total of 62 differentially abundant metabolites and nine significantly affected pathways were found when comparing termites fed M. micrantha leaves to pinewood. Key metabolites, including carbohydrates, polyols, 4-hydroxyphenylacetic acid, and their related metabolic pathways, suggested that termites can digest and utilize M. micrantha-derived lignocellulose. However, changes in the tryptophan metabolism, tyrosine metabolism, and sphingolipid metabolism suggest an adverse effect of M. micrantha leaves on antioxidant activity and signal transduction in termites. Overall, this study identified the key metabolites and pathways associated with the response of these termites to dietary changes and the effect of M. micrantha on termites.

Weed Flora Dynamics in Maize (Zea mays L.) Field as Influenced by Cover Crop Types and Planting Densities at Jalingo, Northeast, Nigeria

Aim: Competition from weeds is an obstacle to profitable maize production. Knowledge of weed species limiting productivity is essential for sustainable management. A two years field experiment was conducted to evaluate the effect of a leguminous cover crop, akidi (Vigna unquiculata sub-sp sequipedalis) and two non-leguminous cover crops (melon and sweet potato) planted at three densities on weed flora composition and shift in maize at Jalingo, North-eastern Nigeria.
 Study Design: There were 11 treatments replicated three times in a randomized complete block design.
 Methodology: Low, moderate and high densities (20,000, 30,000 and 40,000 stands/ha respectively) of Akidi, Melon and Sweet potato (A1, A2, A3, M1, M2, M3, S1, S2, S3) with weeded (C1) and unweeded (C2) checks constituted the treatments laid out in a randomized complete block design replicated three times. Weed flora abundance, percentage density, percentage frequency, frequency index and percentage contributions were determined from a 50cm x 50cm quadrat thrown twice per plot at various phases of maize growth.
 Results: Thirteen weed families made up of 11 broad leaves, one grass and one sedge were identified. The abundance was in the order Broad leaf > Grass > Sedges. The most abundant weed species were: Imperata cylindrica L (3.8), Mucuna utilis (3.0), Oldenlandia herbacea L. (2.6) Sida acuta Burm F, Tridax procumbens L. (2.5 each), Leucas martinicensis, Pennisetum pedicellatum (2.3 each). Commelina benghalensis, Cyperus difformis (3.5), Digitaria horizontalis, Fimbristylis littoralis (2.8 each). The influence of selected cover crops on individual weed percentage the contribution shows: Commelina benghalensis ( C2<C1 < M <S< A), Euphorbia hyssopifolia (C2<M/S < A<C1), Euphorbia heterophylla (M<S<A), Leucasmartinicensis (C1<C2<M<A<S), Mucunautilis (S<M<C1<C2<A) and Sida acuta (M<S<A<C2<C1) while grassy weeds, Imperata cylindrical (A<C2<S<M), Pennisetum pedicellatum (A<C2), Digitaria horizontalis (C1/ C2< A < M <S), Kyllinga squamulata (M/S <C2<A <C1). Commelina spp. increased in status from an accessory (21.2%) to abundance (66.7%) while others increased from rare to accessory (from 0.0 to 20-40%).
 Conclusion: Akidi was more effective on broad-leaved weeds while melon and sweet potato were more effective on grasses and Commelina benghalensis need to be monitored.

Creating ultrahigh surface area functional carbon from biomass for high performance supercapacitor and facile removal of emerging pollutants

Recent decade has seen enormous interest in developing cost effective, simple and greener method of utilizing naturally abundant and renewable resources to mitigate the concerns relating contaminated water sources and store green energy. Carbon materials derived from biomass have drawn great attention because of their abundance, easy processability, tunable surface properties and relatively low cost. Present work demonstrates the conversion of abundant and toxic weed, Parthenium hysterophorous to porosity enriched ultrahigh surface area activated carbon with a surface area of 4014 m2/g and a large porous volume of 2.0419 cm3/g. The optimized carbon materials before and after activation showed crumpled sheet-like morphology with oxygenated functionalities (C/O = 6.352) as confirmed by different analytical tools. Electrochemical studies revealed that the supercapacitor device assembled using the as prepared carbon material manifest an significant specific capacitance of 270 F/g, exhibiting excellent capacity retention of 98.5 % even after 30,000 cycles at an increased current density of 10 A/g. Further, a membrane was prepared using functional carbon material for the removal of different organic pollutants such as dyes (methylene blue, malachite green, eriochrome black T, congo red) and pharmaceutical wastes (paracetamol, ciprofloxacin) from aqueous media. The functional carbon based membrane showed high rejection for cationic dyes (93–99.5%) comparing to anionic dyes (46–67%) with a flux rate in the range of 820–840 Lm-2h−1 and maximum adsorption capacity of 194 mg/g for methylene blue dye. Similarly, for cationic pharmaceutical wastes higher rejection (90–95%) was achieved with an average flux of 830 Lm-2h−1. Moreover, recyclability studies of the membrane affirmed a retention of 91.6% rejection of methylene blue even after 10 consecutive cycles without compromising the flux rate which confirmed the suitability of the toxic weed derived functional carbon as a sustainable alternative for water purification in a continuous flow method.

Climate-smart agriculture practices influence weed density and diversity in cereal-based agri-food systems of western Indo-Gangetic plains

Climate-smart agriculture (CSA)-based management practices are getting popular across South-Asia as an alternative to the conventional system for particular weed suppression, resources conservation and environmental quality. An 8-year study (2012–2013 to 2019–2020) was conducted to understand the shift in weed density and diversity under different CSA-based management practices called scenarios (Sc). These Sc involved: Sc1, conventional tillage (CT)-based rice–wheat system with flood irrigation (farmers’ practice); Sc2, CT-rice, zero tillage (ZT)-wheat–mungbean with flood irrigation (partial CA-based); Sc3, ZT rice–wheat–mungbean with flood irrigation (partial CSA-based rice); Sc4, ZT maize–wheat–mungbean with flood irrigation (partial CSA-based maize); Sc5, ZT rice–wheat–mungbean with subsurface drip irrigation (full CSA-based rice); and Sc6, ZT maize–wheat–mungbean with subsurface drip irrigation (full CSA-based maize). The most abundant weed species were P. minor > A. arvensis > M. indicus > C. album and were favored by farmers’ practice. However, CSA-based management practices suppressed these species and favored S. nigrum and R. dentatus and the effect of CSAPs was more evident in the long-term. Maximum total weed density was observed for Sc1, while minimum value was recorded under full CSA-based maize systems, where seven weed-species vanished, and P. minor density declined to 0.33 instead of 25.93 plant m−2 after 8-years of continuous cultivation. Full CSA-based maize–wheat system could be a promising alternative for the conveniently managed rice–wheat system in weed suppression in north-west India.

Composition of weed communities in seasonally flooded rice environments in East Africa is determined by altitude

Weeds are major biotic constraints to rice production worldwide. Compared to other sub-regions, weed communities of rice are not well described for East Africa and there is limited information on environmental factors affecting the distribution of species. This study aimed to address these knowledge gaps. Seasonally flooded rice production fields of 31 sites in Rwanda, Tanzania, Kenya and Uganda, across three altitude classes (Low: <200 m; Medium 200–1,000 m; High: >1,000 m), were surveyed for weed species using quadrats. Data analyses involved multivariate approaches, non-parametric Kruskal–Wallis tests and logistic regressions, followed by calculation of ranked species abundance and Shannon Wiener Index diversity analyses. A total of 286 weed species, belonging to 59 families, were recorded with 42 species not previously reported as lowland rice weed in the sub-region. Twenty-four species were identified as abundant across altitudes. Weed species diversity was higher at medium altitudes compared to high and low altitudes. Significant patterns of floristic distinction between altitudinal classes were observed, with 80% of dissimilarity. The high altitude was dominated by Echinochloa colona, Leptochloa squarrosa and Sphaeranthus suaveolens, the medium altitude was dominated by Crassula granvikii, Pycreus lanceolatus and Ageratum conyzoides while the low altitude was dominated by E. colona, Cyperus difformis and Cyperus esculentus. The weed species composition of seasonally flooded rice fields in East Africa is diverse. Identification of a limited group of (24) commonly abundant weed species as well as the articulation of altitude-specific weed species groups will facilitate the development of better tailored weed control programmes.

Weeds in Florida Sugarcane as Host Plants for Three Species of Rice Stink Bugs (Hemiptera: Pentatomidae)

Weeds in Florida Sugarcane as Host Plants for Three Species of Rice Stink Bugs (Hemiptera: Pentatomidae)

Weed Species Dominance and Abundance in Tea (&amp;lt;i&amp;gt;Camellia sinensis&amp;lt;/i&amp;gt; L.) Plantation of Southwest Ethiopia

Tea (<i>Camellia sinensis</i> L.) is one of the most popular beverage crops. Among tea production constraints, weed is one of the detrimental factors in tea productions in Ethiopia. For the possibility of developing weed management method determining the dominant and abundant weed species is highly important to identify and prioritize the most noxious and prevalent weed that associated with tea production in the country. Weed flora survey was conducted in two different tea estate farms Wushwush and Gumero tea plantations in 2019/20 cropping seasons. The field survey was done according to the quantitative survey method by using 1m² quadrate size. Weeds present in each quadrate were counted and identified to species level. Weed abundance, dominance, frequency and similarity index was determined at two tea producing locations. A total of 63 weed species were identified from assessed tea plantation farms. The result revealed that 61.3% and 71.9% of broad leaf weed was recorded at Wushwush and Gumaro tea plantation, respectively. Only, two (6.5%) parasitic weed species were recorded at Wushwush. The most prevalent and abundant weed species at Wushwush was <i>Ageratum conyzoides</i> followed by <i>Hydrocotyle americana</i>, whereas, <i>H. americana</i> was the most dominant species at Gumero tea plantation. Generally, from survey results, the weed flora composition was similar in both assessed areas, as its similarity index resulted above 70%. Hence, similar weed management methods should be recommended for both locations.

Weed Survey Associated in Tobacco (Nicotiana tabacum L.) in Bilatte Tobacco Farm, Ethiopia

An in-field weed survey method was conducted to estimate the most frequently, density and abundance weed species present in Bilatte tobacco farm, Ethiopia during 2014 totally covered approximately 145 hectares. During study period a total number of 14 weed species belonging to 06 monocot and 08 dicot families were recorded out of 7 families of weed reported form study site. The most predominate was shown by monocot Poaceae having 4 weed species followed by dicot family Composite having 3 weeds. The families Cyperaceous, Solanaceae and Amaranthaceous each having 2 weeds, and the family Papaverceae represented by 1 weed. Based on % of frequency Cyperus esculentus (sedges) family Cyperaceous was 99.30. The data showed that Cynodon dactylon and Digitaria abyssinica belong to family Poaceae and Cyperus esculentus family Cyperaceous were the most abundant weed with a density of 35.9, 14 and 12 of plant m-2 respectively. Relative abundance values quantify the overall weed problem posed by specie Cyperus esculentus that had higher relative abundance was 98.97. The importance value index indicated that Cyperaceous and Poaceae families can be considered the great potential to cause reduce tobacco production. Whereas, Solanium nigrum and Datura stramonium were observed with least population density 0.00 and 1.03 plant m-2, least frequently 2.7 and 13.51 %, least relative weed abundance, 0.07 and 1.03 with importance value index 2.8 and 14.8 occurring weed respectively.

Individual-based 3D modelling of root systems in heterogeneous plant canopies at the multiannual scale. Case study with a weed dynamics model

Reducing pesticide use in agriculture is essential but involves shifting towards more complex agroecosystems. Plant canopies are expected to be more heterogeneous because a more abundant weed flora is likely to remain in low-herbicide fields, and because intercropping (i.e. mixing various crops species or varieties) is a promising option to reduce chemical inputs. Simulation models are useful to understand and design complex agroecological cropping systems, but they rarely represent the root systems of plants. However, belowground processes, such as competition for soil resources or infection by root-parasitic plants, are key determinants of the structure of plant communities. The aim of our study was to develop a model that simulates heterogeneous 3D individual-based crop-weed canopies from cropping system and pedoclimate and that will ultimately be used to design agroecological cropping systems. Therefore, we (1) connected a root system model (RSCone) to a weed dynamics model (FlorSys) in order to include both above and belowground parts of plants, (2) evaluated the prediction quality of our model, and (3) analysed the influence of species parameters on potential soil-resource uptake and root infection by parasitic plants. We used the well-known allometric relationship between root and total plant biomass to connect RSCone and FlorSys, and we created new formalisms to model the effect of soil compaction on root growth. Our model was shown to correctly predict long-term weed dynamics in various cropping systems. From step 3), we characterized crops and weed communities that are potentially competitive for soil resources and most likely to be infected by parasitic plants, and we deduced agronomic recommendations. For example, species emerging and occupying the soil quickly were the most likely to relay broomrape infestation and control of such species should take precedence. Although we focussed on crop-weed competition, our approach can be applied to other heterogeneous canopies, for designing crop mixtures for example.

Seed Yield and Yield Components of Sesame as Affected by Various Weed Control Methods

Weed control strategy greatly influences on weed infestation and yield of sesame. An experiment was conducted at Regional Agricultural Research Station, Ishurdi, Pabna during Kharif-1 season of two consecutive years 2015-16 and 2016-17 to find out the suitable weed control methods in sesame. It comprises five weed control methods viz., Application of Panida (T1), Application of Panida with one hand weeding at 20 DAE (T2), One hand weeding at 20 DAE (T3), Two hand weedings at 20 and 40 DAE (T4) and Control (no weeding) (T5 ). The experiment was laid out in a randomized complete block design with three replications. Among the weed species, Cyperus rotundus and Digitaria sangunalis were the most abundant weeds. Application of Panida with one hand weeding at 20 DAE (T2) gave the lowest weed density, weed biomass and the highest weed control efficiency followed by application of Panida (T1) in both years. Weed biomass influenced negatively on plant height, number of capsule plant-1, seed yield and stalk yield. The maximum seed yield and stalk yield were also obtained from T2 which was statistically similar to T1 treatment and the minimum seed yield from T5. Economic analysis indicated that T2 gave higher gross return but T1 provided higher gross margin and benefit cost ratio. The treatment, T4 showed higher total variable cost due to the high cost of labour for hand weeding with the increase of variable cost, which affected the marginal return and benefit-cost ratio. However, based on the economic point of view, application of Panida in pre-emergence condition (T1) was a profitable and suitable weed control method in summer sown sesame.&#x0D; Bangladesh Agron. J. 2020, 23(1): 107-116

Do ecological specialization and functional traits explain the abundance–frequency relationship? Arable weeds as a case study

AbstractAimThe abundance–frequency relationship (AFR) is among the most‐investigated patterns in biogeography, yet the relative contributions of niche‐based processes related to ecological strategies, and of neutral processes related to spatial colonization–extinction dynamics, remains uncertain. Here, we tested the influences of ecological specialization and functional traits on local abundance and regional frequency, to determine the contribution of niche‐based processes.LocationFrance and the UK.TaxonVascular plants.MethodsWe used two arable weed surveys covering 1,544 fields in Western Europe (France, UK), along with functional traits related to resource acquisition, resource requirements, flowering phenology and dispersal. We quantified specialization both to arable habitat and to individual crop types, and performed phylogenetic path analyses to test competing models accounting for direct and indirect relationships between traits, specialization, abundance and frequency. We performed the analyses for all species in each country, as well as for a subset of the most abundant species.ResultsLocal abundance of weeds increased with their regional frequency, but the relationship became negative or null when considering only the most abundant weeds. Specialization to arable habitat and to individual crop type either had a similar or opposite effect on regional frequency and local abundance explaining these positive and negative relationships, respectively. Regional frequency was not directly explained by any trait but indirectly by resource requirement traits conferring specialization to the arable habitat. Conversely, high local abundance was directly related to low seed mass, high SLA, early and short flowering.Main conclusionsDirect/indirect effects of functional traits on local abundance/regional frequency, respectively, supports a significant role of niche‐based processes in AFR. Neutral spillover dynamics could further explain a direct linkage of abundance and frequency. Similar causal paths and consistent influences of traits on specialization and abundance in the two studied regions suggest genericity of these findings.

Qualitative and Quantitative Assessment of Common Weed Species in West Gondar Sesame Growing Area, Ethiopia

Weeds compete with crops grown for resource limits such as water, nutrients, and light. Weed infestation is one of the major factors limiting sesame production, as its seedlings grow slowly during the first few weeks making it a weak competitor at earlier crop growth stages. Weed induced sesame yield reductions of up to 65 percent, and a need for a crucial weed-free duration of up to 50 days following planting. Weed surveys are useful for determining the occurrence and relative importance of weed species in crop production systems. Weed survey on a farm basis is needed to establish efficient weed management and decision making mechanisms and to evaluate weed control measures. Therefore this survey was conducted to assess qualitative and quantitative weed species in sesame growing areas of west Gondar, Ethiopia. Weed survey was conducted in 2012 at Metema and 2013 main cropping season at Metema, Tach Armachiho, and Mirab Armachiho district. data on weed species type and count were taken along the diagonal with 50cm x 50cm quadrate at a 15-meter interval at three points. Visual identification, manuals, photographs, leaflets, and books were used for identifying weed species. They conducted interviews with farmers, development agents, and district experts working in the region. Weed species compositions were analyzed by frequency, abundance, dominance, and similarity index. In the districts, 31common weed species or groups of species from 17 families were recorded. Ipomea cordofana Br., Grass spp’, Commelina benghalensis L. Andropogon abyssinicus (Fresen) R.Br., Boerhaavia erecta L., Corchorus olitorius L.kudra, Corchorus trilocularis L., Leucas martinicensis (Jacq) ait.f. and Ipomea triloba are the most prevalent, abundant, and important weeds in sesame fields in north Gondar. As to this on-farm and practical training on identification and demonstration management options should be given on the low land of north Gondar farmers.

Future distribution of invasive weed species across the major road network in the state of Montana, USA

Invasive plant species are a significant global problem, with the potential to alter structure and function of ecosystems and cause economic damage to managed landscapes. An effective course of action to reduce the spread of invasive plant species is to identify potential habitat incorporating changing climate scenarios. In this study, we used a suite of species distribution models (SDMs) to project habitat suitability of the eleven most abundant invasive weed species across road networks of Montana, USA, under current (2005) conditions and future (2040) projected climates. We found high agreement between different model predictions for most species. Among the environmental predictors, February minimum temperature, monthly precipitation, solar radiation, and December vapor pressure deficit accounted for the most variation in projecting habitat suitability for most of the invasive weed species. The model projected that habitat suitability along roadsides would expand for seven species ranging from + 5 to + 647% and decline for four species ranging from − 11 to − 88% under high representative concentration pathway (RCP 8.5) greenhouse gas (GHG) trajectory. When compared with current distribution, the ensemble model projected the highest expansion habitat suitability with six-fold increase for St. John’s Wort (Hypericum perforatum), whereas habitat suitability of leafy spurge (Euphorbia esula) was reduced by − 88%. Our study highlights the roadside areas that are currently most invaded by our eleven target species across 55 counties of Montana, and how this will change with climate. We conclude that the projected range shift of invasive weeds challenges the status quo, and requires greater investment in detection and monitoring to prevent expansion. Though our study focuses across road networks of a specific region, we expect our approach will be globally applicable as the predictions reflect fundamental ecological processes.

English

Soil fertility transience and weed management are often among decried impediments undermining agricultural productivity in many tropical countries. A study aiming at transforming baffling problems of abundant weed biomasses especially that of Panicum maximum (T1), Tryps-acum laxum (T2) and Pueraria javanica (T3), often cause of crop yield loss into advantage to enhance soil fertility, increase crop productivity as well as help tackle weed issue was initiated in the region of Kisangani. To do this, a 90-day composting experiment involving a mono factorial randomized complete block design including three replications and three treatments of above mentioned weed biomasses was conducted from 23rd March to 23rdJune 2013. The results of analysis of variance showed significant differences among treatments for pH H2O (p&le;0.013) and potassium content (p&le;0.001). The three composts demonstrated high nutrient content level in total organic carbon, nitrogen and potassium able to restore soil fertility. Moreover, the study revealed that the pH values of all the composts were closer to neutral on average and can be used to fix the recurrent issue of soil acidity in the region. Finally, the results showed that the species were able to produce sufficient compost mass with 41.5, 36.3 and 30.9% of initial mass loss respectively for T1, T2 andT3 in a relatively short time. Key words: Soil fertility transience, compost, weed management, agricultural productivity, DR Congo. &nbsp