Estimating Carbon Capture Potential of Fallow Weeds in Rice Cropping Systems

Weeds occurred during the fallow season can well perform the function of carbon(C)capture due to receiving little human disturbance.This study aimed to evaluate the C capture potential of fallow weeds in rice(Oryza sativa L.)cropping systems.A six-region,two-year on-farm investigation and a three-year tillage experiment were conducted to estimate C capture in fallow weeds in rice cropping systems.The on-farm investigation showed that the average mean C capture by fallow weeds across six regions and two years reached 112 g m^(-2).The tillage experiment indicated that no-tillage practices increased C capture by fallow weeds by 80%on average as compared with conventional tillage.The results of this study not only contribute to an understanding of C capture potential of fallow weeds in rice cropping systems,but also provide a reference for including fallow weeds in the estimation of vegetative C sink.

Fungal Flora on Weeds in the Cashew (Anacardium occidentale L.) Orchard in Côte d’Ivoire

Since 2015, Côte d’Ivoire has been the world’s largest cashew producer. However, cashew orchards in Côte d’Ivoire are infected by fungal diseases that weaken production. And the contribution of weeds to the spread of these diseases is not yet understood. This study was initiated with the aim of establishing the role of weeds in the proliferation of pathogenic fungi in orchards. It consisted of a survey of weeds showing disease symptoms in cashew orchards in Côte d’Ivoire from February 2021 to July 2022. The itinerant method was used for the weed inventory. Symptomatic leaves were collected and sent to the laboratory for diagnosis on PDA (Potatoes Dextrose Agar) medium. In total, 50 species in 46 genera and 23 families were recorded. Laboratory diagnosis of the samples showed that 80% of the weeds identified harboured pathogenic fungi. The highest infection rates were obtained on Danielia oliveri R. (99.33% to 100%), Vitellaria paradoxa G. (100%), Pterocarpus erinaceus P. (83.91% to 99.33%), Micuna pruriens L. (98.33% to 100%) and Isoberlinia doka C. et S. (56.33% to 100%). The diagnosis revealed the presence of Lasiodiplodia sp, Colletotrichum sp, Pestalotia sp, Alternaria sp and Curvularia sp on weeds in the cashew orchard in Côte d’Ivoire.

Influence of Adjuvants on the Efficacy of Tolpyralate plus Atrazine for the Control of Annual Grass and Broadleaf Weeds in Corn with and without Roundup WeatherMAX^®

Tolpyralate is a new HPPD-inhibiting herbicide that is efficacious on annual grass and broadleaf weed species in corn. For maximum herbicide performance of tolpyralate, it is recommended that atrazine is tank mixed with tolpyralate along with the adjuvants methylated seed oil concentrate (MSO) plus urea ammonia nitrate (UAN). A common use pattern of tolpyralate plus atrazine will be in a tank mix with Roundup WeatherMAX®due to the high proportion of corn acres that are seeded to Roundup Ready®hybrids in Eastern Canada. There is no information in the peer-reviewed literature if the adjuvant system in Roundup WeatherMAX®is adequate for optimal herbicide performance of tolpyralate plus atrazine, or if MSO and UAN are still required. Six field trials were conducted over two years near Ridgetown and Exeter, ON, Canada to determine if adjuvants are still required when tolpyralate plus atrazine is tank mixed with Roundup WeatherMAX®in corn. Tolpyralate plus atrazine plus MSO and Roundup WeatherMAX®plus tolpyralate plus atrazine provided excellent control of velvetleaf, pigweed spp, common ragweed, lambsquarters, ladysthumb, wild mustard, flower-of-an-hour, barnyardgrass and green foxtail in this study. Results of this study show that in the absence of Roundup WeatherMAX®, weed control with tolpyralate plus atrazine was improved substantially with the addition of MSO;however, there was little to no increase in weed control with the addition of UAN. When tolpyralate plus atrazine was co-applied with Roundup WeatherMAX®, there was no improvement in weed control with the addition of MSO and/or UAN.

Evaluation of soil flame disinfestation(SFD) for controlling weeds,nematodes and fungi

Soil flame disinfestation(SFD) is a form of physical disinfestation that can be used both in greenhouses and on field crops. Its use for soil disinfestation in different crop growing conditions makes it increasingly attractive for controlling soilborne pathogens and weeds. But little is known about the effect on weeds and soilbrone diseases. This study reports on greenhouses and field crops in China that determined the efficacy of SFD to control weeds, nematodes and fungi. It also determined the impact of SFD on the soil physical and chemical properties(water content, bulk density, NO3^–-N content, NH4^+-N content, conductivity and organic matter) in three field trials. A second generation SFD machine was used in these trials. SFD treatment significantly reduced weeds(>87.8%) and root-knot nematodes(Meloidogyne incognita)(>98.1%). Plant height and crop yield was significantly increased with SFD treatment. NO3^–-N and NH4^+-N increased after the SFD treatment, and there was also an increase in soil conductivity. Water content, bulk density and organic matter decreased significantly in the soil after the SFD treatment compared to the control. Soil flame disinfestation is a potential technique for controlling weeds and diseases in greenhouses or in fields. SFD is a non-chemical, safe, environmentally-friendly soil disinfection method.

Herbicidal activity of Aureobasidium pullulans PA-2 on weeds and optimization of its solid-state fermentation conditions

Fungal strain PA-2 was isolated from infected poplar leaves from the Ping’an District, Haidong City of Qinghai Province, China. Based on the culture characteristics and the internal transcribed spacer(ITS) sequence of its 16S r DNA, the strain was identified as Aureobasidium pullulans. The culture and metabolites of strain PA-2 showed high herbicidal potential to five tested weeds Galium aparine var. tenerum, Chenopodium album, Malva crispa, Polygonum lapathifolium and Avena fatua. For the in vitro test, 5 days after the detached leaves were inoculated with PA-2 culture, all leaves infected by the hyphae and became black and rotten. For the in vivo test, a metabolite filtrate of PA-2 culture was sprayed over the living weed plants, and five days after inoculation, the weed plants became withered and necrotic. Seven days after inoculation, the fresh weight reductions of G. aparine var. tenerum, C. album, M. crispa, P. lapathifolium and A. fatua were 87.25, 78.46, 82.25, 62.11, and 80.27%, respectively. Galium aparine var. tenerum and M. crispa exhibited significant reductions in fresh weight. The bio-safety test on the five crops showed no significant plant height reductions, which was also observed for wheat(Triticum aestivum), faba bean(Vicia faba), and barley(Hordeum vulgare). By contrast, oilseed rape(Brassica napus) and pea(Pisum sativum) exhibited light spots but no significant reductions in plant height. These results indicated that A. pullulans could be a potential microbial herbicide for the control of the target weeds in crops. Optimization of the carbon and nitrogen sources for cultural media and substances for solid-state fermentation indicated that PA-2 had better colony growth and spore production with the optimal carbon source of glucose(C4), nitrogen source of soybean flour(N2), and the optimal substance was wheat bran. The results in this study provide useful information for the development ofA. pulluans PA-2 as an herbicide for bio-control of the weed.

A Review of Research Directions and Research Methods of Farmland Weeds

Farmland weeds are an important part of farmland ecosystems.Research on farmland weeds is one of the major research fields in agricultural ecology.It is of great significance for achieving high yield,high quality and high efficiency in agriculture.In recent years,research on farmland weeds has focused on investigation of weed communities,research on weed seed banks,and research on weed control.These three research directions complement each other.Among them,the investigation work of weed communities and the research of weed seed banks are helpful for us to grasp the occurrence of farmland weeds more accurately and provide references for the control of farmland weeds.This article summarizes the research directions of farmland weeds in recent years(weed community investigation,weed seed bank,weed control)and the research methods used,provide reference value for the follow-up research work of farmland weeds,and provide theoretical support for promoting the development of rural ecological industry and building beautiful villages.

Several Exotic Harmful Weeds in Beilun Port of Ningbo

An investigation was carried out in wharves, inspection yards, processing plants in Beilun Port and the surrounding areas. Five kinds of exotic harmful weeds were discovered and collected, and they were described and analyzed.

Use of Gramoxone 20SL (Paraquat) Prior to Land Preparation in Controlling Aquatic Weeds in Wetland Areas of Bangladesh

Emergent aquatic weeds present in the monocropped fresh water wetland area of Bangladesh create a hazard in land preparation by developing dense stands. A field experiment was conducted at the farmers’ field of two villages namely Mahilara and Kashemabad under Gournadi Upazila of Barisal district, Bangladesh during October 2012 to evaluate the efficacy of Gramoxone 20SL (Paraquat) in controlling emergent aquatic weeds and to find out an appropriate dose of this herbicide. Three doses of Gramoxone 20SL at 1.96 l·ha-1, 2.00 l·ha-1 and 2.04 l·ha-1 were tried with an untreated control. All treatments were laid out in a randomized complete block design and replicated thrice. There were 8 different emergent weed species infesting the field among which the most dominant weed species were Eichhornia crassipes, Pistia stratiotes, Enhydra fluctuans, Monochoria vaginalis, Echinochloa crus-galli. The results revealed that, weed control efficiency was significantly affected by different herbicidal treatments. The treatments, Gramoxone 20SL at 2.00 l·ha-1 and 2.04 l·ha-1 were controlled in all the emergent aquatic weeds more than 85% infesting both the sites. Application of non-selective herbicide Gramoxone 20SL at 2.00 l·ha-1 prior to land preparation was most effective to suppress weed dry masses in both the site resulting reduced land preparation cost up to 78.93% as compared to manual weed control.

Weeds of Wheat Crop and Their Control Strategies in Dera Ismail Khan District, Khyber Pakhtun Khwa, Pakistan

This study is based on research work conducted during 2008-2010 inDera Ismail Khan, KPK,Pakistan. The research area was extensively surveyed to investigate weed species. About 32 weed species, belonging to two monocot and thirteen dicot families, were collected from the study area. Plants were identified with the help of available literature and by comparing with the already identified plant specimens of the herbarium ofQuaid-i-AzamUniversity,Islamabad,Pakistan. Data inventory constitutes botanical name, vernacular name, English name, family, and flowering and fruiting period. Phalarus minor, Rumax dentatus, and Chenopodium album were the dominant weeds in the study area having comparatively higher relative weed density. Weeds having tough competition with wheat crop for light, moisture, and nutrients adversely affect wheat production. Hence, a constant effort is needed to keep the weed population under control. Many methods of weed control and eradication have been devised but chemical control is the most effective one. However, it may have some environmental consequences if not handled properly.

Occurrence and Control of Weeds in Abandoned Fields in Central Hunan

[Objectives]This study was conducted to clarify the occurrence of weeds,and give relevant comprehensive control suggestions accordingly.[Methods]The species and community characteristics of weeds in abandoned rice fields in central Hunan were investigated and analyzed.[Results]There were 75 species of weeds in the abandoned farmland in central Hunan,belonging to 66 genera,27 families.Among them,22 species had a relative abundance of more than 5%.According to the different water environments of abandoned fields,there were differences in the types and structures of weeds.They succeeded to wetland vegetation types and dryland vegetation types respectively.Species grown in the original farmland still exist in abandoned fields,but they were mainly invaded by field weeds,such as Digitaria sanguinalis,Eleusine indica,Panicum acroanthum,Bidens pilosa,and Xanthium sibiricum.[Conclusions]This study lays a foundation for fully guaranteeing the actual results of re-cultivation of abandoned land in rural areas.

Farmers’ Understandings of Weeds and Herbicide Usage as Environmental Influences on Agricultural Sustainability

Little comparative research has specifically used farmers’ understandings of agricultural weeds and herbicides usage as important indicators of their environmental decision making and behaviours. This paper proposes that “organic’ farmers”, already attuned to environmental ideas, may be more likely to have favourable understandings and behaviours towards agricultural weeds as an integral part of environmentally sustainable agricultural farming systems than “conventional” farmers. Using a behavioural approach, the ways in which farmers’ (situated in central-southern England) understandings influence their environmental behaviours were examined. Most “conventional” farmers’ fields were kept relatively weed-free through herbicide usage. This contrasted with “organic” farmers having less concern about removal of weeds (with their associated invertebrates and seeds) which they understood contributes significantly towards biodiversity and agricultural sustainability. A remarkably high 92 per cent of “organic” farmers were critical of “conventional” farmers’ using herbicides and pesticides, asserting that lack of pesticide and herbicide usage as core reasons for their sustainability. This contrasted with most “conventional” respondents who claim they used as few chemicals as practicable to minimise environmental damage to soil and water, while maintaining adequate crop levels. Nevertheless, such environmental understandings and behaviours may not always be indicative of any differences that may be found between those farmers commonly classified as “organic” and “conventional” in the UK as a whole.

Analysis of the Impact of Aquatic Weeds in the Shire River on Generation of Electricity in Malawi: A Case of Nkula Falls Hydro-Electric Power Station in Mwanza District, Southern Malawi

A study was carried out to analyse the extent to which diverse species of aquatic weeds that have proliferated in the Shire River in Malawi in recent years affect the generation of electricity at Nkula Hydro-Electric Station in Mwanza District of the southern region of the country. Specifically, the study endeavoured to establish whether frequent power interruptions that Malawi is facing are the result of the problems caused by aquatic weeds in the Shire River which are believed to disturb proper functioning of the machines at the power station. Study results revealed that as much as the aquatic weeds impede power generation such as blocking the turbines, problems of low power generation that result into frequent and persistent load shedding are not entirely due to aquatic weeds. Problems of inefficient machines and shut down of machines are due to serving, which appeared to be the major cause.

Impacts of Different Weeding Methods on Weeds Control in Tobacco Fields in Anshun City

[Objective] The paper was to explore weed control measures in tobacco fields in Anshun City. [Method] Different treatments on weed control were conducted in tobacco fields in Anshun City, Guizhou Province, from 2017 to 2019. [Result] Various treatments had no negative effect on tobacco plant growth in the field, and had different degrees of control effects on five dominant weeds, including Digitaria sanguinalis, Setaria viridis, Fagopyrum dibotrys, Commelina communis and Chenopodium album. White mulching film and 50% butralin·clomazone EC 160 m L/667 m^(2) + white mulching film had the worst performance, which had extremely significant or significant differences with other treatments. There was no sig-nificant difference among most treatments, and the overall effects were comprehensive(multi-factor) treatment > double factor treatment > single factor treatment. [Conclusion] Combination control is recommended in practical tobacco production.

Effects of Methylated Soybean Oil Adjuvant on Fomesafen Efficacy to Weeds

Tank-mix adjuvant has the potential to improve the weed control efficacy of post-emergence herbicides. In order to study the synergistic effect of adjuvant, the effects of different rates of fomesafen alone or applied methylated soybean oil adjuvant(MSO) were sprayed on redroot pigweed, abutilon and black nightshade under greenhouse condition. The results showed that fomesafen had different performance on the three weeds, and MSO adjuvant could effectively increase the control. The nightshade control was lower than other two weeds with all the fomesafen doses from 131.25 to 506.25 ga.i. · hm-2 with or without adjuvant. The control of abutilon was between the black nightshade and the redroot pigweed, and had better control at 375 ga.i. · hm-2 with adjuvant or 506.25 ga.i. · hm-2 alone or with adjuvant respectively. The results indicated that mixing adjuvant with fomesafen improved the control on weeds, especially at the low rate. Black nightshade was more difficult to control. The redroot pigweed had the most susceptibility to fomesafen alone or with adjuvant.

Reduced Rates of Metribuzin and Time of Hilling Controlled Weeds in Potato

The current emphasis on reducing herbicide applications has led to an increase in alternative weed control measures. Field experiment was conducted in the spring of 2014 to examine the effect of hilling-time and reduced-rates of metribuzin and their combinations on weed infestation in potato, and to determine their impact on potato yield. Metribuzin at 0.35, 0.56, or 0.75 kg ai/ha with or without hilling 6, 7, and 8 weeks after planting (WAP) were used. Weed count, weed control visual rating, weed dry weight, potato plant height, number of shoots and leaves, root dry weight, and potato yield were collected. Results showed that metribuzin, at all tested rates, with or without hilling significantly reduced weed infestation after 50, 70, and 110 days after planting (DAP) compared to the check. Best results were obtained by a combination of metribuzin at all tested rates with hilling 6, 7, and 8 WAP. The results suggest that long season weed control and high marketable yield could be achieved by metribuzin at 0.35 kg ai/ha (53% reduction in metribuzin) supplemented with hilling (6 WAP). None of the treatments was toxic to potato plants compared to the hand-weeded plots.

Phytosociological Survey of Weeds in Areas of Crop-Livestock Integration

The dynamics of the weeds in the areas of crop-livestock integration is constantly changing depending on the various uses of the area. This study identified and quantified the floristic composition of weeds in areas of integration of maize for silage with Urochloa ruziziensis cv. Common at different densities of grass (0, 4 and 10 kg·ha-1) to grazing of beef cattle. The experimental design was completely randomized. A square of side0.5 m(0.25 m2area) was launched 24 times in each study area. The survey was conducted at the grain filling stage of maize. The specie contained in each frame were identified and counted. The phytosociological survey identified 9 families of weeds in areas assessed, with 7 families in every area of integrated cultivation maize with Urochloa ruziziensis at densities of 10 kg·ha-1 and 4 kg·ha-1 and 8 families in the area of maize cultivated alone. The Asteraceae family was the most represented in number of species. Sida spp (Malvaceae) showed greater potential to cause damage to maize. Urochloa ruziziensis at planting density of 10 kg·ha-1 provided greater competition with weeds in the integration with maize.

Diversity and Chemical Composition of Weeds in Sand-Filled Mangrove Forest at Eagle Island, Niger Delta, Nigeria

Mangroves are habitat specific and grow mainly in swampy soil, but due to anthropogenic activities (e.g. sand mining) other species had encroached into their habitat. It is thus hypothesized that change in species diversity will lead to change in soil chemistry. In a 40 m × 90 m plot, diversity index (H) and importance value (Iv) of weed were estimated. Soil and weed samples were collected and analyzed for total hydrocarbon content (THC), Zinc (Zn), Lead (Pb) and Cadmium (Cd). All samples were analyzed with atomic absorption spectrophotometric method using the HACH DR 890 calorimeter (wavelength 420 nm). The result shows that swampy soils were more acidic (3.1 - 3.5) than sandy soils (4.2 - 4.7). Swampy soil was also more saline and thus has higher conductivity (8320 - 9880 μS/cm) than sandy soil (4320 - 5650 μS/cm). Mangrove swamp had higher total organic carbon (TOC) (2.25% - 3.41%) than sandy soil (0.12% - 0.21%). There was a significant difference in THC and heavy metals in soil (F8,63 = 2.04, P < 0.05), but there was no significant difference in THC and heavy metals in plant species (F8,63 = 247.0, P > 0.05). Concentration of THC and heavy metal was higher in plant than in soil. Reissantia indica, an aquatic weed, had the highest concentration of THC in root soil. A total of fifteen (15) weed species were identified, out of which Mariscus longibracteatus had the highest diversity (-0.366) followed by Mariscus ligularis (-0.339) and Paspalum vaginatum (-0.270). Similarly, M. longibracteatus had the highest importance value in the study site (Iv = 58.24). This result implies that the presence of weed species in mangrove forest is an indicator of human disturbance of the ecosystem. It also means that the weeds were bioaccumulating THC and heavy metals present in the soil.

Herbicidal Effects of Fungicides on Arable Weeds

In the present study, the herbicidal effects of two fungicides with the active ingredients expoxiconazole, fluxapyroxad, pyraclostrobin and fenpropimorph on the two arable weeds Lamium purpureum L. and Chenopodium album L. were investigated. The experiments were conducted in a climate chamber under defined conditions. Sowing pods were prepared and plants at the cotyledon leaf stage were pricked out in test pods. Fungicides were applied at six application rates: 0%, 12.5%, 25%, 50%, 100% and 200% of the maximum registered dose rate in Germany. Seven days after application, the first assessment was conducted, regarding growth stage, quantity of plants and visible plant damage. Fourteen days after application, the second and final assessment was conducted, regarding growth stage, quantity of plants, visible plant damage and the fresh weight of the plants. There were herbicidal effects of the fungicides, which were presumably due to the active ingredient epoxiconazole. Epoxiconazole has effects on enzymes that are dependent on cytochrome P-450 and inhibits sterol biosynthesis and probably gibberellin synthesis. By doing so, these fungicides have similar effects to plant growth regulators. Weed species showed differential sensitivities, contractions and growth inhibition and ED50-values were calculated. Notwithstanding the probably minor relevance of the present results in agricultural practice, some effects on arable weeds might result if fungicides are applied at an early growth stage in the field. In some cases, the crop-weed competition could be shifted to the benefit of the crop. Nevertheless, the results are interesting for the field of weed research and for the assessment of the ecotoxicology of fungicides.

Agroecological Influence on Rice Field Weeds in Anosibe Ifanja Commune(Middle West Madagascar)

Weeds, which cause loss of more than half of production, constitute one of obstacles to development of agriculturalproduction in Madagascar. This study aimed to characterize weed flora and to analyze constraint of weeding irrigated rice with aview to improve control strategy. A phytoecological study of weeds was carried out during 2018-2019 season, on 125 rice plots withan average area of 500 m², in Anosibe Ifanja, Middle-West region of Madagascar (18°52′ S and 46°50′ E). Surveys on croppingpractices and observations on rice field ecology and the importance of weed cover level were carried out in order to establishrelationship between factors affecting diversity, distribution and level of weed infestation in rice field. As a result, 47 weed speciesgrouped into about 20 families were identified. Weed cover quantification in each plot, permits to distinguish three major importancespecies, including Junglerice - Echinochloa colona (Poaceae), Tail - Leersia hexandra (Oryzoideae), saramollagrass - Ischaemumrugosum (Poaceae) and hemp sesbania - Sesbania rostrata (Fabaceae). Analysis of agro-ecological factors showed that all productiontechniques and growing conditions have a role to play in variability of plant cover level. Thus, the main production factors thatvegetation cover reduce state are ploughing to a depth of 30 cm, practice of ploughing off-season/in-season and good water control.Ecological factors, especially soil type, soil structure and topography, minimize weed cover in rice fields.

Nutrient Release during Residue Decomposition of Weeds Mown at Different Times in a Persimmon Orchard

Decomposition and nutrient release of the residue subsequent to mowing weeds remain poorly understood in persimmon orchards of South Korea. The litterbags including various weed residues were deposited on the soil surface under the tree canopy to simulate the fate of weeds mowed on 13 May, 13 July, and 13 September 2011 and 2012. Rate of decomposition and nutrient release of the residues depended on different mowing times. Residual dry mass (DM) of the 13 May weeds decreased by 17% - 21% of initial DM during 1 month and by 63% -71% until 2 months after litterbag deposition, and they?released 51% - 67% of nitrogen (N), 54% - 55% of phosphorus (P), and 92% - 94% of potassium (K) of respective initial amount until the first 2 months. The 13?July weeds rapidly decomposed during the first month, accounting for 51% - 64% of DM and released 49% - 67% of N, 27% - 54% of P, and 76% - 77% of K. When mowed on 13 September, the weed residue decomposed slower and?longer than the 13 May and 13 July weeds, losing 48% - 51% of DM, 36% - 39% of N, 60% - 64% of P, and 70% -77% of K during the first 2 months but continuing an active decomposition even at 6 months after the deposition. The results indicated that time of supplemental fertilization should be adjusted depending on mowing times, and the mowing times be controlled to meet seasonal demand of persimmon trees for nutrients.