Littérature scientifique sur le sujet « Constraining weeds »

This study was carried out among okra growers in the La M&eacute; region, with the aim of identifying farmers&rsquo; weed management practices and the main weeds present in the fields. Using a questionnaire coupled with a floristic inventory in each field, the agrotechnical characteristics of the farms and the main weed species were determined. The results show that 94.67% of the farmers surveyed use herbicides and 67.33% use insecticides. Almost all the herbicides used were total herbicides, applied before sowing. 68.67% of growers carry out three weed control operations per production cycle, and the weed control method most frequently used is chemical weed control combined with manual weed control. The inventory of major weeds reveals that 16 species are a constraint for the crop and 7 of them are cited with a high frequency. These were&nbsp;<em>Panicum maximum</em>,&nbsp;<em>Chromolaena odorata</em>,&nbsp;<em>Ageratum conyzoides</em>,&nbsp;<em>Mimosa pudica</em>,&nbsp;<em>Panicum laxum</em>,&nbsp;<em>Croton hirtus</em>&nbsp;and&nbsp;<em>Centrosema pubescens</em>. The floristic surveys showed that the constraining weeds come from four major botanical families: Asteraceae (37.5%), Poaceae (25%), Euphorbiaceae (18.75%) and Fabaceae (18.75%). Hemicryptophytes (41.84%) and Nanophanerophytes (34.05%) are the two biological types that contain the most constraining weeds. This study is a fundamental step towards initiating an effective weed management strategy for okra. The results of this study will make it possible to propose effective ways of controlling these weeds. These include reducing weeds to a tolerable nuisance threshold for the crop, setting up a trial to determine the critical weed period, and establishing crop rotations and combinations. published by the&nbsp;<strong> Journal of Biodiversity and Environmental Sciences (JBES)</strong>

Poor weed management can result in additional costs that can be estimated at over 35%. Determining of the most troublesome weeds is becoming an essential part of effective weed control. A study was therefore carried out in the south-east of Côte d'Ivoire, in plantain plantations, to identify abundant weeds and assess their potential for causing damage. Two approaches were used. The first one consisted in carrying out a survey of plantain growers and the second in carrying out floristic surveys in plantain fields. To do this, the degree of infestation and the Partial Harmfulness Index of the major weeds in these works were analysed. Growers have identified 19 weeds that are difficult to control. In terms of weed flora, 152 species divided into 115 genera belonging to 47 families were recorded. The infestation diagram distinguished 20 major weeds, of which Panicum laxum is the most aggressive (FC = 80.28%; ADaverage= 1.55). The Partial Harmfulness Index (PHI) determined five (5) potentially harmful weeds (PHI ≥ 1000). After cross-referencing the two lists of constraining and major weeds (survey and floristic survey), there is floristic homogeneity, with 25 constraining and major weeds in this study. With a view to better weed control in banana cultivation in the Mé region, growers should take into account the most abundant and constraining weeds in order to reduce yield losses.

The development of appropriate weed management strategies and efficient use of herbicides relies upon understanding weed-crop interactions. A field study was carried out to assess the effect of weed interference on leaves, internode and harvest index of dry bean (Phaseolus vulgaris L.). The experiment was established under a randomized complete block design with two types of weed interference treatments: plots with weeds and plots without weeds at different time intervals (0, 10, 20, 30, 40 and 50 days after crop emergence). The sigmoid Boltzmann model was used to quantify the crop traits as influenced by weed interference. Prolonged delays in weed removal reduced gradually the number of leaves of the crop. Weed interference decreased dry weight of leaves as well, so that the lowest value of it (33.49 g plant-1) was observed in full season during weed-infested treatment. Infestation of weeds affected the length of the crop internodes. While the weed interference duration increased, the length of the internodes decreased. Harvest index was also sensitive to weed competition. As the crop was kept weed-infested from the emergence for increasing periods of time, harvest index decreased to a value of 28.01%. A significant negative correlation between total biomass of weeds and dry bean traits (number of leaves, leaves dry weight, internode length and harvest index) was observed. Therefore, weeds are able to adversely affect dry bean growth through constraining environmental resources and impairing leaves as the photosynthetic areas.

Abstract Key message OrDeb2 confers post-attachment resistance to Orobanche cumana and is located in a 1.38 Mbp genomic interval containing a cluster of receptor-like kinase and receptor-like protein genes with nine high-confidence candidates. Abstract Sunflower broomrape is a holoparasitic angiosperm that parasitizes on sunflower roots, severely constraining crop yield. Breeding for resistance is the most effective method of control. OrDeb2 is a dominant resistance gene introgressed into cultivated sunflower from a wild-related species that confers resistance to highly virulent broomrape races. The objectives of this study were as follows: (i) locate OrDeb2 into the sunflower genome and determine putative candidate genes and (ii) characterize its underlying resistance mechanism. A segregating population from a cross between the sunflower resistant line DEB2, carrying OrDeb2, and a susceptible line was phenotyped for broomrape resistance in four experiments, including different environments and two broomrape races (FGV and GTK). This population was also densely genotyped with microsatellite and SNP markers, which allowed locating OrDeb2 within a 0.9 cM interval in the upper half of Chromosome 4. This interval corresponded to a 1.38 Mbp genomic region of the sunflower reference genome that contained a cluster of genes encoding LRR (leucine-rich repeat) receptor-like proteins lacking a cytoplasmic kinase domain and receptor-like kinases with one or two kinase domains and lacking an extracellular LRR region, which were valuable candidates for OrDeb2. Rhizotron and histological studies showed that OrDeb2 determines a post-attachment resistance response that blocks O. cumana development mainly at the cortex before the establishment of host-parasite vascular connections. This study will contribute to understand the interaction between crops and parasitic weeds, to establish durable breeding strategies based on genetic resistance and provide useful tools for marker-assisted selection and OrDeb2 map-based cloning.

Although in many countries of Sub-Sahara Africa, sweet potato has been found to be very important for food security for farmers who depended on it for their livelihood, little documentation on the production constraints, preferences for sweetpotato genotypes by farmers, pre- and post-harvest handling and value chain issues were available for North-Kivu province. Hence, a survey assessment was conducted (March-December 2021) in major sweetpotato growing territories in North-Kivu province. Data was collected through field visits, semistructured interviews, focus group discussions and field observations after structured questionnaire have been administered to farmers. Descriptive statistics were applied to analyze the data. The results indicated that sweetpotato is grown by rural households for food and cash, and women play a major role in cultivating the crop. The crop was cultivated on small plots, mainly in upland areas, during the rainy season and sometimes in valley bottoms during dry season. Most farmers provide their own planting materials or obtained vines free from neighbours. Vines were usually planted on mounds. Ridges were used in highland areas in lieu of mounds as a way to control soil erosion/land slide impacts. Sweetpotato is commonly solecropped, although it is occasionally intercropped with beans, maize, banana, and other crops. Key attributes for maintenance of varieties were access to healthy planting material availability and distribution, tolerance abiotic stresses, resistance to biotic stresses, good taste and high root yield , early maturity, cookability, low perishability during storage. Piecemeal harvesting was common except when larger quantities are harvested for sale. During the harvest period, people consume sweetpotatoes every day and sometimes for every meal. Peeling &amp; boiling or steaming is the most common method of preparation. Pests and diseases were reported to be associated with severe and high yield loss although incidence of pests and diseases were of high seasonal variations. The overall identified factors constraining productivity included shortage of land and planting materials, landrace low yield, some variety high sensitivity to weeds, diseases and insect pests aggressions, inaccessibility to financial credits. Post-harvest and value chain constraints included: high labour and transport costs, poor access to markets &amp; low market prices, inaccessibility to improved varieties, a lack of knowledge on processing and equipment, packaging, marketing and transportation problems, inadequate extension services and postharvest losses. Farmers indicated that flood and landslide/soil erosion were serious abiotic stresses. The result showed that age, education level of household head, land and household sizes, input costs, livestock ownership, access to market information and to financial credit or extension services, output and sales revenue may have a significant impact on outcome and affect household gross margin. Thus, enhancing farmers’ access to market information, boosting the production and productivity of the crop through better extension services and infrastructures, awareness creation on gender balanced market engagement and improvement in transportation facilities are the critical points that should get policy attentions in the study area. Results of this study can serve as a baseline reference for strategic breeding and other interventions to develop sweetpotato varieties according to the needs of the farmers.

Abstract How phenotypic and genetic divergence among populations is influenced by the genetic architecture of those traits, and how microevolutionary changes in turn affect the within-population patterns of genetic variation, are of major interest to evolutionary biology. Work on Ipomoea hederacea, an annual vine, has found genetic clines in the means of a suite of ecologically important traits, including flowering time, growth rate, seed mass, and corolla width. Here we investigate the genetic (co)variances of these clinally varying traits in two northern range-edge and two central populations of I. hederacea to evaluate the influence of the genetic architecture on divergence across the range. We find (1) limited evidence for clear differentiation between Northern and Southern populations in the structure of G, suggesting overall stability of G across the range despite mean trait divergence and (2) that the axes of greatest variation (gmax) were unaligned with the axis of greatest multivariate divergence. Together these results indicate the role of the quantitative genetic architecture in constraining evolutionary response and divergence among populations across the geographic range.

Irrigated agriculture requires high reliability from water delivery networks and high flows to satisfy demand at seasonal peak times. Aquatic vegetation in irrigation channels are a major impediment to this, constraining flow rates. This work investigates the use of remote sensing from unmanned aerial vehicles (UAVs) and satellite platforms to monitor and classify vegetation, with a view to using this data to implement targeted weed control strategies and assessing the effectiveness of these control strategies. The images are processed in Google Earth Engine (GEE), including co-registration, atmospheric correction, band statistic calculation, clustering and classification. A combination of unsupervised and supervised classification methods is used to allow semi-automatic training of a new classifier for each new image, improving robustness and efficiency. The accuracy of classification algorithms with various band combinations and spatial resolutions is investigated. With three classes (water, land and weed), good accuracy (typical validation kappa &gt;0.9) was achieved with classification and regression tree (CART) classifier; red, green, blue and near-infrared (RGBN) bands; and resolutions better than 1 m. A demonstration of using a time-series of UAV images over a number of irrigation channel stretches to monitor weed areas after application of mechanical and chemical control is given. The classification method is also applied to high-resolution satellite images, demonstrating scalability of developed techniques to detect weed areas across very large irrigation networks.

Low Transformation Temperature (LTT) alloys were developed in order to control the residual stress development by the martensitic phase transformation already during cooling of the weld metal. The positive effect of such LTT alloys on the mitigation of detrimental tensile residual stresses during welding has already been confirmed on the basis of individual laboratory tests. Within the current project it was experimentally investigated whether the phase transformation mechanisms are effective under increased restraint due to multi-pass welding of thicker specimens. The local residual stress depth distribution was analyzed non-destructively for V-type welds processed by arc welding using energy dispersive synchrotron X-ray diffraction (EDXRD). The use of high energy (20 keV to 150 keV) EDXRD allowed for the evaluation of diffraction spectra containing information of all contributing phases. As the investigated LTT alloy contains retained austenite after welding, this phase was also considered for stress analysis. The results show in particular how the constraining effect of increased thickness of the welded plates and additional deposited weld metal influences the level of the residual stresses in near weld surface areas. While the longitudinal residual stresses were reduced in general, in the transition zone from the weld to the heat-affected zone (HAZ) compressive residual stresses were found.

Organic farming can play an important role in rural development and food production, by reinforcing the trend toward sustainable agriculture and its purpose of ecosystem conservation. The agribusiness of organic farming is particularly relevant in family farming, given the labor availability and the short marketing circuits. The innovative techniques of organic farming, namely with soil fertility, weed and pest control, opens a wide range of possibilities in its development and extension. The expectation of organic farming profitability in small-scale family farming, supported by known successful examples, were the theme of a field study on Lis Valley Irrigation District to assess the constraints to its expansion in order to outline the procedures for the acquisition of technical knowledge, the adaptation of technologies, the support for the conversion of production models, and the specialized training of farmers for action. Results revealed that the: (i) farmer’s land structure, (ii) their mature age, (iii) low education level, and (iv) markets, are the main constrains for organic farming development. Furthermore, other uncertainties were identified, namely: (i) the certification process, (ii) the knowledge of new technologies, especially of crop protection, and (iii) the marketing problems to guaranteeing profitability. This study concludes that organic farming has significant potential for development in the Lis Valley and that the efforts and resources of the various stakeholders, namely the state, need to be harmonized to deliver effective support to farmers to promote organic farming that prioritizes: (i) rural development policies, (ii) supporting land restructuring, (iii) modernization of irrigation, (iv) stimulation of young farmers, (v) conversion and implementation of innovative technologies, (vi) the organization of farmers for better productive efficiency, and (vii) to facilitate market access.

Introduction. Paresis of hand has severe impact on the life of the stroke patients. Modified constrained induced movement therapy (mCIMT) can be used to treat the involved limb of the patient. It involves constraining of functional hand and increasing the activity of paretic hand which overcomes the “learned disuse” that develops following stroke but the constraining also creates difficulties for the patient and reduces his/her compliance to the treatment. Hence this trial aims to study the effect of mCIMT with and without interval to see if providing relaxation in between the treatment would be able to produce similar effect as mCIMT without interval protocol. Matgerial and methods. 44 patients were recruited in the study and were divided in to three groups: mCIMT without interval (n = 18), mCIMT with interval (n = 16) and control group (n = 10). Participants in three groups were examined for pain and functionality of hand through Patient rated wrist hand evaluation score and Box and Block test at pre and post intervention. The intervention was given for 6 days/week for two weeks. Therapy time was 2 hours and constrain was for 6 hours a day. Clinical trial registration number -CTRI/2019/12/022547. Results. No baseline differences were found in between the three groups. There was significant increase in box and block test score and significant decrease in PRWHE score in pre and post treatment readings for with and without interval mCIMT but non-significant changes in PRWHE score and box and block test were seen in control group. Conclusion. Both interval and without interval mCIMT was effective. Interval mCIMT was seen to be more comfortable than without interval mCIMT for the patient.

Simulations of building performance or HVAC systems performance usually cover a time period of several weeks, months or even a year. Therefore, the computational demand of simulation models of buildings or HVAC systems can be quite constraining for their practical application. A substantial simplification of the simulated problem is usually necessary to reduce the computational demand. The paper reports the development of a quasi 1D model of a thermally activated layer with phase change material. The model was developed in MATLAB and subsequently implemented as a TRNSYS type. The model was validated with data obtained from experiments with thermally activated panels. The experimental panels contained a 15 mm thick layer of gypsum plaster comprising 30 wt.% of microencapsulated phase change material. Plastic tubes for liquid heat carrier (water in the presented study) were embedded at the bottom of the plaster layer. Thermal imaging was used to acquire the average surface temperatures of the panels in the experimental investigations. The experimental and numerical results were in a good agreement.