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1.
Ridolfia segetum is an umbelliferous weed frequent and abundant in sunflower crops in the Mediterranean basin. Field research was conducted to evaluate the potential of hyperspectral and multispectral reflectance and five vegetation indices in the visible to near infrared spectral range, for discriminating bare soil, sunflower and R. segetum at different phenological stages. This was a preliminary step for mapping R. segetum patches in sunflower using remote sensing for herbicide application decisions. Reflectance data were collected at three sampling dates (mid‐May, mid‐June and mid‐July, corresponding to vegetative‐early reproductive, flowering and senescent phenological stages respectively) using a handheld field spectroradiometer. Differences observed in hyperspectral reflectance curves were statistically significant within and between crop and weed phenological stages depending on sampling date, which facilitates their discrimination. Statistically significant differences in the multispectral and vegetation indices analysis showed that it is also possible to distinguish any of the classes studied. Our study provides some information for constructing the spectral libraries of sunflower and R. segetum in which the different phenological stages co‐existing in the field were considered. Hyperspectral and multispectral results suggest that mapping R. segetum patches in sunflower is feasible using airborne hyperspectral sensors, and high‐resolution satellite imagery or aerial photography, respectively, taking into account specific timeframes.  相似文献   

2.
Studies on competition between Ridolfia segetum Maris, and sunflower (Helianthemum annuus L.) were conducted at eight locations in southern Spain in 1990 and 1991. in order to define competition models and to estimate from these economic thresholds as affected by crop inputs and potential yields. Competition losses in sunflower crops ranged from 19% to 56% of weed–free yields. There were slightly better correlations between percentage sunflower reduction and weed density than with weed dry weight, (?0.66 and ?0.59, respectively). The weed competitive index, or sunflower crop dry weight reduction per unit dry weight of R. segetum, was 1.09. The percentage yield losses due to weed density (NPRt) were fitted to multiple linear, quadratic, exponential and hyperbolic models. The hyperbolic equation, %RSY=100 (1+1/b*NPRt)?1, where b=0.14 and is the R. segetum competitive ability index, had the lowest error sum of squares (SSE), and gave the best biological explanation for the competition response. Early emergence (before mid–March) made weeds about 1.5 times more competitive than late emergence. The economic threshold to offset the cost of a shallow post–emergence tillage, assuming 70% control efficiency, ranged from about 2.5 plants m ?2 for low–yielding crops(1200kgha?1) to less than one plant m?2 for higher–yielding crops (2800 kg ha?1).  相似文献   

3.
Weeds and weed control are major production costs in global agriculture, with increasing challenges associated with herbicide‐based management because of concerns with chemical residue and herbicide resistance. Non‐chemical weed management may address these challenges but requires the ability to differentiate weeds from crops. Harvest is an ideal opportunity for the differentiation of weeds that grow taller than the crop, however, the ability to differentiate late‐season weeds from the crop is unknown. Weed mapping enables farmers to locate weed patches, evaluate the success of previous weed management strategies, and assist with planning for future herbicide applications. The aim of this study was to determine whether weed patches could be differentiated from the crop plants, based on height differences. Field surveys were carried out before crop harvest in 2018 and 2019, where a total of 86 and 105 weedy patches were manually assessed respectively. The results of this study demonstrated that across the 191 assessed weedy patches, in 97% of patches with Avena fatua (wild oat) plants, 86% with Raphanus raphanistrum (wild radish) plants and 92% with Sonchus oleraceus L. (sow thistles) plants it was possible to distinguish the weeds taller than the 95% of the crop plants. Future work should be dedicated to the assessment of the ability of remote sensing methods such as Light Detection and Ranging to detect and map late‐season weed species based on the results from this study on crop and weed height differences.  相似文献   

4.
Mapping weed densities within crops has conventionally been achieved either by detailed ecological monitoring or by field walking, both of which are time‐consuming and expensive. Recent advances have resulted in increased interest in using Unmanned Aerial Systems (UAS ) to map fields, aiming to reduce labour costs and increase the spatial extent of coverage. However, adoption of this technology ideally requires that mapping can be undertaken automatically and without the need for extensive ground‐truthing. This approach has not been validated at large scale using UAS ‐derived imagery in combination with extensive ground‐truth data. We tested the capability of UAS for mapping a grass weed, Alopecurus myosuroides , in wheat crops. We addressed two questions: (i) can imagery accurately measure densities of weeds within fields and (ii) can aerial imagery of a field be used to estimate the densities of weeds based on statistical models developed in other locations? We recorded aerial imagery from 26 fields using a UAS . Images were generated using both RGB and Rmod (Rmod 670–750 nm) spectral bands. Ground‐truth data on weed densities were collected simultaneously with the aerial imagery. We combined these data to produce statistical models that (i) correlated ground‐truth weed densities with image intensity and (ii) forecast weed densities in other fields. We show that weed densities correlated with image intensity, particularly Rmod image data. However, results were mixed in terms of out of sample prediction from field‐to‐field. We highlight the difficulties with transferring models and we discuss the challenges for automated weed mapping using UAS technology.  相似文献   

5.
The economic benefits of using site‐specific weed management (SSWM) are related to the proportion of the field that is weed‐infested, the number of weed patches and the spatial resolution of sampling and spraying technologies. In this paper we simulate different combinations of these factors using parameter values obtained for Avena sterilis ssp. ludoviciana growing in Spanish winter barley crops. The profitability of SSWM systems increased as the proportion of the field infested by this weed decreased and when patch distribution was more concentrated. Under most of the conditions tested, positive net returns for SSWM were obtained when the weed‐infested area was smaller than 30%. The highest net return occurred using a 12 m × 12 m mapping and spraying resolution. The critical parameter that determined the economic viability of patch mapping and spraying resolution was the technology costs. The site specific strategy was economically superior to the standard strategy (overall herbicide application) in most cases. However, the differential between the two strategies decreased when the number of patches and the resolution of mapping and spraying increased, such that the highest net returns were obtained with a single patch covering 14% of the field and using a 12‐m mapping and spraying resolution; whereas the worst net returns were obtained for all patch numbers when 64% of the field was infested and a 3‐m mapping and spraying resolution was used.  相似文献   

6.
A sugarbeet field experiment was conducted in 1999 and 2000 to measure beet yield where Sinapis arvensis or Lolium perenne were growing in the crop row at 2, 4 or 8 cm from the beet plants. The weeds were removed by cutting once in the growing season in either late May, mid‐June or early July. The number of neighbouring beet plants to every target beet plant was recorded. Projected leaf cover of a subset of the data with non‐cut weeds was analysed by using image analysis to investigate whether this could be used to predict beet yield loss early in the growing season. Increasing the distance between beet and weed from 2 to 8 cm increased the beet yield significantly by an average of 20%, regardless of weed species. The dry weight of non‐cut and re‐growing weeds at harvest time decreased when cutting was postponed to the period between mid‐June and early July. The number of neighbours described a sigmoidal yield decline of the single beet plants. Results from image analysis showed that approximately 33 g of beet yield was lost in October/November for each per cent relative projected leaf cover of the weeds in May, despite variation in growing conditions. The results are discussed in relation to potentials for robotic in‐row weed control.  相似文献   

7.
The influence of weather and agronomic factors on the activity of six selective herbicides applied at reproductive stages of development for the reduction in seed production of Raphanus raphanistrum in wheat was evaluated. The herbicides used in this way generally reduced seed production by between 80% and 100%. Triasulfuron and mixtures of triasulfuron + MCPA consistently provided the greatest reduction in seed production. This was greater when herbicides were applied at the bud and early flowering stages of R. raphanistrum and the efficacy of the herbicides increased as maximum temperature on the day of spraying increased over the range 14–24°C. An applied model developed from these results predicts the reduction in seed production of R. raphanistrum, for each herbicide, given the stage of weed development and maximum temperature on the day of its application. Wheat yield was significantly reduced as densities of R. raphanistrum increased, with predicted losses at low densities being approximately half of those reported in the literature. There was no consistent evidence that the late application of herbicides had any negative effect on wheat yield through crop injury, nor was there any indication of yield improvement. It is concluded that certain herbicides applied during the reproductive phase of development have considerable potential to reduce R. raphanistrum seed production in wheat crops. As part of an integrated strategy, such late post‐emergence application of selective herbicides to regulate seed production has a likely role for managing weed seedbanks, but little or no value for counteracting weed competition.  相似文献   

8.
The effects of cover crops on weeds and the underlying mechanisms of competition, physical control and allelopathy are not fully understood. Current knowledge reveals great potential for using cover crops as a preventive method in integrated weed management. Cover crops are able to suppress 70–95% of weeds and volunteer crops in the fall‐to‐spring period between two main crops. In addition, cover crop residues can reduce weed emergence during early development of the following cash crop by presenting a physical barrier and releasing allelopathic compounds into the soil solution. Therefore, cover crops can partly replace the weed suppressive function of stubble‐tillage operations and non‐selective chemical weed control in the fall‐to‐spring season. This review describes methods to quantify the competitive and allelopathic effects of cover crops. Insight obtained through such analysis is useful for mixing competitive and allelopathic cover crop species with maximal total weed suppression ability. It seems that cover crops produce and release more allelochemicals when plants are exposed to stress or physical damage. Avena strigose, for example, showed stronger weed suppression under dry conditions than during a moist autumn. These findings raise the question of whether allelopathy can be induced artificially. © 2019 Society of Chemical Industry  相似文献   

9.
Weed seed predation is an ecosystem service, influencing weed population dynamics. The impact of weed seed predation on weed population dynamics depends on how predators respond to seed patches at the field scale. Seed predation will be most effective if the proportion of seeds predated increases with increasing size and seed density of patches. Density‐dependent rodent seed predation was measured by varying seed density and patch size in four irrigated conventionally managed cereal fields in north eastern Spain. Artificial weed seed patches were created by applying a range of Lolium multiflorum seed densities from 0 to 7500 seeds m?2 in 225 m2 patches (2008) or in patches that varied in size from 1 to 9 m2 (2009). Seed predation was estimated using seed cards and seed frames. The granivorous rodents Mus spretus and Apodemus sylvaticus caused high seed predation rates (92%) in three fields, whereas in a fourth field, it was lower (47%). Rodents responded in an inversely density‐dependent manner, but this had little biological meaning as even in patches seeded with the highest density, the input to the soil seedbank was reduced by 88%. For the period of time this experiment lasted, hardly any new seeds would have entered the seedbank.  相似文献   

10.
Parietaria debilis is a dominant annual weed in many non‐tillage fallow and undisturbed areas in Argentina. Herbicides control P. debilis inconsistently. A study on the growth of P. debilis, in a fallow in a soyabean–maize rotation including glyphosate‐resistant cultivars and in an undisturbed area without crops or weed control, was conducted in the central soyabean area of Argentina. The biomass dynamics of all species in the community, as well as biomass, density and growth traits of P. debilis were assessed. Biomass of several species including P. debilis and total biomass were greater in undisturbed than in fallow plots in both years of the study. Diversity was greater in undisturbed plots in 2000, but no differences in diversity were observed in 2001. In both treatments, P. debilis emergence began in March and finished in October and density increased from March to May. High mortality occurred in June and July, particularly in undisturbed plots. In the fallow plots, no other tall weed species were present and light interception was higher in spring when fruit production was at its peak. Conversely, in the undisturbed plots, P. debilis was substantially taller and had greater leaf area due to lower light interception by the high canopy of the rest of the community. In fallow, P. debilis is favoured by single applications of glyphosate, because the herbicide eliminates competitors. Control, if applied, should be directed to both fallow and undisturbed environments, as the weed produces considerable numbers of seeds and can invade extensively managed areas.  相似文献   

11.

BACKGROUND

Ecballium elaterium (common name: squirting cucumber) is an emerging weed problem in hedgerow or superintensive olive groves under no tillage. It colonizes the inter-row area infesting the natural or sown cover crops, and is considered a hard-to-control weed. Research in other woody crops has shown E. elaterium has a patchy distribution, which makes this weed susceptible to design a site-specific control strategy only addressed to E. elaterium patches. Therefore, the aim of this work was to develop a methodology based on the analysis of imagery acquired with an uncrewed aerial vehicle (UAV) to detect and map E. elaterium infestations in hedgerow olive orchards.

RESULTS

The study was conducted in two superintensive olive orchards, and the images were taken using a UAV equipped with an RGB sensor. Flights were conducted on two dates: in May, when there were various weeds infesting the orchard, and in September, when E. elaterium was the only infesting weed. UAV-orthomosaics in the first scenario were classified using random forest models, and the orthomosaics from September with E. elaterium as the only weed, were analyzed using an unsupervised algorithm. In both cases, the overall accuracies were over 0.85, and the producer's accuracies for E. elaterium ranged between 0.74 and 1.00.

CONCLUSION

These results allow the design of a site-specific and efficient herbicide control protocol which would represent a step forward in sustainable weed management. The development of these algorithms in free and open-source software fosters their application in small and medium farms. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   

12.
The goal of this study was to identify factors determining weed species composition in soyabean crops in Hungary, where its expanding production faces difficult weed problems. The abundance of weed flora was measured in 262 fields across the country, along with 38 background variables. Using a minimal adequate model containing 24 terms with significant net effects, 21.6% of the total variation in weed species data could be explained. Plot location (edge vs core position, the single site variable in our analysis) was found to be the most important explanatory variable that was followed by a set of environmental (temperature, precipitation, altitude, soil texture, pH, Ca, K, Na and humus content), cultural (cultivar maturity, organic manure, fertiliser P and N, row spacing) and weed management (flumioxazin, pendimethalin, dimethenamid, propaquizafop, bentazone, quizalofop‐p‐ethyl, quizalofop‐p‐tefuril, linuron, thifensulfuron) factors. Variation partitioning revealed that environmental variables accounted for about four times more variance than cultural and about two and half times more than weed management variables. Chenopodium album, Ambrosia artemisiifolia, Hibiscus trionum, Echinochloa crus‐galli and Convolvulus arvensis were the most dominant and frequent weeds, but their abundance was influenced by different factors. The responses of weed species to the studied variables provide new information about their ecological behaviour, and our findings also can be used to develop better weed management strategies.  相似文献   

13.
Increased demand for pesticide-free food and the development of herbicide-resistant weed populations have created a need for non-chemical weed-control tools. A candidate mechanical tool for controlling weeds in the seeding line (intra-row zone) is the finger weeder. This study thus aimed to evaluate the safety and weed-control efficacy of the finger weeder in various irrigated field crops. Eight field trials were conducted in processing tomato, sweet corn, sunflower, cotton, and beetroot over 2 years. The finger weeder treatments were applied as the sole weed-control method (single or double treatments) and in combination with herbicides. A mini meta-analysis was used to evaluate the overall effect of the finger weeder treatments on crop stand and yield and on weed control efficacy. Weed density in the control not treated with herbicides nor a finger weeder ranged between 2 and 62 weeds m−2. The finger weeder treatments resulted in a significant reduction in weed density, which ranged between 40% and 90%. The weed density following the double finger weeder treatment was not significantly different from that for the conventional herbicide-based treatment (p = 0.32) and could therefore be considered as an effective environmentally friendly alternative. Furthermore, a single FW treatment integrated with herbicide application gave better weed control than the conventional herbicide treatment (p = 0.04). This treatment was safe for the crops with no significant stand (p = 0.19) or yield (p = 0.29) reductions compared to commercial treatment. The results of this study demonstrate the promise of the finger weeder as an effective tool within integrated weed management systems for conventional agro-systems. The tool offers a rational weed-control solution for sustainable systems under irrigation.  相似文献   

14.
Long‐term experiments were conducted in two winter barley fields in central Spain to determine the spatial stability of Avena sterilis ssp. ludoviciana populations under annual applications of low rates of imazamethabenz herbicide. Weed density was sampled every year (over 5 years in the first field and over 3 years in the second) on the same grid locations prior to herbicide application. Although weed patches were stable in their location, weed density decreased in most of the years. In the first field, the populations decreased exponentially over the 5‐year period. The rates of population decline were dependent on the initial density of the population, being higher for the central core of the patches and lower for the low‐density areas. Under the conditions present in this experiment, it was possible to reduce heavy weed patches (up to 1200 seedlings m?2) down to relatively safe levels (18 seedlings m?2) in a period of 3 years using a density‐specific control programme, applying low rates of herbicides when weed densities were below a given level (1000 seedlings m?2). However, under adverse environmental conditions, half rates of the herbicide failed to control the weed populations adequately. The stability of the location of patches of A. sterilis ssp. ludoviciana suggest that weed seedling distributions mapped in one year are good predictors of future seedling distributions. However, the actual densities established each year will depend on the control level achieved the previous year and the climatic conditions present during the establishment period.  相似文献   

15.
Through a detailed case study of a two‐species (Lolium rigidum and Avena sterilis) weed community at contrasting scales, this paper examined factors that affect weed distribution across space and time in a commercial wheat field in north‐east Spain. A. sterilis showed relatively stable spatial distribution and spatial structure of its population over time at large scale, with well‐defined patches, although weed density rose quickly. L. rigidum showed poorly defined patches that were not stable across time. Interaction between species could explain to some degree the spatial distribution at large scale: a negative relationship was detected between the spatial structures of both weed populations. At fine scale, both species showed a clear interaction effect from primary dispersal (more important in A. sterilis) and secondary dispersal from combine harvesting (more important in L. rigidum).  相似文献   

16.
Approaches to the biological control of weeds in arable crops and integration of biological weed control with other methods of weed management are broadly discussed. Various types of integrative approaches to biological control of weeds in crops have been studied within the framework of a concerted European Research Programme (COST‐816). During the period 1994–99, some 25 institutions from 16 countries have concentrated on five target weed complexes. Some major scientific achievements of COST‐816 are: (i) combination of the pathogen Ascochyta caulina with an isolated phytotoxin produced by this fungus to control Chenopodium album in maize and sugar beet; (ii) the elaboration and preliminary field application of a system management approach using the weed:pathogen system Senecio vulgaris:Puccinia lagenophorae to reduce the competitiveness of the weed by inducing and stimulating a disease epidemic; (iii) combination of underseeded green cover with the application of spores of Stagonospora convolvuli to control Convolvulus species in maize; (iv) assessment of the response of different provenances of Amaranthus spp. to infection by Alternaria alternata and Trematophoma lignicola, the development of formulation and delivery techniques and a field survey of native insect species to control Amaranthus spp. in sugar beet and maize; (v) isolation of strains of different Fusarium spp. that infect all the economically important Orobanche spp. and development of novel, storable formulations using mycelia from liquid culture. Although no practical control has yet been reached for any of the five target weeds, potential solutions have been clearly identified. Two major routes may be followed in future work. The first is a technological approach focusing on a single, highly destructive disease cycle of the control agent and optimizing the efficacy and specificity of the agent. The second is an ecological approach based on a better understanding of the interactions among the crop, the weed, the natural antagonist and the environment, which must be managed in order to maximize the spread and impact of an indigenous antagonist on the weed.  相似文献   

17.
As herbicides have limited effect in controlling Bromus diandrus in no‐till dryland cereal fields, the integration of chemical and cultural methods needs to be investigated. A field study was carried out in Lleida (Spain) during 2008–09, 2009–10 and 2010–11 seasons, in a no‐till winter cereal field integrating delayed crop sowing with herbicides in a barley–wheat–wheat rotation. Three crop sowing dates were considered: D1, mid‐October; D2, mid‐November; and D3, early December, and the herbicides mesosulfuron‐methyl plus iodosulfuron‐methyl‐sodium were applied in wheat. Weed density, cumulative emergence and fecundity were estimated for each sowing date. In all three seasons, a significant reduction in the cumulative emergence of B. diandrus as compared to D1 was observed in D2 (82.0, 97.5 and 98.1%) and D3 (80.8, 98.7 and 97.2%). In addition, a significant decrease in weed density and seed rain was observed across all sowing dates and seasons. The herbicide used in wheat was more effective under delayed sowing, due to lower weed density and presence of less developed weed seedlings. After three seasons, the populations of B. diandrus were completely depleted in D2 and D3. This study demonstrates the possibility of eliminating brome infestations in dryland cereal fields in no‐till systems through the integration of cultural and chemical strategies.  相似文献   

18.
Solanum elaeagnifolium (silverleaf nightshade) is an invasive perennial weed in Australia, with aerial growth commencing in spring from either the perennial root system or the soil seedbank, with senescence occurring in autumn. A total of 642 S. elaeagnifolium individuals were collected at flowering from 92 locations in south‐eastern Australia to study morphological variation and its implications for management. Large morphological variation was found between individuals from different locations. Leaf length, width and area ranged from 1.44 to 10.6 cm, 0.39 to 4.09 cm and 0.41 to 25.8 cm2 respectively. Plants from higher rainfall regions were significantly taller and had larger leaves, suggesting a possible correlation between rainfall and morphology. Scanning electron microscopy comparison of leaf surfaces showed lower trichome and stomatal densities on the adaxial surface (67.0 ± 3.3 trichomes mm?2 and 603.4 ± 29.2 stomata mm?2 respectively) than on the abaxial surface (131.9 ± 7.2 trichomes mm?2 and 813.7 ± 30.5 stomata mm?2 respectively). The morphological plasticity of S. elaeagnifolium highlighted in this study could probably contribute to its adaptability and partly explain its establishment and continuing expansion in Australia.  相似文献   

19.
An arable field was subdivided and subjected to either deep inversion ploughing or non‐inversion cultivation after viable seeds of Bromus sterilis had been sown into oilseed rape stubble. After sowing in isolated plots distributed within the field, sequences of cropping treatments for the establishment of two successive winter wheat crops were applied. Each subfield was split into an uphill and a downhill direction for soil cultivation. The field had a 10° slope. In the season following seed introduction, 2.6% of the introduced seeds had successfully germinated and established in the non‐inversion cultivation regime, when no effective graminicide was applied. Ploughing eradicated B. sterilis. Using differential global positioning system (DGPS) mapping of the whole field population, emerged plants were observed up to 8.7 m (uphill treatment) and 21.3 m (downhill treatment) of their initial source. The median distance seeds were transported was 2.3 m uphill and 4.8 m downhill. Post‐emergence application of the herbicide propoxycarbazone slightly reduced weed density and seed weight, and almost halved weed seed production. Application of fenoxaprop‐P‐ethyl was followed by higher density of plants, tillers and seeds of B. sterilis. Seed viability was unaffected by herbicide use. Thus, in the second wheat crop following seed rain, the weed population was dispersed more widely in the field, such that 20–30% of seeds were dispersed more than 5 m distance from the first year's foci of infestation. The relevance of soil cultivation to secondary dispersal of B. sterilis is discussed.  相似文献   

20.
Weed competition and nutrient scarcity often restrict organic cereal production, especially where the availability of livestock manure is limited. While harrowing of annual weeds and legume cover crops can be used, these methods are both executed in early spring and may hinder each other. Two cycles of a 2‐year crop rotation were carried out in south‐east Norway (60°42′N, 10°51′E, altitude 250 m) with weed harrowing and undersown cover crops (WHCC) at two fertiliser rates (40 and 100 kg nitrogen ha?1). The effect of the WHCC treatments was measured by weed density and species, weed biomass, changes in weed seedbank and grain yield. The weed density depended on the interaction between WHCC, fertiliser and year. On average, pre‐emergence weed harrowing reduced weed density by 32% and weed biomass by 49%, while pre‐ and post‐emergence weed harrowing reduced weed density by 59% and weed biomass by 67% compared with the untreated control. Spergula arvensis became more abundant at low rather than at high fertiliser rates. On average, white clover cover crop sown after pre‐emergence weed harrowing resulted in the highest yields for both oat (+12.1%) and wheat (+16.4%) compared with the untreated control. Despite differences in weed population density and biomass among WHCC treatments within years, the weed biomass, weed density and seedbank increased for all WHCC treatments over the 4‐year period. More research is required into improving the efficacy of mechanical and cultural weed suppression methods that organic systems rely on.  相似文献   

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