- United Kingdom
Helen Metcalfe
Rothamsted Research, Net Zero and Resilient Farming, Faculty Member
- University of Reading, Agriculture, Graduate Studentadd
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The expansion of irrigated agriculture and recurrent drought periods poses a serious threat to the renewability and sustainability of common water resources in arid and semi-arid regions. These shared resources can take the form of dam... more
The expansion of irrigated agriculture and recurrent drought periods poses a serious threat to the renewability and sustainability of common water resources in arid and semi-arid regions. These shared resources can take the form of dam water which is shared between farmers according to a predefined schedule or groundwater which the farmers independently extract. The dam water is less expensive to use but this source can be limited in drought years risking crop productivity. Groundwater is a more reliable resource but is more expensive to extract and can cause soil salinity. Simulating agricultural management systems requires understanding and quantifying how biophysical and socio-economical constraints influence the decisions of farmers. Therefore, this research aimed to develop an agent-based modelling (ABM) approach to simulate farmer behaviour in irrigation management. The Theory of Planned Behaviour was used as a theoretical framework to simulate decision models that were integr...
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Research Interests: Weed Control and Weed
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Policy makes and other stakeholders working to improve the sustainability of agriculture need access to information on soil spatial variation, and the impacts of management strategies that policy might promote. Models and data can provide... more
Policy makes and other stakeholders working to improve the sustainability of agriculture need access to information on soil spatial variation, and the impacts of management strategies that policy might promote. Models and data can provide such information but typically such products are developed in isolation and so do not allow for an integrated trade-off analysis. To overcome this limitation, we have developed a GIS- modelling framework (GIS-MF) that allows users to interrogate integrated models and data layers. This GIS-MF prototype has been developed for the Tensift watershed which is in the region of Marakesh-Safi, Morocco. The alpha version of the software contains four main components: (i) a field to watershed-scale Digital Soil Mapping viewer, (ii) a watershed scale Ecosystems Services Report viewer (iii) an Interactive Ecosystem Service and Environmental Impacts viewer that allows trade-offs to be explored and (iv) a field-scale yield prediction tool. For each component it...
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A crop sequence generator for the UK as described by Sharp et al. 2021 (under review).
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Concerns around herbicide resistance, human risk, and the environmental impacts of current weed control strategies have led to an increasing demand for alternative weed management methods. Many new weed management strategies are under... more
Concerns around herbicide resistance, human risk, and the environmental impacts of current weed control strategies have led to an increasing demand for alternative weed management methods. Many new weed management strategies are under development; however, the poor availability of accurate weed maps, and a lack of confidence in the outcomes of alternative weed management strategies, has hindered their adoption. Developments in field sampling and processing, combined with spatial modelling, can support the implementation and assessment of new and more integrated weed management strategies. Our review focuses on the biological and mathematical aspects of assembling within-field weed models. We describe both static and spatio-temporal models of within-field weed distributions (including both cellular automata (CA) and non-CA models), discussing issues surrounding the spatial processes of weed dispersal and competition and the environmental and anthropogenic processes that affect weed s...
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Weed population dynamics models are an important tool for predicting the outcome of alternative Integrated Weed Management (IWM) scenarios. The growing problem of herbicide resistance has increased the urgency for these tools in the... more
Weed population dynamics models are an important tool for predicting the outcome of alternative Integrated Weed Management (IWM) scenarios. The growing problem of herbicide resistance has increased the urgency for these tools in the design of sustainable IWM solutions. We developed a conceptual framework for defining IWM as a standardised input template to allow output from different models to be compared and to design IWM scenarios. The framework could also be used as a quantitative metric to determine whether more diverse systems are more sustainable and less vulnerable to herbicide resistance using empirical data. Using the logic of object-oriented programming, we defined four classes of weed management options based on the stage in the weed life cycle that they impact and processes that mediate their effects. Objects in the same class share a common set of properties that determine their behaviour in weed population dynamics models. Any weed control “event” in a system is associ...
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A crop sequence generator for the UK as described by Sharp et al. 2021 (under review).
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A shiny app exploring some principles of ecological modelling. The app is hosted at https://hmetcalfe1.shinyapps.io/BGmodel/ The app uses a real-world example of a problematic agricultural weed and how we might model its growth year on... more
A shiny app exploring some principles of ecological modelling. The app is hosted at https://hmetcalfe1.shinyapps.io/BGmodel/ The app uses a real-world example of a problematic agricultural weed and how we might model its growth year on year. The data used in the examples are simulated data and are not derived from experiments. The app is aimed at 16-18 year-olds interested in pursuing a career in applied mathematics and can be used as a stand alone tool or as a teaching aid in a classroom setting.
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A crop sequence generator for the UK as described by Sharp et al 2020 (under review)
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Alopecurus myosuroides Huds. (black-grass) grows in patches within fields. This presents an opportunity for site-specific management by patch spraying. Despite the economic and environmental benefits of this type of management, it is not... more
Alopecurus myosuroides Huds. (black-grass) grows in patches within fields. This presents an opportunity for site-specific management by patch spraying. Despite the economic and environmental benefits of this type of management, it is not being readily taken up by farmers, largely due to the risk of missing weeds that fall outside of established patches. I focus on the environmental determinants of patch location in A. myosuroides and the scale-dependence of relationships between A. myosuroides and environmental properties. Understanding these relationships allowed me to determine which abiotic factors can be used to identify A. myosuroides vulnerable zones within fields and if these relationships occur at scales appropriate for management. This presents a more conservative approach than patch spraying according to observations of previous years’ infestations, as a greater area of the field is sprayed, yet the overall use of pesticide is still reduced. By combining field work, pot ex...
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Sustainable strategies for managing weeds are critical to meeting agriculture’s potential to feed the world’s population while conserving the ecosystems and biodiversity on which we depend. The dominant paradigm of weed management in... more
Sustainable strategies for managing weeds are critical to meeting agriculture’s potential to feed the world’s population while conserving the ecosystems and biodiversity on which we depend. The dominant paradigm of weed management in developed countries is currently founded on the two principal tools of herbicides and tillage to remove weeds. However, evidence of negative environmental impacts from both tools is growing, and herbicide resistance is increasingly prevalent. These challenges emerge from a lack of attention to how weeds interact with and are regulated by the agroecosystem as a whole. Novel technological tools proposed for weed control, such as new herbicides, gene editing, and seed destructors, do not address these systemic challenges and thus are unlikely to provide truly sustainable solutions. Combining multiple tools and techniques in an Integrated Weed Management strategy is a step forward, but many integrated strategies still remain overly reliant on too few tools....
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The efficacy of pre-emergence herbicides within fields is spatially variable as a consequence of soil heterogeneity. We quantified the effect of soil organic matter on the efficacy of two pre-emergence herbicides, flufenacet and... more
The efficacy of pre-emergence herbicides within fields is spatially variable as a consequence of soil heterogeneity. We quantified the effect of soil organic matter on the efficacy of two pre-emergence herbicides, flufenacet and pendimethalin, against Alopecurus myosuroides and investigated the implications of variation in organic matter for weed management using a crop-weed competition model. Soil organic matter played a critical role in determining the level of control achieved. The high organic matter soil had more surviving weeds with higher biomass than the low organic matter soil. In the absence of competition, surviving plants recovered to produce the same amount of seed as if no herbicide had been applied. The competition model predicted that weeds surviving pre-emergence herbicides could compensate for sublethal effects even when competing with the crop. The ED50 (median effective dose) was higher for weed seed production than seedling mortality or biomass. This difference ...
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There is a continuing trend toward development of baked products with a healthy nutritional profile. However, to succeed in the market, it is essential that sensory properties of baked products not be compromised. Texture is an important... more
There is a continuing trend toward development of baked products with a healthy nutritional profile. However, to succeed in the market, it is essential that sensory properties of baked products not be compromised. Texture is an important aspect of this. Instrumental measurements are important tools for product developers that can complement sensory panel assessments and enable quantification of the effects of process variations. A range of testing protocols and instruments suitable for different product types is available. Compression between flat plates is appropriate for testing compressible products such as breads and cakes: initial loading provides information on firmness, and subsequent unloading and recompression measure properties such as cohesiveness. Examples are presented from trials evaluating salt content and bran supplementation in bread and for a gluten-free cake development project. Brittle products such as biscuits (cookies and crackers) can be tested using protocols such as three point be...