Redhead, J.W.; Oliver, T.H.; Woodcock, B.A.; Pywell, R.F. (2020). Wheat yield resilience metrics for sample 10km x 10km grid cells in England, 2008-2017. NERC Environmental Information Data Centre. (Dataset). https://doi.org/10.5285/7dbcee0c-00ca-4fb2-93cf-90f2a5ca37ea
Data on resilience of wheat yields in England, derived from the annual Defra Cereals and Oilseeds production survey of commercial farms. The data presented here are summarised over a ten-year time-series (2008-2017) at 10km x10km grid cell (hectad) resolution. The data give the mean yield, relative yield, yield stability and resistance to an extreme event (the poor weather of 2012), for all hectads with at least one sampled farm holding in each year of the time-series (i.e. the minimum data required to calculate the resilience metrics). These metrics were calculated to explore the impact of landscape structure on yield resilience. The data also give the number of samples per year per hectad, so that sampling biases can be explored and filtering applied. No hectads are included that contain data from <9 holdings across the time series (the minimum level required by Defra to maintain anonymity is <5).
The data were created under the ASSIST (Achieving Sustainable Agricultural Systems) project by staff at the UK Centre for Ecology & Hydrology to enable exploration of the impacts of agriculture on the environment and vice versa, enabling farmers and policymakers to implement better, more sustainable agricultural practices.
Users of the data must include the following acknowledgement: Data has been derived from Defra Cereals and Oilseeds Production Survey by UKCEH with the explicit permission of the Department for the Environmental Food and Rural Affairs
Provenance & quality
The original yield data were collected by Defra using a survey of a stratified random sample of farm holdings, as part of the annual June census of the English agricultural industry. Data were available for 10 years (2008-2017), comprising average winter wheat yield per holding and coordinates locating each to 1km. UKCEH obtained these data under a confidentiality agreement with Defra. Data were cleaned to remove anomalous yield values (zero values, whole crop silage harvests and obvious outliers).
Because a new random sample of farm holdings is drawn each year, few had consecutive data across 10 years. To analyse yield variation over time and account for local spatial variation in farming practices data were therefore aggregated to mean annual yield per 10km x 10km Ordnance Survey grid cell (‘hectad’). This also preserves survey respondent anonymity by ensuring that no yield value can be attributed to the location of a single holding (a condition of use for the original Defra survey data, in line with the Agricultural Statistics Act 1979). Resilience metrics were then calculated across the time series (see below). Data included here give these metrics for 315 hectads with at least one sampled holding in each year of the time-series (i.e. the minimum data required to calculate the resilience metrics), although further analyses used only 137 that were deemed to be sufficiently well-sampled to avoid biases relating to sample size. This was based on thresholds for the minimum permissible number of samples per year and the number of years permitted to have this value, to determine which combination retained the maximum number of samples whilst removing the significant correlations between sample size and mean yield and between mean sample size and mean yield over time. A threshold value of no more than one year with a single sample and no more than two years having less than three samples was found to meet achieve this.
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