README
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Dataset title:
Data for: Determinants of yield variation of organic cereals in productive agricultural areas

Creators:
Rafaelle Reumaux, Melanie Karlsson, Romain Carrié, Ingrid Öborn, Christine A Watson, Göran Bergkvist, A Sigrun Dahlin, Johan Ekroos, Johanna Wetterlind, Henrik G Smith

Responsible organization:
Lund University

See the Researchdata.se catalogue entry for this dataset for complete metadata, including the dataset description, recommended citation, contact information, and information about how to obtain the dataset. 

Description: This dataset contains data on yield, crop management, field measurements and field conditions for organic spring barley and winter wheat fields in agricultural areas of southern Sweden from 2020 (81 fields in total). Collected to determine yield limitations for these two crops and the relative importance and relationships between management (for example fertilisation, weeding, soil cultivation, preceding crop, crop rotation, time since conversion to organic farming) and its effects on various measurement of the field state (for example nutrient levels, weed, diseases) as well as soil characteristics and weather.

License: CC0



Essential information for dataset reuse.
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56 farms were found that were organically certified, willing to let us visit their fields, grew spring barley or winter wheat in 2020 and located within the regions of Skåne, Halland and Västergötland. One typical field per farm and crop was visited. Data was gathered in four 2x2 meter observation plots in each field, placed to represent the variation in soil clay content across the field, and the data are averages across these four plots. Field visits measured plant nitrogen levels (through SPAD) early in the cropping season (late May to early June), weeds, pests and diseases measured during peak growing season (late June to early July), and soil samples gathered shortly before harvest and then air dried to analyse phosphorus and potassium levels (ammonium acetate-lactate method), as well as pH and soil organic matter content (loss on ignition). 

After this the farmers were contacted to get information about the fields management operations and yield. This included when the field was converted to organic management, what the aim of the crop was, sowing date and density, ploughing, soil cultivation methods and frequency, weed control methods and frequency, type and amount of fertiliser application, preceding crop and crop rotation.

Additional contextual data was gathered from land-use (Nationell marktäckedata; Swedish Environmental Protection Agency, 2018), weather (Copernicus E-OBS; Cornes et al., 2018) and soil maps (Digitala åkermarkskartan; Piikki & Söderström, 2019), averaged for the entire field and/or summed over time.

Included in the dataset is both the original data and also values that have been regionally group mean centered, as used in the related publication. The data is split between spring barley (SB) and winter wheat (WW) and each row represents one field, 52 fields with spring barley and 29 with winter wheat. 



Datafile description for "OriginalData_noncentered_XX.csv" for spring barley (SB) and winter wheat (WW)
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Contains all the original data values for the two crops, of all data types and sources:
-StudyArea: which of the two study areas the field was in, northernArea=Västergötland, southernArea=Skåne or Halland
FIELD YIELD AND MANAGEMENT DATA:
-HusbandryAtFarm: if the farm had animal husbandry or not
-Yield_kgha: crop yield for the whole field as given by the farmer, in kg/ha 
-YearOfTransition: the year that the field was converted to organic management
-PlannedUseCrop: the farmers planned or intended use of the crop at the time of sowing it
-SowingDate_dayofyear: the time of sowing the crop, given in the day number from 1 jan in 2019 for winter wheat and 1 jan 2020 for spring barley, average is used if a range was given by the farmer
-SowingDensity_kgha: The sowing rate (density) reported by the farmer, in kg/ha
-SeedHeatTreated: whether or not the seeds had been heat-treated
-RowSpacing: spacing of the rows when sowing, narrow=11-13cm, wide=20-25cm
-Ploughing: if ploughing was done in between the previous crop and sowing of the current crop
-FreqSoilDisturbances: the number of soil cultivations done before sowing the crop since the harvest of the previous crop (regardless of purpose of the operation, includes for example harrowing, cultivating and rolling but excluding ploughing)
-FreqWeedTreatment: the number of weeding operations done after the sowing of the crop (harrowing or hoeing)
-MechanicalWeedingStrategy: the type of weeding strategy applied, harrowing or row-hoeing
-Fertilisation_Nperha: the nitrogen fertilisation applied to the current crop, in kg N per ha. Based on fertiliser types and rates given by the farmer, and calculated with standard nitrogen content values from the Swedish board of agriculture (bilaga 10 in https://lagen.nu/sjvfs/2015:21) and reported content in commercial products
-SourceOfFertiliser: the source of the fertilisers applied, manure, non-manure=byproducts from the food or farm industry, combination=both manure and non-manure used, unfert=unfertilised
-CropRotationLeyLength: the normal number of years of ley in the crop rotation or crop sequence of the field
-CropRotationLength: the normal number of years of their crop rotation if a fixed crop rotation was used
-Undersown: was the field undersown with a ley in the current growing season
-PrecropYieldeffect_kgha: the estimated yield increase effect from the preceding crop, calculated from standardised values in Andersson et al., 2022 (tabell 31 in https://www2.jordbruksverket.se/download/18.4627c3ef191fdbf8ba3520f/1726670182663/jo23_17.pdf)
SOIL SAMPLE DATA:
-SoilpH: the measured pH value of the soil samples
-SoilPlantAvailableP: plant available phosphorus in the soil sample, in mg per 100g soil, measured using the ammonium acetate-lactate extraction method
-SoilPlantAvailableK: plant available potassium in the soil sample, in mg per 100g soil, measured using the ammonium acetate-lactate extraction method
-SoilOrganicMatter: organic matter content in the soil sample, in %, estimated by loss of ignition
FIELD MEASUREMENTS:
-SPAD_visit1: nitrogen status of the leaves based on SPAD chlorophyll meter with average of top leaves of the main tiller of 30 plants per plot, unitless, measured in late May to early June
-SPAD_visit2: nitrogen status of the leaves based on SPAD chlorophyll meter with average of top leaves of the main tiller of 30 plants per plot, unitless, measured in late June to early July
-WeedCover_visit1: proportion ground cover of weeds, in %, measured in late May to early June
-WeedCover_visit2: proportion ground cover of weeds, in %, measured in late June to early July
-WeedCover_visit3: proportion ground cover of weeds, in %, measured in mid July to early August
-PropDiseasedLeaves_visit2: proportion of leaves affected with any disease of the three topmost leaves of 15 tillers per plot, measured in late June to early July
-NoAphidsPerTiller_visit2: number of aphids expressed per tiller, calculated from counting aphids of 15 tillers per plot (both leaves and spikes), measured in late June to early July
ADDITIONAL CONTEXTUAL DATA:
-GrowingDegreeDays: Cumulative growing degree Days (based on Daily mean temperatures over 4.5 degrees Celsius) for the field, 27 September 2019 to 1 August 2020 for winter wheat and 19 April to 1 August 2020 for spring Barley. Data from Cornes et al. 2018
-Precipitation: Cumulative rainfall for each field, in mm, 27 September 2019 to 1 August 2020 for winter wheat and 19 April to 1 August 2020 for spring Barley. Data from Cornes et al. 2018
-SoilClayContent: the average clay content of the soil based on a digital soil clay map (Digitala åkermarkskartan; Piikki & Söderström, 2019), in percent
-PropArableWithin1km: estimate of the landscape context and arable intensity around the field by calculating the proportion of arable land within 1km radius from the center of the field. Based on data from the Swedish Environmental Protection Agency, 2018.


Datafile description for "CenteredData_XX.csv" for spring barley (SB) and winter wheat (WW)
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For some parts of the analyses in the related publication the original values were group mean centered based on the mean for each of the two study areas, such that the statistical analyses could be effectively performed with both crops together without getting regional effects. 
The formula for group mean centering was: original value minus the regional average plus global average (of both regions).
The files with centered data contains the following variables from the original data but with group mean centered values:
StudyArea
Yield_kgha
TimeSinceTransition_years, a version of YearOfTransition instead expressed as the number of years since conversion, 2020 minus YearOfTransition
SowingDate_dayofyear
FreqSoilDisturbances
FreqWeedTreatment
Fertilisation_Nperha
CropRotationLeyLength
PrecropYieldeffect_kgha
SoilpH
SoilPlantAvailableP
SoilPlantAvailableK
SoilClayContent
SoilOrganicMatter
SPAD_visit1
WeedCover_visit2
PropDiseasedLeaves_visit2
GrowingDegreeDays
Precipitation
PropArableWithin1km



Reference information
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Abbreviations:
SB = Spring barley, Hordeum vulgare (vårkorn)
WW = Winter wheat, Triticum aestivum (höstvete)
Prop = proportion
Freq = frequency


Data sources:

Data on temperature and precipitation:
We acknowledge the E-OBS dataset from the EU-FP6 project UERRA (http://www.uerra.eu) and the Copernicus Climate Change Service, and the data providers in the ECA&D project (https://www.ecad.eu)
Cornes, R., van der Schrier, G., van den Besselaar, E.J.M., Jones, P.D., 2018. An ensemble version of the E-OBS temperature and precipitation dataset.  Journal of Geophysical Research: Atmospheres. 123. https://doi.org/10.1029/2017JD028200 
Downloaded and used according to ECA&D data policy (https://www.ecad.eu/documents/ECAD_datapolicy.pdf)

Data on soil clay content:
Piikki, K., Söderström, M. 2019. Digital soil mapping of arable land in Sweden – Validation of performance at multiple scales. Geoderma, 352, 342–350. https://doi.org/10.1016/j.geoderma.2017.10.049. 
Downloaded and used according to CC-BY 

Data on land use:
Swedish Environmental Protection Agency, 2018. Nationella Marktäckedata [National Land Use Data]. Naturvårdsverket. https://geodatakatalogen.naturvardsverket.se/geonetwork/srv/swe/catalog.search#/metadata/8853721d-a466-4c01-afcc-9eae57b17b39. 
Downloaded and used according to CC0

Values on estimated yield effect from preceding crop:
Andersson, E., Frostgård, G., Hjelm, E., Kvarmo, P., 2022. Rekommendationer för gödsling och kalkning 2023 [Recommendations for fertilisation and liming 2023]. Swedish Board of Agriculture. Jordbruksinformation. 15:2022. https://www2.jordbruksverket.se/download/18.4627c3ef191fdbf8ba3520f/1726670182663/jo23_17.pdf (In Swedish)

Guideline values of N content in manures:
Swedish Board of Agriculture, 2015. Föreskrifter om ändring I Statens jordbruksverks föreskrifter och allmänna råd (SJVFS 2004:62) om miljöhänsyn i jordbruket vad avser växtnäring. SJVFS 2015:21. https://lagen.nu/sjvfs/2015:21 (In Swedish)


Missing data:
Missing data is written as NA, the missing data stems from either failed field measurements or farmers not remembering the management operations.

Exact geographical location (coordinates) of the fields have been removed from the shared data to ensure that farms cannot be identified, as agreed with the farmers.
