Title of the dataset:
Biomass production and nutrient content of temperate cover crops

Creators:
- Isabella Selin Norén
ORCID: 0000-0003-2481-3252
Wageningen Plant Research (Open Teelten | Field Crops), Wageningen University & Research
Post box 430, 8200 AK Lelystad
Visiting address: Edelhertweg 1, 8219 PH Lelystad, The Netherlands 
T: +31(0)614317482 of/or T: +31(0)320291174
W: NL www.wur.nl/openteelten | EN www.wur.eu/fieldcrops
- Willem van Geel
info:eu-repo/dai/nl/155679139
Wageningen Plant Research (Open Teelten | Field Crops), Wageningen University & Research
- Janjo de Haan
ORCID: 0000-0002-5686-4348
- Maria-Franca Dekkers (Wageningen Plant Research (Open Teelten | Field Crops), Wageningen University & Research)
- Wiepie Haagsma (Wageningen Plant Research (Open Teelten | Field Crops), Wageningen University & Research)
- Marie Wesselink (Wageningen Plant Research (Open Teelten | Field Crops), Wageningen University & Research)
- Imke Harms (NMI Agro, Wageningen)
- Romke Postma (NMI Agro, Wageningen)

Related publications:
- Selin Noren, I., van Geel, W., de Haan, J. (2021) Cover crop reference values: effective organic matter and nitrogen uptake, Wageningen Research, Report WPR 877 (DOI: 10.18174/544859).
- Harms, I., Postma, R., van der Vegt, K., & de Haan, J. J. (2018). Soil for life: Input values for the organic matter balance: catch crops and crop residues. (NMI-report; No. 1740.N.18). Nutriënten Management Instituut.

Description:
This dataset has been used to establish reference values for organic matter production and nitrogen uptake of ten common monoculture cover crops. It contains cover crop data from several experiments and years of sampling. Most entries contain data on aboveground or belowground biomass. Later entries also contain data on macro- and micronutrient contents. For some entries the soil mineral nitrogen is available. It is possible that additional meta-data and data from other variables can be found if needed. Data used in the report from the 'Clever cover cropping' experiment was excluded from this dataset. A new dataset (containing this and new data) will be published after 2 years.

Keywords:
cover crops
green manure
biomass production
nutrient uptake
nitrogen uptake
NPK
micronutrients
dry matter
organic matter
sowing time
crop height
soil mineral nitrogen

Spatial coverage:
Mostly in the Netherlands; Locations: Lelystad, Wageningen, Vredepeel and Valthermond.
Some entries are from Belgium, Germany, UK, Denmark and Switzerland.

Temporal coverage:
1988-2019

This dataset contains the following files:
Dataset_cover_crops.csv

Explanation of variables:
Crop_long=The cover crop species in English. For mixtures up to the first 4 species are named.
Crop_short=The cover crop species in English. For mixtures Mixture-X is used, at X the number of species is filled in.
Crop_X=The species in separated columns, up to 4 species.
Botanical_name=The latin name of the monoculture cover crop.
Cultivar_variety=The cultivar of the cover crop, or the name of the mixture, if available.
Plant_part=The plant part(s) from which biomass data is available.
Country=The country in which the data was gathered.
Location=The location where the data was gathered, mainly available for Dutch locations.
Field_ID=Identifier of field. Mainly used for own data of recent samplings.
Plot_ID=Identifier of plot. Mainly used for own data of recent samplings.
Soil_type=The soil type where the data was gathered, either clay, loam, sand or reclaimed peat soil(NL:dalgrond).
Pre-crop=The crop grown before the cover crop.
N_fertilisation=The amount of nitrogen fertilisation of the cover crop in kg/ha.
Type_sowing=Either the cover crop is sown after the main crop/pre-crop or it is sown at the same time as the main crop(Sown with main crop), or a short period after the main crop/pre-crop(Undersowing).
Sowing_date=The date of sowing of the cover crop. For literature data the exact date is not always available. For literature data in some cases year 2000 was entered due to lack of information of growing year.
Sowing_week_number=The sowing week number.
Sampling_date=The date of field sampling.
Temperature_sum=Temperature sum from sowing to sampling, using 5 degrees as a base temperature. Data is from the nearest weather station. For undersown crops the harvesting date of the pre-crop was used as starting date for calculating the weather variables. 
Moisture_availability[mm]=The precipiration minus evapotranspiration in mm. The data is from the nearest weahter station. For undersown crops the harvesting date of the pre-crop was used as starting date for calculating the weather variables. 
Radiation[MJ/m2]=The radiation sum in MJ/m2. The data is from the nearest weahter station. For undersown crops the harvesting date of the pre-crop was used as starting date for calculating the weather variables.
Seeding_rate_[kg/ha]=The amount of sowing seed in kg/ha. For literature entries, more data may be able to added from the publications. For mixtures, the amount is listed per species, separated by a comma.
Year_of_study=The growing year, if available, otherwise the publication year.
Source=For literature data a short paper reference. For other data, an identifier for the researcher, sampling coordinator, or sampling year.
Literature_or_measurement=Whether the data was gathered by litearture research of by sampling or compilation of data from within the organisation.
Nmin after harvest_X=The amount of mineral nitrogen in the soil in kg/ha in the given layers (in cm).
Nmin end nov-dec_X=The amount of mineral nitrogen in the soil in kg/ha in the given layers (in cm).
Nmin termination_X=The amount of mineral nitrogen in the soil in kg/ha in the given layers (in cm).
crop_height[kg/ha]=The average height of the cover crop.
Repetitions_aboveground=The number of repetitions on which the aboveground biomass and nutrient uptake values are based.
aboveground_fresh_[kg/ha]=The amount of aboveground biomass before drying.
aboveground _DM_[%]=The dry matter(DM) concentration aboveground biomass.
aboveground _DM_[kg/ha]=The amount of aboveground biomass after drying.
N_uptake_aboveground_[kg/ha]=The amount of nitrogen in aboveground biomass. Calculated by the concentration multiplied by the dry matter biomass.
C_uptake_aboveground_[kg/ha]=The amount of carbon in aboveground biomass. Calculated by the concentration multiplied by the dry matter biomass.
OM_aboveground_[kg/ha]= The amount of organic matter in aboveground biomass. Calculated by the concentration multiplied by the dry matter biomass. 
C/N_aboveground=The ratio of carbon and nitrogen in aboveground biomass.
X_aboveground_[kg/ha]=The amount of nutrient X in aboveground biomass. The different nutrients are Na, K, K2O, Mg, Ca, P, P2O5, Mn, Zn, Fe, Cu, S. The unit may also be in g/ha.
Crude_ash_aboveground_[g/kg_DM]=The concentration of crude ash in aboveground biomass.
Organic_matter_aboveground_[g/kg_DM]=The concentration of organic matter in aboveground biomass. Is determined by taking 1000 minus the crude ash concentration in g/kg DM.
X_content_aboveground_[g/kg_DM]=The concentration of nutrient X in the aboveground biomass. The different nutrients are Na, K, K2O, Mg, Ca, P, P2O5, Mn, Zn, Fe, Cu, S. The may can also be mg/kg.
Column CA-DJ: The same variables as for aboveground biomass but for belowground biomass(roots).
shoot:root_ratio_OM=The shoot root ratio of the OM [kg/ha]
shoot:root_ratio_N_uptake=The shoot root ratio of the N uptake [kg/ha]
DM_total_[kg/ha]=The DM of aboveground and belowground plant matter.
OM_total_[kg/ha]=The OM of aboveground and belowground plant matter.
N_uptake_total_[kg/ha]=The N uptake of aboveground and belowground plant matter.

Literature references:
Allison MF, Armstrong MJ, Jaggard KW, Todd AD (1998) Integration of nitrate cover crops into sugarbeet ( Beta vulgaris ) rotations. I. Management and effectiveness of nitrate cover crops. The Journal of Agricultural Science 130:53–60. doi:10.1017/S0021859697005108.
Grosse M, Hess J (2015) Der kurzfristige Einfluss von drei Zwischenfruchtarten und zwei verschiedenen Bodenbearbeitungen auf Frühjahrs-NO3-N des Bodens und Ertrag der Hauptfrucht Hafer, Eberswalde.
Cougnon M, Vandermoere S, Vliegher A de, Reheul D (2015) Yield comparison of Italian ryegrass and winter rye sown as cover crops after forage maize. Grassland and forages in high output dairy farming systems. Proceedings of the 18th Symposium of the European Grassland Federation, Wageningen, The Netherlands, 15-17 June 2015.
De Ruijter FJ (2012) Afvoer en verwerking van N-rijke gewasresten, Wageningen.
Kolbe H, Schuster M, Haensel M, Gruenbeck A, Schliesser I, Koehler A, Karalus W, Krellig B, Pommer R, Arp B (2004) Zwischenfruechte im Oekologischen Landbau. Fachmaterial Saechsische Landesanstalt fuer Landwirtschaft.
Komainda M, Taube F, Kluß C, Herrmann A (2016) Above- and belowground nitrogen uptake of winter catch crops sown after silage maize as affected by sowing date. European Journal of Agronomy 79:31–42. doi:10.1016/j.eja.2016.05.007.
Hui Xu (2019) unknown title. PhD Thesis University of Ghent, Stefan de Neve.
Möller K, Reents H-J (2009) Effects of various cover crops after peas on nitrate leaching and nitrogen supply to succeeding winter wheat or potato crops. Journal of Plant Nutrition and Soil Science 172:277–287. doi:10.1002/jpln.200700336.
Mueller T, Thorup-Kristensen K (2001) N-Fixation of Selected Green Manure Plants in an Organic Crop Rotation.  Biological Agriculture & Horticulture 18:345–363.
Mutegi, JK, Peterson, BM, Munkholm, LJ, Hansen, EM (2011) Belowground carbon input and translocation potential of fodder radish cover-crop. Plant and Soil 344:159–175
Thorup-Kristensen K (1994) The effect of nitrogen catch crop species on the nitrogen nutrition of succeeding crops. Fertilizer Research 37:227–234. doi:10.1007/BF00748941.
Thorup-Kristensen K (2001) Are differences in root growth of nitrogen catch crops important for their ability to reduce soil nitrate-N content, and how can this be measured. Plant and Soil 230:185–195.
Wendling M, Büchi L, Amossé C, Sinaj S, Walter A, Charles R (2016) Influence of root and leaf traits on the uptake of nutrients in cover crops. Plant and Soil 409:419–434. doi:10.1007/s11104-016-2974-2

Methods, materials and software:
Data from 2018 and 2019:
In the growing seasons of 2018 and 2019 measurements were made in a variety of different cover crop experiments, as well as in farmer fields, on three different soil types; sand, clay and reclaimed peat soil. When sampling in experiments, all repetitions of the treatment were sampled, generally resulting in four samples. Farmer fields were sampled at 4 representative spots. Before sampling, the height of the cover crop was determined in cm above soil level. In mixtures, the highest species determined the crop height. Aboveground biomass from an area of 0.25 m2 was cut at 1-3 cm above the ground and subsequently dried at 70 ℃ for at least 24 hours, after which it was weighed to determine the dry matter biomass. Within the same 0.25 m2 plot 6 soil cores with a diameter of 8 cm were sampled until 30 cm depth, 3 diagonally within the row on top of the crop and 3 diagonally between the rows. Subsequently the cores were rinsed from soil, dead organic matter and stones. The remaining roots were dried and weighed. Cores from the depth 15-30 cm were not rinsed if there were none or a negligible amount of roots present determined by visual assessment. The samples were thereafter analysed for ash, N, P, K and micro-nutrient concentration using accredited and certified methods (Eurofins, 2020).
The methodology of sampling from other years than 2018 and 2019 is available in the original publications (see 'literature references').

This dataset is published under the CC BY (Attribution) license.
This license allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator.

