dataesr/scientific-paragraphs-categorization huggingface dataset:
Methods Method and data overview. The main objective of this study was to assemble a consistent and detailed dataset of annual cropland N budgets in Europe 1961-2019. To this end, we collated a range of different datasets. The FAOSTAT database is the primary data source, providing the longest and most complete data on crop and livestock production with global coverage. However, limiting our scope to the former EU28 allows us to leverage the Eurostat database which in certain respects has more comprehensive coverage. The FAOSTAT and Eurostat databases are both based on national statistics, but have several differences in scope and statistical nomenclature. Therefore, as this paper will demonstrate, the two databases in combination provide a richer picture than either one separately. In addition to these international datasets, we have compiled data from several national statistical databases and yearbooks as well as other literature sources.
The main international databases used in this study are listed in Table  1. Remaining data sources are referred to in the text. The focus of this study is cropland, defined as land under arable crops (including temporary grassland) and permanent crops (e. g. , fruit orchards). Cropland does not include permanent grasslands, defined by both FAOSTAT and Eurostat as grassland lasting for more than five years  22, 23. In some cases, however, the results obtained in this work have obvious relevance for permanent grassland as well. For example, our method to estimate synthetic N fertilizer input to cropland also produces an estimate of input to permanent grassland. As explained above, this study covers a territory which today comprises 26 countries. The territory is covered in the period 1961-2019 with the exceptions of Croatia, Estonia, Latvia, Lithuania, and Slovenia, which all Fig.
3 Average rates of synthetic N fertilizer applied to cropland and permanent grassland. The figure shows all countries where more than 3% of the cumulative N fertilizer use has been applied to permanent grassland. The top left panel shows results for the 22 present-day countries which this study covers 1961-2019. gained independence in 1991/1992 and due to data limitations are covered in the period 1992-2019. We follow the nomenclature and regional divisions of the FAOSTAT database. For the period 1961-1999, the FAOSTAT database reports Belgium-Luxembourg as one unit, but since 2000 it reports Belgium and Luxembourg separately. Data are reported for Czechoslovakia 1961-1992, and separately for Czechia and Slovakia since 1993. For the whole period 1961-2019, data are reported for Germany as one unit, the territory known as Germany since the 1990 reunification.
In some cases, the FAOSTAT regional nomenclature differs from other data sources-notably, the Eurostat database covers Belgium and Luxembourg separately since the start in 1955, and only West Germany until 1989-and to reconcile such differences we have collected additional data and calculated area-weighted or quantity-weighted averages as appropriate to the extent possible. To facilitate further analyses, we also provide merged 1961-2019 results for Belgium and Luxembourg and former Czechoslovakia. Throughout the paper, we loosely refer to these geographical areas as "countries". The remainder of this Method section describes and motivates the data and methods used to estimate the following quantities: • Harvested areas and harvested crop N in 17 categories of arable and permanent crops. • Symbiotic N fixation in pulses and forage legumes on cropland.
These data were processed in several steps to identify and address data quality issues. The main steps of this process are illustrated in Fig. 6 , and a detailed description is given in the following sections. The final result of the process is a dataset of areas and N harvests in 17 crop categories (Table  3 ), covering the entire time period defined for each of country. The resulting dataset is found in the data record  12. Rationale for crop categorization. The crop categories listed in Table  3  were chosen to produce a dataset that gives comprehensible and agronomically relevant information about major trends in crop mix and productivity. Specifically, the categorization was made based on the following considerations: • The categories should contain crops with similar N yields and similar N yield changes over time.
For example, wheat and grain maize have had a substantially steeper yield increase than other cereals over time and are therefore reported separately. • The categories should be well-known categories of crops to simplify interpretation and comparison with other datasets. For example, although sugar beets and potatoes are comparable to cereals in terms of N yields and could possibly be grouped according to the previous criterion, we separated them since they are typically separated in agricultural statistics and models. • The categories should make visible the characteristic differences in crop mix between countries. For example, we separated olives and grapes from other permanent crops since these two crops cover 20-30% of the cropland in four Mediterranean countries, compared to about 9% of the total European cropland.
• The number of categories should not be too large because with very small categories the signal-to-noise ratio declines, making any statistical analysis more difficult. crop areas and harvests except fodder crops. From the FAOSTAT crop database, we extracted data on 121 arable and permanent crops. We converted the reported harvests to N quantities assuming crop N contents from Lassaletta et al. 17. The same crop N contents are assumed for all countries in the whole period 1961-2019, even if it is likely that crop N contents have varied both geographically and over time, for several reasons. For example, N contents will tend to increase with dry weather and low yields; N contents will tend to increase with fertilizer rates; and N contents may be may be changed both up and down because of crop breeding.
However, a more detailed analysis of these effects has not been possible in the scope of this study. As described above, we then aggregated these crops to 12 categories listed in Table  3. While the FAOSTAT database has a good level of coverage for most major crops (apart from fodder), there are sometimes data gaps where harvested quantities are reported without corresponding areas. This occurs mainly before 1985 in permanent crops (including olives) and to a lesser extent in the categories "Oilseeds" and "Vegetables and other". For these crops, summing the individual crop areas in a country-year would sometimes result in considerable underestimation of the total harvested area. Similarly, summing areas and harvests separately for available crops would result in incompatible estimates of category areas and harvests.
In order to ensure consistent estimates of category areas and harvests, we therefore took the following approach. For each crop category, we calculated the sums of available crop areas (A sum ) and crop N harvests (H sum ). In addition, based on the crops where both areas and harvests were available, we calculated category-level weighted average N yields (Y est ). Since some area data were missing for individual crops, we additionally calculated an estimate of total category area A est = H sum /Y est. When crop harvests are available but some crop areas are missing, the estimate A est is equivalent to assuming that the weighted average N yield of crops with missing areas is equal to the weighted average yield of the other crops in the same category. For each country and category, we then generated and inspected figures showing the time series of the category-level variables A sum , A est , H sum , and Y est along with available crop-level data on area, harvests, and yields.
In addition, we filled a small number of minor data gaps (e. g. , harvests or areas completely missing during one or a few years) using constant extrapolation. A similar type of problem is when some crops within a category lack area and/or harvest data during a part of the period. This can create a false impression that the category's N yield has suddenly changed abruptly. In a few such cases it appeared more plausible to extrapolate (or sometimes interpolate) areas or yields to obtain a dataset covering the whole period. Generally, these various adjustments made to the default estimates H sum and A est were rather small. The missing olive areas in Greece, Portugal, and Spain were by far the most important adjustments made in this process. In each country, there was less than one percent difference between the default estimate H sum and the final adjusted estimate of total N harvests.
Prior to 1985, these adjustments increased the total crop area by about 1. 5% on average across all countries. Finally, we also explicitly assigned zero harvests and areas where data were completely missing, to obtain a full dataset of the 12 FAOSTAT crop categories in each country. Fodder crop areas and harvests: overview. As mentioned above, the FAOSTAT crop production database excludes most fodder crops. Here, we instead assembled a fodder crop dataset using Eurostat crop statistics (see Table  1 ) and other sources. Eurostat reports areas and harvests of arable and permanent crops in a hierarchy of crop codes  23, 29. The most important category of fodder crops in this hierarchy is "Plants harvested green from arable land" (crop code G0000), which is further subdivided in a number of subcrops as shown in Table  4.
In addition, we included the Eurostat category "Other root crops n. e. c. " (R9000) which mainly accounts for fodder roots, for example Beta vulgaris (known by many names, including fodder or forage beet, or mangold, mangelwurzel, etc. ) and several Brassica species (rutabaga/swede, turnip, etc. )  23. Crop code R9000 does not include roots for seed or human consumption. Other crops used completely or partly for animal feed, including grain legumes, cereals harvested for grain, sugar beets, potatoes, etc. , are accounted for in the FAOSTAT database  30. To our knowledge, the crop codes G0000 and R9000 together account for all the major European fodder crops not included in the FAOSTAT database. In the following sections we describe in detail how we combined data from Eurostat with other sources corresponding to the Eurostat crop codes G1000, G2100, G2900, G3000, G9000, and R9000.
Fodder crop areas. Data extraction from the Eurostat ACS database. Harvested areas are reported in Eurostat's ACS database  23. Data coverage in the Eurostat ACS data varies widely. For some countries, especially the early members of EEC and EU, the area data are complete back to the 1950s. For the more recent EU member states, the data coverage typically starts around the time of their accession application to the EU. For Croatia, Estonia, Latvia, Lithuania, and Slovenia, which in this study are covered starting in 1992, the data coverage is fairly complete. However, for the former communist states of Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Romania, which in this study are covered starting in 1961, there are no data prior to 1987 in the Eurostat database. Eurostat also lacks data during some periods for several countries in western Europe.
In a few cases we cross-checked suspected errors and gap-filled area data from the Eurostat Farm Structure Survey (FSS)  29  (see Table  1 ). However, the FSS data generally have smaller coverage than the ACS and are not entirely comparable in scope and methods, so we used it very sparingly. Some special treatment was needed for crops G9000 and R9000. Crop code G9000 is not reported in the Eurostat ACS, but we summed it from available data of G9100 and G9900. The reason to merge these two crop codes is that their reported areas often fluctuate in such a way to suggest that the same crops have been reported variably as G9100 or G9900; thus, data gaps for the combined G9000 area are fewer and easier to fill than for the individual G9100 and G9900 areas. For R9000 (fodder roots), data were almost never explicitly stated, but could in many cases be calculated as R0000-R1000-R2000  23.
However, since considerable shifts in fodder crop areas actually have occurred since 1961 in most European countries, it is not always straightforward to determine whether abrupt changes in reported areas are reporting errors or accurate representations of historical developments. We therefore scrutinized and cross-checked the Eurostat data against other sources, filling data gaps and making other adjustments to reconcile major discrepancies. The collected dataset on fodder crop areas, as well as figures showing the stepwise gap-filling of fodder crop areas, are available in the data record  12. Fodder roots were important crops in the first half of the 20th century in several European countries, but areas then declined as they were replaced by other, less labor-intensive fodder crops  31.
Therefore we paid special attention to filling data gaps in R9000 areas during the 1960s-1970s. Before listing the data sources and adjustments country by country, we specifically mention the common approach used to fill the long 1961-1986 data gaps in Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Romania. We mainly used data from reports of the Economic Research Service of the US Department of Agriculture (USDA ERS), which during the 1960s-1980s collated information from the statistical yearbooks of the socialist states in a series of reports  [32] [33] [34] [35] [36]. These reports cover the years 1960 and 1965-1987, and give areas for three categories of fodder crops: "feed roots", "corn silage", and "hay". We assigned the former two crop codes R9000 and G3000, which in the overlapping year 1987 agreed perfectly with the Eurostat ACS.
Temporary grasslands (G1000) account only for a few percent of the fodder crops in most of Eastern Europe, and we therefore mostly extrapolated the earliest available G1000 areas back to 1961. Country-specific details are elaborated below. The remainder of this section lists the data sources and adjustments country by country. For brevity, we omit some descriptions of the following minor adjustments: interpolation of minor data gaps, sometimes using data from 1960 or 2020; extrapolation of minor fodder crops accounting for a small share of the total fodder area; removal of obvious outliers. Austria. The Eurostat ACS data are complete and consistent since the start in 1980. Data for 1960 and 1970-79 were filled using national statistics and data from the FAO 1960 World Census of Agriculture  [37] [38] [39].
Remaining data gaps interpolated and extrapolated. Belgium and Luxembourg. The Eurostat ACS data are almost perfectly complete and consistent since the start in 1955. Minor data gaps in G2100 and G2900 areas interpolated. Bulgaria. The Eurostat ACS data are almost complete and consistent since the start in 1987. In 1960-1986, we used G3000 and R9000 areas from USDA ERS publications  [34] [35] [36]  as explained above. In 1987, Eurostat's combined area of G2100 and G2900 matches the USDA ERS "hay" area, so we divided the 1960-1986 hay area between these crop codes in proportion to their 1987 shares, and extrapolated G9000 and G1000 values constant to 1961. Croatia. The Eurostat ACS data are complete from the start in 2000. We extrapolated the areas back to 1992. Czechia. The Eurostat ACS data are complete from the start in 1987 apart from G1000 which is reported at around 10% of the fodder area since 2011.
A lone G1000 value in 1999 is conspicously close to the    23. The crops included in this study and referred to as "fodder crops" are marked in bold face. temporary 1995-1999 decrease in G2900, suggesting a temporary classification change in temporary grassland and legume-dominated crops. Since G1000 data are largely missing, we chose to discard the 1995-1999 decrease in G2900 area and interpolate surrounding values while extrapolating the 2011 G1000 area constant back in time to 1987. Slovakia. The Eurostat ACS data are complete and consistent from the start in 1987 except a minor gap in G2100 and G2900 areas which we interpolated. Czechoslovakia. Areas for 1987-1992 were taken as the sum of the adjusted Eurostat ACS data for Czechia and Slovakia. In 1987, Eurostat's combined area of G2100, G2900, and G9000 matches the USDA ERS "hay" area, so we divided the 1960-1986 hay area between these crop codes in proportion to their 1987 shares.
G1000 was extrapolated constant to 1961. Denmark. The Eurostat ACS data are fairly complete and consistent back to 1955, except for the G9000 area which fluctuates considerably. A closer inspection shows that 1973-2009, G9900 has a large area share while G9100 is not reported; and from 2010 the G9900 area is zero while G9100 has a smaller share. Before 1973, the Eurostat database does not report G9100 or G9900 areas. National statistics show that this apparent discontinuity arises because the reported G9900 area for some years, in addition to cereals harvested green, also includes aftermath, i. e. late season harvests or grazing after other crops. The aftermath at its peak in year 2000 accounted for about half the reported fodder area on arable land but less than 10% of the harvested feed value  40, 41.
Fodder roots made a minor contribution in Finland even in the 1950s and 1960s  46  when they were much more common in other countries. The main feed root seemingly was potatoes  46, 47  , which is already accounted for in the FAOSTAT crop database  30. Considering the lack of further data and the dominance of G1000 in the fodder production we extrapolated the 1998 area of other fodder crops back to 1961. France. The Eurostat ACS data are complete since 1961 apart from a few minor data gaps which we interpolated. Germany. The Eurostat ACS data cover all the fodder crops starting in 1955, but geographically covers only West Germany until 1989. To complete the period 1961-1989, we estimated East Germany's fodder crop areas in 1989 data from Eurostat ACS and USDA ERS  [34] [35] [36]  data as follows.
Similar alfalfa areas are reported from the 1950s until 2017 in multiple overviews of Greek fodder production as well as recent national statistical publications  [48] [49] [50] [51] [52] [53]. In the Eurostat database, however, there are almost no fodder crop data reported for 1988-1999, and from year 2000 the alfalfa area is reported around 10-15 kha. For other forage legumes, the Eurostat data consistently report zero area, while several sources report fairly constant areas in the range 35-70 kha  48, [50] [51] [52] [53]. The area data for fodder crops in the Eurostat FSS 1990-2016  29  are incomplete and offer few additional insights. Based on these considerations, we made the following adjustments to the Eurostat data: discarded the Eurostat area data for G2100 starting in year 2000 and extrapolated the fairly constant areas 1969-1986 to the whole period 1961-2019; assumed a constant G2900 area of 50 kha; interpolated the G9000 area data which appear broadly consistent with various data sources; and extrapolated the average G1000 area from year 2000 back to 1961.
Temporary grassland (G1000) clearly dominates fodder production on cropland. However, a considerable area of temporary grassland has been reclassified to permanent grassland around 1996-2016 although sources disagree on the exact size and timing of this shift. The Eurostat ACS data reports a drop from about 0. 7 Mha to 0. 1 Mha between 1996 and 2000, and a corresponding increase in permanent grassland (crop code J0000) between 2001 and 2002. The Eurostat FSS reports a similar drop in G1000 area between 2013 and 2016. The FAOSTAT database reports a simultaneous change in both temporary and permanent grassland between 2006 and 2008. For consistency with the FAOSTAT permanent grassland area (details below) we used FAOSTAT's temporary grassland area data during 2000-2006, the only period where it disagrees with the Eurostat ACS.
We extrapolated the 2001 areas of G2100 and G2900 back to 1992 and assigned the remainder of the 1992-1999 G2000 area to G1000. This leads to an estimated 95% decrease in the G1000 area between 1999 and 2001, which agrees with an increase in Lithuania's permanent grassland area registered in the Eurostat and FAOSTAT databases since 2001. Most likely this accurately reflects a heavy decrease in the resowing of grasslands in Lithuania which occured after the collapse of the Soviet Union  57. We extrapolated the G1000 area from 1999 to 2000 to agree with the timing of this change in the reported permanent grassland areas. Netherlands. The Eurostat ACS data are complete since 1955 except for minor gaps which we interpolated. The data show an abrupt increase in temporary grassland (G1000) area from less than 40 kha in the mid-1990s to about 200 kha in the mid-2000s, a change which is also reflected in decreased permanent grassland areas in the Eurostat and FAOSTAT databases.
Poland. The Eurostat ACS data are mostly complete since the start in 1987, but only partly consistent with other data sources. The USDA ERS data for 1960-1987  [34] [35] [36]  precisely match the G3000 and R9000 areas in 1987 and we therefore used these without modification. However, the USDA ERS "hay" area in 1987 is considerably smaller than the combined Eurostat G2100 and G2900 areas, which suggests a reporting error in at least one of the datasets. Several factors strongly suggest that the Eurostat G2100 and G2900 areas are both incorrect in 1987-2001. First, Eurostat's reported G2900 area falls by more than 1. 5 Mha in 1987-1998, a change rate which appears unlikely even given the rapid changes taking place in Poland starting in the late 1980s. Second, national statistics from Polish statistical yearbooks  [58] [59] [60] [61]  report that the area of fodder legumes has never been as high as 1.
The following subsections describe the estimation of 2010 yields from available data. Estimating the dry matter yields of fodder crops. The nominal water content of the harvest data is a central concern since harvests may be reported with different nominal water content. Some countries report in dry matter (0% water), while others use crop-specific nominal water content typically between 12% (hay) and 65-80% (e. g. , green maize and other silage crops). The Eurostat ACS data since year 2000 accounts for these differences by reporting the water content ("humidity" in Eurostat's nomenclature) along with the harvested quantities 28. There are two different datasets, one in national humidity (0-88% water content) and one in EU standard humidity (always 65% water content for plants harvested green)  28.
The coverage of humidity values (since year 2000) is not complete, which means that sometimes the harvest is only given in national humidity basis. Prior to year 2000, all the data are given in national humidity basis, without corresponding humidity values. To construct a harmonized dataset of dry matter yields for each country/crop combination, we studied and compared four time series of available yield values: (1) in national humidity, (2) in EU standard humidity, (3) in dry matter based on the national humidity dataset, and (4) in dry matter based on standard EU humidity dataset. For crop code G9000, we calculated production-weighted average yields from data on crop codes G9100 and G9900. Based on a close inspection of these data and sometimes cross-checking against national data sources, we identified the following types of possible reporting errors: • Some crop yields are reported equal in national and EU humidity, although the corresponding humidity values differ.