Introduction

In 2010, the gross value added from agriculture, forestry and fishery in Germany was 19 billion €, thus reaching 0.9% of the total national gross value of approx. 2,240 billion € (BMELV2011). The total agricultural area of 16.83 million hectares in Germany in 2010 included approximately 225,300 ha horticulture and fruit growing areas, with 48.5% vegetable growing, 29.7% tree fruit and soft fruit areas, 8.5% tree nurseries, 7.3% strawberries, 4.2% ornamental plants, and 1.8% gardens (BMELV2011).

In 2010, 87.3% of the fruit growing area (65,502 ha) were used for commercial intensive fruit growing with a yield of 1,152,338 t. This yield was about 21% less than in 2009 while the growing area remained the same. The yields for 2010 for tree fruit types are about 834,960 t for apples, 38,895 t for pears, 49,260 t for plums and prunes, 30,831 t for sweet cherries, 18,265 t for sour cherries, 3,964 t for mirabelles and greengages. In 2010, berry fruit growing yielded currants (11,927 t), blueberries (8,305 t), raspberries (5,212 t), sallow thorn (219 t) and strawberries (150,500 t) (StBA2011a).

The agricultural structure survey of 2007 counted 11,454 tree fruit farms producing for sale in Germany. This is about 20% less than in the 2002 survey (StBA2008b). 56.2% of these fruit growing farms are in Baden-Württemberg, 16.1% in Bavaria, 9.8% in Rhineland-Palatinate, 6.6% in Lower Saxony, 2.6% in North Rhine-Westphalia, and 2.6% in Hesse (StBA2008b). The tree fruit growing area in Germany covers 47,913 ha, with the German Federal Land Baden-Württemberg with 15,153 ha having the largest cultivated area (31.6%), followed by Lower Saxony (18.6%), Rhineland-Palatinate (8.9%), Saxony (8.6%), Bavaria (6.0%), Thuringia (5.1%), North Rhine-Westphalia (4.7%), Brandenburg (4,7%), Saxony-Anhalt (3.5%), Mecklenburg-West Pomerania (3.1%), Hamburg (2.3%), Schleswig-Holstein (1.5%), Hesse (1.2%), and Saarland (0.2%) (StBA2008b).

This production is offset by corresponding research expenses. In 2009, Germany spent 66.65 billion € on research and development, i.e. a proportion of 2.78% of the gross domestic product. The expenses for research and development in public scientific institutions in the area of agricultural sciences were 563.37 million € (StBA2011b). The following Federal Lands had the highest research expenditures in 2009: Lower Saxony (120.3 Mio. €), Bavaria (89.3 Mio. €), Mecklenburg-West Pomerania (69.0 Mio. €), Brandenburg (66.0 Mio. €), Baden-Württemberg (57.9 Mio. €), Hesse (40.6 Mio. €), Thuringia (27.8 Mio. €).

Investments and expenditures in research and development are, in turn, offset by scientific output. The generated knowledge is recorded in scientific publications and available to the scientific community, on the one hand, while providing a location benefit for Germany’s fruit growing sector, on the other. Research results provide a competitive advantage for this sector, e.g. by higher yields, increased product quality or decreased production costs due to optimized production conditions.

The present work aims at a bibliometric survey of the internationally relevant scientific output of tree fruit growing research in Germany, showing these data with regard to individual tree fruit cultures (apple, pear, cherry, plum, apricot and peach), weighing the data and discussing them in light of production data. In addition, developments over time shall be shown.

Material and Methods

The online version of Web of Science® by Thomson Reuters was the only source used for bibliographic and bibliometric analysis. To limit the search to technical and natural science publications, the database of the Science Citation Index (SCI) Expanded (SCI-EXPANDED) for the time between 1945 and today was exclusively used. This database has a current index of more than 8,300 journals covering over 150 natural science disciplines. The database was searched between August 24, 2011 and September 09, 2011.

The search terms were the English trivial name(s) and scientific name(s) of tree fruit species analysed (example: apple OR (Malus ANDdomestica)). To sharpen the search, the trivial name was searched only in the title of the work, while the scientific name was searched in the entire dataset. The search was limited to the interval of 1950–2010 and the document type “article”. The lemmatization function was disabled to prevent assignments due to similar sounding terms (e.g. company names: Appleton). This restrictive search may have omitted some publications but we assume that this is done similarly for all countries.

In a first approach all “articles” of a tree fruit species were collected worldwide and key aspects analysed. In a second approach this selection was limited to Germany and these datasets analysed according to bibliometric criteria and compared in an international context. A scientific original work was assigned to Germany if at least one author had “Germany” or “Fed Rep Ger” or “Ger Dem Rep” or “West Germany” in their address.

Results and Discussion

Apples

In 2009, 71.3 million t of apples were produced worldwide (Faostat2011). In 2011, China alone will produce almost 50% of the world production with an estimated apple production of 33.0 million t, the EU ranking second with an estimated 10.2 Mio. t (Prognosfruit2011) (Fig. 1).

Fig. 1
figure 1

a Apple production in EU-member states in the year 2010 (Prognosfruit2011). Data for Cyprus, Estonia, Finland, Ireland, Luxembourg and Malta were derived from Faostat (2011) and refer to the year 2009.b Apple production of the most important producer countries in the year 2009 are given as an insert (Faostat2011)

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Apples are the most important fruit culture in Germany and with 834,960 t Germany is the fourth largest producer in the EU (Fig. 1a). 9,058 farms grow apples commercially on 31,762 ha (StBA2008b). Until 1987 official statistics listed the entire apple harvest, from 1988 only the production of apples from commercial intensive fruit growing has been recorded (Fig. 2). Since Germany has large meadow orchards, apple growing areas are larger and total apple harvests higher. This explains the higher yields of earlier years and the large variations in the yields of meadow orchards due to pronounced alternate bearing (Fig. 2). Averaging the yields of apple growing in Germany over the years 1950–1985 (1,569,616 ± 538,950 t/a; mean ± standard deviation) and over the years 1992–2010 (937,881 ± 170,324) shows commercial fruit growing in Germany today as being only approx. 2/3 of the entire apple production of the previous Federal Republic.

Fig. 2
figure 2

Apple production in Germany from 1950–2010. The production of the most important apple producing Federal Lands of Germany is shown in stacked bars (data from StBA1953–1990,1990,1991,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001,2002,2003a,2004,2005,2006,2007,2008a,2009,2010,2011a). From 1950–1987 the total apple harvest is reported in the national statistic, whereas from 1988 on only the harvest from commercial intensive fruit growing orchards is reported, without the yield from the meadow orchards. Until 1991 data refer only to the former West Germany, whereas from 1992 on the data comprise all German Federal Lands

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With 5,267 farms on 9,953 ha and its three regions ‘Bodensee’, ‘Rheinebene’, and ‘Neckar-Tauber’, Baden-Württemberg is the largest apple producer in Germany (MLR2011), followed by Lower Saxony with 691 farms on 7,737 ha (StBA2008b). With approx. 10,000 ha, the fruit growing area at the Niederelbe (‘Altes Land’) is the largest connected fruit growing area of Germany and, after South Tyrol in Italy, the second largest in Europe. Saxony ranks third in commercial intensive apple growing (2,828 ha), followed by North Rhine-Westphalia (1,758 ha), Rhineland-Palatinate (1,608 ha), Mecklenburg-West Pomerania (1,255 ha) and Bavaria (1,211 ha). Figure 2 shows the production development in apple growing in Germany between 1950 and 2010.

The fruit production is offset by the output of scientific research in the area of apples. In the surveyed period between 1950 and 2010, 13,207 international original articles about the research on apple growing were published worldwide and listed in the SCI-database (Fig. 3b). 28.7% of these articles have at least one author with a US American affiliation, 7.0% have at least one author from Canada, followed by Great Britain (6.3%), Germany (5.5%), Japan (4.9%), France (4.0%), New Zealand (3.9%), Italy (3.3%), while all other countries are represented with less than 3.0%. Germany thus ranks fourth worldwide. Large apple producing countries often have only a small share of the worldwide scientific output on apple research. Authors from China are involved in only 2.7% of the scientific articles, Brazil and Australia in 2.2%, India and Poland in 2%, Argentina in 0.8%, South Africa in 0.7%, and Chile in 0.5%.

Fig. 3
figure 3

a Relationship of published scientific articles (1950–2010) divided by the apple production of the year 2009/2010 (data from Fig. 1) for the most important apple producing countries worldwide and the EU-member states. The obtained values are represented as relative units (= number of scientific articles per country/ production in tons of the respective country * 1000). Countries are ranked in descending order in the graph.b The insert shows the worldwide published articles on apple research, whereas the number of papers with at least one author from Germany is shown as black bars at the bottom of the insert

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Relating the countries’ scientific original articles on apples published between 1950 and 2010 to the quantities produced in 2009/2010 (data from Fig. 1) results in the ranking shown in Fig. 3a: Finland, Sweden, Denmark, Great Britain, Canada, Switzerland, New Zealand, Australia, USA and Germany are among the top ten countries with a large research output in relation to their production.

Considering only the articles produced in Germany (1950–2010) with at least one author having their address in Germany (black bars in Fig. 3b), 66.8% of the articles were published in English and 31.5% in German. Looking at the publications of the last decade (2001–2010), this language relationship has shifted: English 88.5%, German 10.3%. Despite that fact, apple research is strongly national, because in the period from 1950–2010 only 4.0% of the scientific articles were written in cooperation with the USA, followed by Great Britain (3.2%), Italy (2.9%), Austria (2.3%), France and the Netherlands (2.1%). The last ten years (2001–2010) have seen more internationalization, and 5.4% of the scientific articles were written in cooperation with the USA, Italy (4.8%), Austria (4.5%), New Zealand (3.5%), Switzerland (3.2%), the Netherlands (2.9%).

Assigning the papers to subject areas is certainly not easy but the SCI-database assigns all articles from 1950–2010 with at least one author with German affiliation to the following subject areas: agriculture (36.6% of the articles), plant sciences (31.4%), food science technology (21.7%), chemistry (7.3%), biochemistry and molecular biology (5.2%), entomology (4.0%) etc. Since multiple assignments are possible, these percentages may exceed 100%.

In which journals are the articles written in Germany published? From 1950–2010 the journalGartenbauwissenschaften (laterEuropean Journal of Horticultural Science) ranks first with 15.1% of the articles, followed byAngewandte Botanik (Journal of Applied Botany and Food Quality) with 4.3%‚Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz (Journal of Plant Diseases and Protection) with 4.0%,Deutsche Lebensmittel Rundschau (3.7%),Journal of Agricultural and Food Chemistry (3.3%),Archiv für Phytopathologie und Pflanzenschutz (Archives of Phytopathology and Plant Protection) (3.0%),Erwerbs-Obstbau (1.9%),Molecular Nutrition Food Research (1.9%).

Many non-English journals have only recently been added to the international databases, therefore we see a different ranking when looking at the last decade (2001–2010):Journal of Agricultural and Food Chemistry (6.7% of the articles),Erwerbs-Obstbau (4.5%),Molecular Nutrition Food Research (4.5%),Deutsche Lebensmittel Rundschau (4.2%),Gartenbauwissenschaften (European Journal of Horticultural Science) (4.2%),Angewandte Botanik (Journal of Applied Botany and Food Quality) (4.2%).

The most important institutions for apple research are the consolidated Julius-Kühn-Institutes, the universities of Bonn and Hohenheim, the technical universities of Berlin and Munich and the universities of Hannover, Würzburg, Jena and Kaiserslautern, the Humboldt University Berlin and the Research Centre Geisenheim. These institutions published more than 70% of the scientific papers in the SCI on apples.

Articles on apple research with at least one author with German affiliation also attract international attention. In 2010 these articles were cited 842 times and have a Hirsch factor of 41. The course of citations over time is shown in Fig. 18. All articles published in German between 1950 and 2010 were only cited 35 times in 2010, with a decreasing tendency in the last years, and have a Hirsch factor of 13.

The successful German apple growing and apple production are not only due to scientific research (and the ensuing publications) but also based on a number of institutions focussing on research, applied research and transferring that knowledge to the farmers through intensive practical testing and counselling, and the extension services. These activities rarely result in publications noted by the SCI but contribute considerably to successful production of the fruit growing areas in Germany. Examples are the Kompetenzzentrum Obstbau Bodensee (KOB) in Bavendorf in the South and Esteburg with the Obstbauversuchsanstalt (OVA) of the Chamber of Agriculture Hannover in Jork in the North of Germany.

Pears

In 2009, 22.5 million t of pears were produced worldwide, with 14.4 million t produced in China alone (Faostat2011). In the EU a total of 2.26 million t of pears was produced in 2010, the main producers being Italy (680,000 t), Spain (457,000 t), Belgium (285,000 t), the Netherlands (267,000 t), and Portugal (172,000 t) (Prognosfruit2011) (Fig. 4a). In pear growing, Germany ranks tenth among the EU member states (Fig. 4a). The largest pear producers outside the EU-27 are China, the USA, Argentina, South Korea, Turkey, Japan, South Africa and India (Fig. 4b).

Fig. 4
figure 4

a Pear production in EU-member states in the year 2010 (Prognosfruit2011). Data for Austria, Slovenia, Lithuania, Cyprus, Luxembourg, Latvia and Malta were derived from Faostat (2011) and refer to the year 2009.b Pear production of the most important producer countries in the year 2009 are given as an insert (Faostat2011)

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With 4.4% of the total tree fruit culture area in commercial intensive fruit growing, pears are less important in Germany than cherries and plums. Figure 5 shows the development of pear production in Germany from 1950–2010. Pears are grown commercially in 5,325 farms on 2,101 ha (StBA2008b). Vast meadow orchards are also found in Germany’s pear growing. Until 1987 official statistics listed the entire pear harvest, from 1988 only the production of pears from commercial intensive fruit growing have been recorded (Fig. 5). The graph shows higher yields and more pronounced alternate bearing in the early years (Fig. 5). Averaging the yields of pear growing in Germany over the years 1950–1985 (404,079 ± 116,790 t/a) and the years 1992–2010 (49,810 ± 12,588) shows commercial fruit growing in Germany today as being only approx. 1/8 of the entire pear production of the previous Federal Republic.

Fig. 5
figure 5

Pear production in Germany from 1950–2010. The production of the most important pear producing Federal Lands of Germany is shown in stacked bars (data from StBA; for references see legend of Fig. 2). From 1950–1987 the total pear harvest is reported in the national statistic, whereas from 1988 on only the harvest from commercial intensive fruit growing orchards is reported, without the yield from the meadow orchards. Until 1991 data refer only to the former West Germany, whereas from 1992 on the data comprise all German Federal Lands

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With 2,976 farms on 764 ha, Baden-Württemberg is the largest pear producer in Germany, followed by Lower Saxony with 312 ha (341 farms), Bavaria with 309 ha (981 farms), Rhineland-Palatinate with 210 ha (450 farms), North Rhine-Westphalia with 153 ha (156 farms) (StBA2008b). Pear growing in Germany is characterised by small average farm sizes of 0.39 ha/farm, while the average size for apple growing is 3.5 ha.

The worldwide scientific output in the field of pears is 3,392 international articles for the period of 1950–2010 and limited to scientific original articles listed in the database (Fig. 6b). In 26.2% of the articles at least one author is from the USA, followed by Japan (in 14.5% of the articles), China (5.7%), Spain (5.4%), Italy (5.0%), France (4.8%), Great Britain (4.1%), Germany (3.5%), all other countries have a proportion below 3% of the scientific research output regarding pears. Germany ranks eighth. Some large pear producing countries have only a small share of the scientific output: Turkey (1.4%), South Africa (1.0%), Argentina (0.5%) or Chile (0.3%).

Fig. 6
figure 6

a Relationship of published scientific articles (1950–2010) divided by the pear production of the year 2009/2010 (data from Fig. 4) for the most important pear producing countries worldwide and the EU-member states. The obtained values are represented as relative units (= number of scientific articles per country/ production in tons of the respective country * 1000). Countries are ranked in descending order in the graph.b The insert shows the worldwide published articles on pear research, whereas the number of papers with at least one author from Germany is shown as black bars at the bottom of the insert

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Relating the countries’ scientific original articles on pears published between 1950 and 2010 to the quantities of pears produced in 2009/2010 (data from Fig. 4) results in the ranking shown in Fig. 6a: Sweden, Canada, Norway, Great Britain, Slovakia, Germany, Czech Republic, Jordan, Brazil and Israel are the 10 countries with a large research output in relation to their production. Considering only the articles produced in Germany (1950–2010) on pear research with at least one author having their address in Germany (black bars in Fig. 6b), 84.9% of the articles were published in English and 12.6% in German. Looking at the publications of the last decade (2001–2010), this language relationship has shifted in favour of English: English 94.9%, German 5.1%.

Pear research is also mainly national oriented, because in the period from 1950–2010 only 6.7% of the scientific articles written in Germany were done in cooperation with Austria, followed by Italy (6.7%), France (5.9%), New Zealand (5.9%), the USA (5.0%) and Spain (4.2%).

The main subject areas of pear research in Germany can be seen from the assignment of publications in the SCI. For the period of 1950–2010 these are plant sciences (with 38.7% of the articles), agriculture (30.3%), food science technology (15.1%), chemistry (8.4%), biochemistry and molecular biology (6.7%).

The SCI-database also shows which journals the researchers favour to publish their results. For the period from 1950–2010 these are theZeitschrift für Pflanzenkrankheiten und Pflanzenschutz (Journal of Plant Diseases and Protection) with 8.4% of the articles,Gartenbauwissenschaften (European Journal of Horticultural Science) with 5.9%,Zeitschrift für Lebensmittel-Untersuchung und -Forschung (European Food Research and Technology) with 5.0%,Journal of Horticultural Science and Biotechnology with 3.4% andErwerbs-Obstbau with 2.5%. Considering the last decade (2001–2010) this shows a different ranking:European Journal of Horticultural Science with 8.5%,Erwerbs-Obstbau with 5.1% andJournal of Horticultural Science and Biotechnology with 5.1% of the published articles.

The most important institutions for pear research are the consolidated Julius-Kühn-Institutes, the universities of Hannover, Bonn and Hohenheim, the previous Max-Planck-Institute for Cellular Biology and the Technical University of Munich. These institutions published more than 65% of the scientific papers in the SCI on pears. In 2010, these articles were cited 167 times and have a Hirsch factor of 27. Over the last years citations have shown a steady to slightly decreasing tendency (Fig. 18).

Cherries

In 2009, 2.2 million t of sweet cherries and 1.3 million t of sour cherries were produced worldwide, with 555,430 t of sweet cherries and 342,306 t of sour cherries produced in the EU member states (Faostat2011). The largest cherry producers in the EU are Poland (239,725 t), Italy (124,200 t), Spain (98,219 t) and Hungary (86,878 t) (Faostat2011) (Fig. 7a). With 69,699 t in 2009 Germany ranks fifth within the EU (Faostat2011) (2010: 49,096 t, BMELV2011). In 2009, the largest cherry producers worldwide were Turkey (610,399 t), the USA (550,118 t), Iran (334,546 t) and Russia (239,000 t) (Faostat2011) (Fig. 7b).

Fig. 7
figure 7

a Cherry production in EU-member states in the year 2009 (Faostat2011).b Cherry production of the most important producer countries in the year 2009 as an insert (Faostat2011). Total cherry production includes data for sweet and sour cherries

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In Germany, 6.577 farms produce sweet cherries on 5.482 ha and 2.237 farms produce sour cherries on 3.444 ha (StBA2008b). Cherries are one of the most important tree fruit cultures in Germany, second only to apples. Sweet cherries are grown on 11.4% of the entire tree fruit area in Germany, sour cherries on 7.2% of the area (StBA2008b). The largest growing areas for sweet cherries in Germany are Baden-Württemberg with 2,125 ha (3,725 farms), followed by Bavaria with 600 ha (1,272 farms), Brandenburg with 551 ha (99 farms), Lower Saxony with 537 ha (442 farms), Rhineland-Palatinate with 473 ha (502 farms), Saxony-Anhalt with 353 ha (62 farms), Thuringia with 303 ha (40 farms). For sour cherries, the largest production area is in Saxony with 853 ha (43 farms), followed by Rhineland-Palatinate with 826 ha (514 farms), Thuringia with 631 ha (28 farms), Brandenburg with 286 ha (65 farms), Baden-Württemberg with 221 ha (800 farms), Saxony-Anhalt with 176 ha (36 farms), Bavaria with 111 ha (353 farms).

The overall production development of sweet and sour cherry growing in Germany between 1950–2010 is shown in Fig. 8, indicating the most important production areas. Averaging the yields of cherry growing in Germany over the years 1950–1985 (222,892 ± 55,048 t/a) and the years 1992–2010 (68,249 ± 20,054 t/a) shows commercial fruit growing in Germany today as being only 1/3 of the total cherry production of the former Federal Republic.

Fig. 8
figure 8

Cherry production (sweet and sour cherries) in Germany from 1950–2010. The production of the most important cherry producing Federal Lands of Germany is shown in stacked bars (data from StBA; for references see legend of Fig. 2). From 1950–1987 the total cherry harvest is reported in the national statistic, whereas from 1988 on only the harvest from commercial intensive fruit growing orchards is reported, without the yield from extensive orchards. Until 1991 data refer only to the former West Germany, whereas from 1992 on the data comprise all German Federal Lands

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The worldwide scientific output in the field of cherries is 3,857 articles listed in the SCI for the surveyed period of 1950–2010 (Fig. 9b). In 30.2% of the articles at least one author is from the USA and in 7.9% from Germany. Great Britain (7.3%) ranks third, followed by Canada (5.7%), Japan (5.2%), Spain (5.0%), France (4.3%), Italy (4.0%) and Turkey (3.7%). Several large cherry producing countries have only a small share of the scientific output regarding cherries, e.g. Iran (0.5%), Russia (0.5%), Serbia (0.2%).

Fig. 9
figure 9

a Relationship of published scientific articles (1950–2010) divided by the total cherry production of the year 2009 (data from Fig. 7) for the most important cherry producing countries worldwide and the EU-member states. The obtained values are represented as relative units (= number of scientific articles per country/production in tons of the respective country * 1000). Countries are ranked in descending order in the graph.b The insert shows the worldwide published articles on cherry research, whereas the number of papers with at least one author from Germany is shown as black bars at the bottom of the insert

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Relating the scientific output in the field of cherries for the period of 1950–2010 to the production data for 2009 (data from Fig. 7) of the same country results in the ranking of the countries having relatively many research results compared to their production: Sweden, followed by Great Britain, Luxembourg, the Netherlands, Slovakia, South Africa, Latvia, Mexico, Estonia and New Zealand (Fig. 9a).

From the articles published in Germany from 1950–2010 (Fig. 9b, black bars), 63.8% are in English and 34.2% in German. Looking at the last decade (2001–2010) this language relationship has clearly shifted in favour of English (English: 86.7%, German 12.4%). With regard to joint publications, only 5.3% were published with the USA, followed by Spain (2.0%) and Switzerland (1.6%).

The papers published in Germany between 1950 and 2010 can be assigned to the following subject areas: agriculture (38.2%), plant sciences (34.9%), food science technology (10.9%) and biochemistry and molecular biology (6.6%). The five most frequently used journals for German cherry research areGartenbauwissenschaften (European Journal of Horticultural Science) (17.4% of the articles),Angewandte Botanik (Journal of Applied Botany and Food Quality) (4.8%),Scientia Horticulturae (4.9%),Zeitschrift für Pflanzenkrankheiten (Journal of Plant Diseases and Protection) (4.7%), andPhytochemistry (2.6%).

The most important institutions for cherry research are the Technical University of Munich, the consolidated Julius-Kühn-Institutes, and the universities of Halle, Hohenheim, Bonn and Giesen. These institutions published more than 54% of the scientific literature on cherries in the period of 1950–2010.

The articles on cherry research with at least one author affiliated in Germany were cited 333 times in 2010 and have a Hirsch factor of 31. Over the last years citations have shown a rather steady tendency (Fig. 18).

Plums

In 2009, 10.8 million t of plums and sloes were produced worldwide, with 1.6 million t produced in the EU (Faostat2011). The main producers in the EU are Romania, France, Spain, Italy, Poland, Germany, Austria, Hungary, Great Britain and Portugal (Fig. 10a). Outside the EU, China covers 50% of worldwide production with close to 5.4 million t, followed by Serbia, the USA, Chile, Turkey and India (Fig. 10b).

Fig. 10
figure 10

a Plum and sloe production in EU-member states in the year 2009 (Faostat2011).b Plum and sloe production of the most important producer countries in the year 2009 (Faostat2011)

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In Germany, plums and prunes are grown in 6,864 farms on 4,564 ha, mirabelles and greengages in 2.623 farms on 561 ha (StBA2008b). With regard to acreage, plum growing is the third most important tree fruit culture in Germany covering 9.5% of the entire tree fruit area in Germany. Figure 11 shows the development of plum growing in Germany from 1950–2010, with plums, prunes, mirabelles and greengages combined. Averaging the yields of plum growing in Germany over the years 1950–1985 (436,614 ± 146,059 t/a) and the years 1992–2010 (50,975 ± 15,754 t/a) shows commercial fruit growing in Germany today as being only approximately 1/8 of the entire plum production of the former Federal Republic.

Fig. 11
figure 11

Production of all types of plums, mirabelles, and greengages in Germany from 1950–2010. The production of the most important Federal Lands of Germany is shown in stacked bars (data from StBA; for references see legend of Fig. 2). In the national statistics from 1950–1987 the overall total plum harvest is compiled, whereas from 1988 on only the harvest from commercial intensive fruit growing orchards is reported, without the yield from extensive orchards. Until 1991 data refer only to the former West Germany, whereas from 1992 on the data comprise all German Federal Lands

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With 3.852 farms on 1,870 ha Baden-Württemberg is the largest plum producer in Germany, followed by Rhineland-Palatinate with 986 ha (695 farms), Bavaria with 571 ha (1,339 farms), Lower Saxony with 278 ha (336 farms), North Rhine-Westphalia with 190 ha (171 farms), Thuringia with 180 ha (35 farms) (StBA2008b). Plum growing in Germany is also characterised by small average farm sizes of 0.66 ha/farm.

The worldwide scientific output in the field of plums is 2,168 international articles for the period of 1950–2010 and limited to scientific original articles listed in the SCI-database (Fig. 12b). In 26.2% of the articles at least one author is from the USA, followed by Spain (10.8% of the articles), France (8.7%), Italy (5.7%), Germany (5.5%), Great Britain (4.6%), Canada and Japan (3.8%). The large plum producing countries have only a small share of the scientific output regarding plums: China (2.0%), Serbia (0.5%), Chile (0.3%), Turkey (2.1%), India (1.7%), Iran (0.3%). Germany ranks fifth.

Fig. 12
figure 12

a Relationship of published scientific articles (1950–2010) divided by the plum production of the year 2009 (data from Fig. 10) for the most important plum producing countries worldwide and the EU-member states. The obtained values are represented as relative units (= number of scientific articles per country/ production in tons of the respective country * 1000). The ranking of the countries is shown.b The insert shows the worldwide published articles on plum research, whereas the number of papers with at least one author from Germany is shown as black bars at the bottom of the insert

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Relating the countries’ scientific original articles on plums published between 1950 and 2010 to the quantities produced in 2009 (data from Fig. 10) results in the ranking shown in Fig. 12a: Belgium, Slovakia, Canada, Sweden, Denmark, Norway, Tanzania, New Zealand, Czech Republic, Great Britain are the 10 countries with a large research output in relation to their production. Considering only the articles produced in Germany, i.e. publications for the period of 1950–2010 and in the field of plum research with at least one author having their affiliation in Germany (Fig. 12b, black bars), 63.9% of the articles were published in English and 34.4% in German.

Between 1950 and 2010, only 4.2% of the scientific articles written on plum research in Germany were done in cooperation with the USA, followed by Great Britain, France, Italy and Spain with 2.5% each.

The most important subject areas in plum research in Germany can be seen in the assignment of publications in the SCI. For the period of 1950–2010 these are plant sciences (with 31.9% of the articles), agriculture (30.3%), virology (10.9%), environmental sciences and ecology (9.2%), food science technology (8.4%), etc.

The database also shows which journals the researchers favour to publish their results in the field of plum research. For the period from 1950–2010 these areGartenbauwissenschaften (European Journal of Horticultural Science) with 17.6%,Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz (Journal of Plant Diseases and Protection) with 5.9%,Zentralblatt für Mikrobiologie (Microbiological Research) with 5.9%,Journal of General Virology with 5.0% of the articles.

The most important research institutions for plum re-search are the consolidated Julius-Kühn-Institutes, the universities of Hohenheim, Hannover, Bonn, Halle and the Technical University of Munich. These institutions published about 65% of the German scientific articles on plums in the SCI. In 2010 these articles were cited 73 times and have a Hirsch factor of 19. Over the last years citations have shown a steady or decreasing tendency (Fig. 18).

Apricots and Peaches

In 2009, 3.7 million t apricots were produced worldwide, 0.7 million t in the EU (Faostat2011). The 10 most important producers in the EU are Italy, France, Spain, Greece, Hungary, Romania, Austria, Bulgaria, Poland and Portugal (Fig. 13a). Outside the EU these are Turkey, Iran, Uzbekistan, Algeria, Pakistan, Morocco, Ukraine, Japan, Egypt and Syria (Fig. 13b) (Faostat2011).

Fig. 13
figure 13

a Apricot production in EU-member states in the year 2009 (Faostat2011).b Apricot production of the most important producer countries in the year 2009 (Faostat2011)

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In 2009, the worldwide production of peaches and nectarines was 20.3 million t, with the EU producing 4.2 million t in 2009, mainly in Italy, Spain, Greece, France, Hungary and Portugal (Fig. 14a). The main producer outside the EU is China with 10.2 million t, followed by the USA, Turkey, Egypt, Iran, Chile, Argentina, India, Brazil and Mexico (Fig. 14b) (Faostat2011).

Fig. 14
figure 14

a Peach and nectarine production in EU-member states in the year 2009 (Faostat2011).b Peach and nectarine production of the most important producer countries in the year 2009 (Faostat2011)

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In Germany, apricot and peach growing has lost its importance so that official statistics ceased analysing production in 2006 (StBA2007). The last survey of agricultural area utilization in 2002 (StBA2003b) mentions an apricot acreage of only 53 ha (202 farms) in Germany. Peaches are still grown on 103 ha (525 farms). This is 0.1% of the entire tree fruit area in Germany for apricots and 0.2% for peaches.

Figure 15 shows a summary of the production development for apricot and peach growing in Germany from 1950–2005, with the main production areas highlighted. Averaging the yields of apricot and peach growing in Germany over the years 1950–1985 (31,619 ± 13,695 t/a) and over the years 1992–2005 (952 ± 336 t/a) shows commercial fruit growing in Germany today as being only approximately 1/33 of the entire apricot and peach production in the former Federal Republic.

Fig. 15
figure 15

The sum of apricot and peach production in Germany from 1950–2010. The production of the most important Federal Lands of Germany is shown in stacked bars (data from StBA; for references see legend of Fig. 2). In the national statistics from 1950–1987 the overall total apricot and peach harvest is compiled, whereas from 1988 on only the harvest from commercial intensive fruit growing orchards is reported, without the yield from extensive orchards. Until 1991 data refer only to the former West Germany, whereas from 1992 on the data comprise all German Federal Lands

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The worldwide scientific output in the field of apricots is 1,428 international articles for the period of 1950–2010 and limited to scientific original articles listed in the SCI-database (Fig. 16b). In 14.1% of the articles at least one author is from Spain, followed by the USA (11.3% of the articles), Turkey (10.6%), Japan (9.5%), France (8.2%), Italy (6.4%), China (5.3%), India (2.9%), Hungary (2.6%) and Germany (2.6%; Fig. 16b, black bars). The scientific output for peaches and nectarines for the same period is 5,451 international articles (Fig. 17b). 36.8% of these articles come from the USA, followed by Spain (7.6%), Italy (6.8%), France (6.3%), Japan (5.2%), Brazil (4.1%), Canada (4.0%), China (3.7%), Australia (2.9%) and Greece (2.4%). Germany has a share of 1.3% of the articles.

Fig. 16
figure 16

a Relationship of published scientific articles (1950–2010) divided by the apricot production of the year 2009 (data from Fig. 13) for the most important apricot producing countries worldwide and the EU-member states. The obtained values are represented as relative units (= number of scientific articles per country/ production in tons of the respective country * 1000), and the ranking of the countries is shown.b The insert shows the worldwide published articles on apricot research, whereas the number of papers with at least one author from Germany is shown as black bars at the bottom of the insert

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Fig. 17
figure 17

a Relationship of published scientific articles (1950–2010) divided by the peach and nectarines production of the year 2009 (data from Fig. 14) for the most important peach and nectarines producing countries worldwide and the EU-member states. The obtained values are represented as relative units (= number of scientific articles per country/ production in tons of the respective country * 1000), and the ranking of the countries is shown.b The insert shows the worldwide published articles on peach and nectarines research, whereas the number of papers with at least one author from Germany is shown as black bars at the bottom of the insert

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Relating the countries’ scientific original articles published between 1950 and 2010 to the quantities of fruit produced in 2009 (data from Figs. 13 and14) results in the ranking shown in Fig. 16a: Germany, Canada, New Zealand, Mexico, Czech Republic, Slovenia, Israel, India, the USA, and Australia are the 10 countries with a large research output in relation to their production of apricots. The ranking for peaches and nectarines is Germany, Switzerland, Canada, Slovakia, Kenya, Czech Republic, New Zealand, Japan, the USA and Austria (Fig. 17a). In both cases, Germany is among the countries with active international research in relation to their production in these fields.

Considering only the articles produced in Germany, i.e. the publications between 1950 and 2010 with at least one author having their address in Germany (Figs. 16b and17b, black bars), 78.4% of the articles on apricot research were published in English and 18.9% in German. This relation is similar for peach research: 78.3% English and 17.4% German.

Regarding joint publications, 10.8% of the scientific articles on apricot research written in Germany between 1950 and 2010 were done in cooperation with Israel, 8.1% with the USA and 5.4% with Hungary. In peach research, 13.0% of the articles were published in cooperation with Spain and the USA, 11.6% with Italy and 4.3% with Brazil.

The most important subject areas of apricot research in Germany can be seen from the assignment of publications in the SCI-database. For the period of 1950–2010 these are food science technology (35.1%), agriculture (29.7%), chemistry (27.0%), environmental sciences ecology (13.5%), and plant sciences (with 13.5% of the articles). For the area of peach research the focus is on agriculture (29.0%), plant sciences (21.7%), chemistry (20.3%), food science technology (18.8%) and entomology (14.5%).

For the period of 1950–2010 the following journals were favoured in the field of apricot research:Journal of Agricultural and Food Chemistry with 13.5% of the articles, followed byOecologia with 10.8%,Flora andFood Chemistry with 8.1% each. In the field of peach research these are theJournal of Agricultural and Food Chemistry with 8.7% of the articles, followed by theJournal of Horticultural Science (5.8%) andEntomologia Experimentalis et Applicata,Helvetica Chimica Acta andZeitschrift für Angewandte Entomologie (Journal of Applied Entomology) with 4.3% each.

The most important institutions of apricot research from 1950–2010 were the universities of Würzburg, Hohenheim, Bonn and Hannover, the Technical University of Munich and the Research Centre Jülich, with a total of approx. 55% of the publications. In the field of peach research these are the universities of Göttingen, Bonn, Hohenheim, Erlangen and Würzburg, the Paul Ehrlich Institute and the consolidated Julius Kühn-Institutes with a total of more than 50% of the publications. It is noticeable that most publications have been in international media in the last decade. In the period of 2001–2010, 48% of all apricot articles and 50% of all peach articles (from 1950–2010) were published by authors from Germany.

Conclusions

Per capita consumption of fruit and vegetables in Germany is 125.5 kg/a for fruit and 92.3 kg/a for vegetables (business year 2007/08; BMELV2011). Since 1996/97 average fruit consumption has increased by approximately 1.2% per year, that of vegetables by 0.1%. This may be due to the consumers‘ increased nutritional awareness and campaigns like “5 a day—for better health” where increasing consumption to 400–800 g/day of fruit and vegetables is said decrease cancer incidence by 30–40% (WCRF1997).

The annual per capita consumption of fruit of 125.5 kg/a includes 71.8 kg/a of fresh fruit, 48.3 kg/a citrus and tropical fruit, 3.8 kg/a nut fruit and 1.6 kg/a dry fruit (BMELV2011). Germany has a very large share of meadow orchards (Figs. 2,5,8,11 and15) and fruit consumption from meadow orchards and gardens is estimated to be approximately 25 kg/a and inhabitant. This amount must be added to the above per capita consumption of 125.5 kg/a from commercial growing (BMELV2011). Apples are the most important fruit in Germany, their per capita consumption as dessert fruit is approximately 18 kg/a. Including juices and convenience products, the per capita consumption of apples increases to approximately 30 kg/a (BMELV2010). In 2010, Germany consumed 469 million l of apple juice (Schwartau2011).

Germany’s self-supply with fruit is a low 22.4%. Approximately 7.6 million t of fruit are imported, 2.9 million t exported. Adding a usable production of approximately 1.3 million t results in a domestic use of approximately 6.0 million t of fruit (2009/2010; BMELV2011). In 2010, 621,502 t of apples (mainly from Italy, the Netherlands, France, Belgium, Austria and the Czech Republic; BLE2011a), 22,495 t of sweet cherries (mainly from Spain, Greece and the Netherlands) and 16,425 t of sour cherries (mainly from Hungary, the Czech Republic, Austria and Belgium; BLE2011b), and 88,527 t of peaches and 186,872 t of brugnons and nectarines (mainly from Italy and Spain; BLE2011c) were imported in Germany. 164,428 t of pears (mainly from Italy, the Netherlands, Spain and France; data 2009, BLE2010b) and 46,393 t of plums and sloes (mainly from Spain, Italy and Hungary; data 2009, BLE2010a) must be added. Fruit produced in Germany has a production value of 794 million € (BMELV2010).

Research and innovation in the field of fruit growing are important to increase competitiveness of national fruit production against other fruit growing areas with quality products and to become more independent from imports in terms of quantity. Based on the number of articles published in Germany, the ranking is as follows: Apples, cherries, pears and plums, peaches and apricots. This ranking is also indicated by the number of citations (Fig. 18). This scientific output is offset by the production data with apples being produced in the largest quantities, followed by cherries, plums, pears, peaches and apricots.

Fig. 18
figure 18

Number of citations of articles with at least one author with a German affiliation, regarding the fruit sector

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Within the EU Germany ranks fourth in apple production (2009/2010) (Fig. 1a), tenth in pear production (Fig. 4a), fifth in cherry production (Fig. 7a), sixth in plum production (Fig. 10a), and 15th in the production of apricots and peaches (Figs. 13a and14a). However, Germany’s output of scientific articles is rather high compared to the corresponding production, e.g. Germany ranks tenth for apple (Fig. 3a), sixth for pears (Fig. 6a), 21st for cherries (Fig. 9a), 17th for plums (Fig. 12a) and first for apricots and peaches (Figs. 16a and17a) worldwide.

Today’s science language is English, however, especially agriculture is regional and highly territorial. This isevidenced in the language used for original articles written in Germany, because over a period of 60 years (1950–2010) 31.5% of the original articles on apples were published in German, 12.6% on pears, 34.2% on cherries, 34.4% on plums, 18.9% on apricots and 17.4% on peaches. Considering only original articles of the last 10 years, the share of articles in German decreases to approximately 5–15%.

With regard to the absolute output of scientific original articles Germany ranks fourth worldwide for apples, eighth for pears, second for cherries, fifth for plums, ninth for apricots and 14th for peaches. This shows that Germany is in the international top group regarding research on tree fruit and is able to support economic competitiveness of German fruit growing regions with scientific knowledge.