Journal Citation Studies. 53. Agricultural Sciences: Most Fruitful Journals and High Yield Research Fields

Current Comments” EUGENE GARFIELD INSTITUTE FOR SC1:hTIFiC !RWKMATIGP$B 3501 MARKET ST PHILAGE.R+IA, PA 19104

Number 51 December 17, 1990 Citation data for agricultural science journals indexed in the 1989 Science Cifarion Ibex ~ are examined. Impact factors, journals most cited by these “core” journals, and those that most frequently cited the core journals are identified. Highest impact articles and most active research fronts in the agricultural sciences also are presented. Based on these data, nine journals are identified as occupying a prominent position in the field.

Introduction: A Brief Overview herds and cultivated crops. Based on ar- of Agriculture chaeological findings, researchers believe that primitive agriculture developed as early Last October, I participated in a sympo- as 9003-7000 BC in the Near East. The sium on peer review and editing at the an- Natufians of Palestine used sickfes during nual meeting of the American Society of this period, though it is unclear whether Agronomy (ASA) in San Antonio, Texas. At they harvested wild or sown grains. There the invitation of Bob Sojka and Hank May- are also indications that wheat and barley kurd, Agricultural Research Service, US De- were cultivated as early as 7000 BC in what partment of Agriculture (USDA), Kimberly, is now lran and Iraq.3 Idaho, I presented a citationist perspective However, the popular conception that the on how the ASAs key publications compare Middle East was the single center of agr- with other journals of agricultural research. 1 icultural development is no longer sup- While this presentation understandably fo- ported. Domesticated beans, gourds, and cused on ASA journals, the data we pre- water chestnuts seem to have been grown in pared gave us an opportunity to provide an Thailand approximately X00 BC, and pep- overview of the agricukumf sciences litera- pers, avocados, beans, pumpkins, and ture as part of our continuing series of jour- gourds also were domesticated in the Amer- nal citation studies. icas by 7000-5000 BC.3 The agricultural sciences today span a broad spectrum of research on virtually all Justus von Liebig and the Growth aspects of feud production. This includes of Scientific Agriculture farm production, soil cultivation and conservation, the growth and harvesting of food Agricultural knowledge remained an orrd crops as well as forage and feed for animals, tradition, with information transmitted ver- animal husbandry, and t!!e. processing of bafly from farmer to farmer, until the turn of pIant and animal products for consump- the nineteenth eenttrry. Agricultural science tiotr,z did not gain a place in academia until the The rise of agncuhuraf knowledge has first agricultural academies were established been traced back to ancient times, when hu- in Hungary in 1796 and Germany in 1818. mankind made the transition from nomadic The earliest effort to put agriculture on an hunting/gathetirrg tribes to more settled so- empirical, scientific footing is credited to cieties supported by domesticated animal Justus von Liebig, a German chemist who

455 Tabfe 1: Cors amicufture ioumals. 1989 SCf ’, in abhabelic order by wbliifser, with their years of origin (in pamntheaes), ~ 1989 im~ct factors. (See Table 2 for explanation of im~~i f=tor caJcultstimts.)”

Academic Press, US Field Crops Research (1977) 0.63 Advances m Agronomy ( 19’$9) 1.03 Geoderma ( 1967) 0.56 Ag’icultuml fnsfitute of Canada Soi[ & Ti/@e Research ( 1980 ) 0.53 Canadian Journal of Soil SCrence (1957 ) 0.73 Elsevier Applied Science, UK Akademie Vedag, Germany Agriadfund Systems (1976) 0.40 Archtv@ Auker- wrd Pflan:enbau und ftm/ogica/ Wasfes (1979) 0.21 Bodenkurufs’ (1971) 0.24 Biomass (198 1) 0.48 ,kimqvist & Wiksell, Swe&n Jourrwzl of the Sctence of Food and Smedish Journal @Agricultural Research ( 1933) 0.29 Agrictdrwe (1950) 0.68 Amenmn Chemical Smiety Pesric/de Science (1970) I,02 Jourml of Agricultural and Food Entomological Society of America C’hemi.srq (1953) 1.20 Journal of Economic Entomology (1908) 0.74 American society of Agricultural Engineers European Association for Potato Research, Tramacfions of the ASAE ( 19!?7) 0.37 The Netherlands American Snciety of Agronomy F’ofato Research ( 1958) 0.33 Cmp Science Society of America European Weed Research .%iety, UK Soil Science Scciety of America Wet-dResearch (1% 1) 0.35 Agronom! Journal (1‘X)7) 0,7 I Mtuto Spsnmentale per la Cerealicohra, ltaly Crop .scwznce([961) 0,61 Maydica (1956) o,~o Soil Science Socidy of America Journal ( 1936) 1,18 Intematiomd Be Research Assocuthon, UK American Society for Enolog y and Wticultm Bee World (19 19) 0.19

Anav-ican Journal of Enology and JG i+&SS, US Vilwldmre ( I948) 0.66 Ltimyc{e ( 1960) 0.22 Blackwell Scientific, UK Kluwer. The Netherlands Journal ofSoil Science (1949) 0.95 .Euphyrica (1952) 0.39 British Sxiety for Research in Agricultwal Pkmr md. soil ( 1948) 0.69 Engineering Kyushu University, Japan Academ]c Press, UK Journal of the Faculty of Agrlcuhwe, Jourmd of Agric’uhurul Engineering Kyushu Umw’rsity (1923) 0.13 Research (1956) 0,23 Japan .%ciety for Bimcience, Butterworth-Heinem, UK Biotecfuwlogy, and Agmchemistry Crop Proferfmn (1982) 0,45 Agrmdrurcd and ffio/ogica/ Chsmis/V ( 1961) 0.86 Tropical Agr;culfare (1924) 0,11 Japanese society of Soil Science and Plant Nutrition CAB Soil Scmce and P/unr Nurri(ion ( 1955) 0,52 Perganson Press, UK Macel D&k, US Outkwk on Agriculture (1956) 0.25 Communications in Soil ScWnce and Cambridge University Press, UK Pfanr Anulysis (1970) 0.47 Eqwrimerwd Agricukre (1933) 0.25 Journal of Environmental Science Journu/ of Agricu/omd Science ( 1935) 0.49 and Health Part B-- Pestickies, Food Canadian Society of Agricultural Engineering Contandnants ami Agricfdtural Wastes (1976) 0.60 Canadian Agricultural Engineering (1959) 0.34 PergamwmPress, UK Council of Scientific and Industrid Research Journal of Stored Products Research ( 1%5 ) 0.28 Orgamzations, AustraJia .soi[ Bmk)gy & Lkckmistq (1%9) 1.31 Aus!rolian Journal <$A,yricultura/ Pesticide Science ~Iay of Japan Research (1950) 0,74 Journal of Pesricide Science (1973) 0,54 Australian Journal ofEqerinteftfal Potato Association of America Agricu/mre (I% 1) 0.40 American Potato Journal (191 3) 0.40 Australian Journal of Soil Research (1963) 0,s4 RoyaJ Netherlands Society for Agicukuml science Tropical Grasslands (1%7) 0.11 Netherlands Journal of’Agriculnwol DSfR, New Zealand Scwrce ( 1953) 0.36 New Zzalaml Journal

456 Verband der C1garettmiodustrie, Germany Journal of Agronomy and Crop Scienc+ Lfeitrage MI Tabaiforschung Zeimchrft fiir Acker- und Pffnrrzetdkru (1853) 0.16 Internatiorrcd(l%l ) 0.50 Pfant Breedirr@itschr frfiir Vdxsmks Oeuwcher Lsndwirtschnfttkk PJ7arrzerrzuchtwrg(1912) 0.7I Urrtem.uchungs und Forxhungssnstelten Weed Science Sockry of America %uerkmder, Genrwmy Weed Science (1951) 0.59 Agribiological Research: i?eitschrfrftir Wiley, US Agrarbiologie-.,4grikultwchernidko@ie .%vier Soi/ Science (1959) 00s (1949) 0.32 Wdliams & WMim, US V.lag PSU1Parey, Germany Soil .Science ( 1916) 0.65 taught at the Universities of Giessen and what has since been acclaimed as one of the Munich in the early and mid- 1800s.z.4 most important books in the history of sci- Liebig is best known for his many contri- entific agriculture, Organic Chemistty in Its butions to the development of organic Applications to Agriculture and Physiol- chemistry. He systematicrdly extended this ogy.5 Among the landmark topics it dis- knowledge to agriculture and plant physiol- cussed were the role of carbon in plant nu- ogy, and ultimately put forward the most trition, the source of nitrogen for plant comprehensive treatment of plant nutrition uptake, and the purpose of fertilizers in sup- presented to that time. In 1840, he published plying ammonia and various salts to plants.4 Frederic L. Holmes, University of West-

Tabte 2 Core agriculture journafs with impact fac- ern Ontario, London, Canada, summarized tors of at least 0.50, 1989 JCR e tnrpactfactnrs are Liebig’s impact on practical and scientific cntculated by dividing 1989 citations to a journal’s agriculture: 1988 and 1987 srticles by the number of srticles it published in tbe two years. Before 1840 it was generally believed that troth plant and animal life were dependent 1989 1988+1987 1989 on the circulation of an organic, pre- Journal Impact Arttdes Citations- Soil Biol. Biochcm. 1:31 283 371 viously living material. Now, whatever J. Age Fowt Chem. 1.20 54s 658 opinion individuals held on spezific Soil Sci. SW. Amer J. 1,18 638 756 points, they agreed that the nutrient sub- Hilgardii 1.06 16 17 stances of plants were inorganic. That Pestic. Sci. 1.02 187 lW change had transformed the objectives of Advarr. Agmn. 1.00 10 10 agriculture for under the older conception J. Soil Sci. .95 125 119 the potentiat production of frmdstuffs A~, Biol. Chem Tokyo .86 1,225 1,051 would seem to have a fixed limit, whereas Aust. J, Soil Res. .84 112 94 Biol. Fat. Soils .79 210 165 in the new view ao unbound increase in Aust. J, Agf. Res. .74 191 141 organic life appeared possible. J, Econ. Emomol. .74 594 439 Liebig’s students and followers pro- Can. J. Soil Sci. ,73 171 124 vided much of the means for the rigorous Agmn. J. .71 386 275 scientific study of agriculture that he envi- Plant Breeding .71 190 134 sioned, as they began to set up experiment Plant Soil .69 674 467 stations in Europe and the United States.4 J. Sci. Fcod Aq. .68 307 208 (p. 348) Amer. J. Enol, Vkicult. .66 122 81 Soil Sci. .65 220 143 Whh the momentum built up by Liebig Agr. Forest Meteorol. .63 145 91 Field Cmp Res. .63 104 65 and his followers, a number of agricultural Crop Sci. .61 747 456 colleges were founded in the US. In 1853, J. Environ. Sci. Heat. B .60 82 49 the f~st state agricultural college was estab- J. Soil Water Ccmserv. .59 1% 116 lished in New York. The oldest surviving Weed Sci. .59 3CS3 178 one, however, was established in Michigan irrigation Sci. .58 45 26 Apidologie ,56 61 34 in 1857 and is now known as Michigan Gealemna .56 94 53 State University. In 1862, the Mornll Act J. Pestic. Sci. .54 132 71 was passed by Congtess and signed by Pres- 98 52 Soil TO(. Res. .53 ident Abraham Lincoln, This act endowed Soil Sci. Pfarrt Nutr. .52 122 64 Beitr, Tabakforsch. .50 14 7 so-called “land-grant” colleges for the pur-

457 poses of agricultural research and teaching. nal citation studies. We wilI start with a In 1887, the Hatch Act provided federal group of 66 agriculture and soil science support for cooperative agnculturti research journals indexed in the 1989 Science Cifo- between state colleges and the USDA. By rion index’@ (S0 Q), and present rankings 1885, colleges in 16 states had established by impact factors derived from the SCI agricultural experiment stations with the Journal citation Reports @ (JCR @).Impact USDA.~ factors reflect the average number of cita- At about this time, agronomy came to be tions per published “source item” during a recognized as a separate science concentrat- two-yew period. Source items include re- ing specifically on crop and soil manage- search articles, review articles, and technical ment. In 1908, the American Society of notes, but not editorials, news reports, obit- Agronomy was established. With more than uaries, or other items that are fully indexed 12,000 members, it is presently the largest in SC[. For simplicity’s sake, source items professional society of agronomists in the will be referred to as articles. Thus, 1989 world. Agronomy today is a muhidiscipli- impact factors are calculated by dividing nary field that draws on, and contributes to, 1989 citations to a journal’s 1988 and 1987 the methods and theories of a wide variety articles by the totaf number of articles it of specialties as they apply to soil and plant published in these two years. management. These include, but are not Then, we will treat the 66 core journals as limited to, biochemistry, biotechnology, bot- if they composed one large “Macrojoumal any, chemistry, genetics, microbiology, pa- of Agriculture.” This allows us to identify thology, physics, and physiology.c the joumafs it cited most frequently and those by which it was most cited. Surveying the Lay of the Land This is followed by a list of the most-cited of Agricultural Research core journal articles to give a perspective on classic research topics examined by agrono- In this essay, we will follow the pattern mists and soil scientists. In addition, articles established in our continuing series of jour- in non-core journals that were most-cited by I Fgure 1: Impact factor trends, 1985-1989 JCR ‘, for Americm %ciet y of Agronom y (ASA )journals. core agriculture joumat set, and all JCR journals, 1.6 .ICR Mean _./. -.-.-”” 1.5 JCR Mean .—. —. —. —. —._. ______.-. -.-”-” 1.4 i 1.3 Agronomy J ---- ——. - -_ 1.2 1 \ ..-— — —— -- SOII SCI SW Am J

ASA F&Jan

Agronomy J core set!4s!2? Crop SCI 0.5 0.4 0.3 0.2 0.1

0 I I I I I I 1985 1986 1987 1988 1989 YEARS

458 the core agriculture journals am presented. number of 1989 citations to each journal’s Another perspective on specialty mess 1988 and 1987 articles as well as the num- within agricultural research is provided by ber of articles each published in these years. examining the 1989 research fronts that in- Soil Biology and Biochemistry, published cluded the greatest number of core journal by Pergamon, Exeter, UK, has the highest articles. impact factor—1.3 1. That is, it published 283 source items in 1988 and 1987 and re- Core Agriculture/Soil Science ceived 371 citations in 1989. The American Journals, 1989 SCZJCR Chemical Society’s Journal of Agricultural and Food Chemistry is second with art im- Table 1 presents the 66 agriculture and pact factor of 1.20, followed by Soi/ Science soil science journals covered in the 1989 Society of America Journal at 1.18. Hilgar- SC1, arranged by publisher and showing the dia, published by the University of Califor- year each was launched and its 1989 impact nia, Oakland, ranks fourth with an impact of factor. The oldest is Journal of Agronomy 1.06, followed by Elsevier Applied and Crop Scienc+2itschr#t fur Acker- Science’s Pesticide Science and Academic und Pjlanzenbau, which began in 1853 and Press’ Advances in Agronomy with virtually is published by Verlag Paul Parey, Berlin, identical impacts of 1.02 and 1.00, respec- Germany. Next in age are Journal of Agri- tively. cultural Science, published by Cambridge The mean impact factor for the 66 core University Press, UK (1905); the American agriculture journals as a group was 0,62.10 Society of Agricultural Engineers’ Transac- comparison, the mean impact for all 4,500 tions and ASA’S Agronomy Journal, both of journals covered in the 1989 .lCR was 1.57. which were launched in 1907; and the Jour- Of course, we should not make tw much nal of Economic Entomology (1908), pub- of these specific rankings since the differ- lished by the Entomological Society of ence separating some of these journals America. amounts to no more than one-hundredth of a The most recently published are Biology point. Although quantitative indicators are and Fertility of Soils (1985), Springer Ver- useful, one must be careful not to split hairs lag, New York; Agriculture Ecosystems & among journals that differ by only 0.01 or Environment (1983), Elsevier Science, Am- 0.05 points on impact or other factors. sterdam, The Netherlands; Crop Protection It also is more illuminating to consider (1982), Butterworth-Heinemaorr, Guildford, trends over several years rather than rank- UK; Biomass (198 1), Elsevier Applied Sci- ings in a single year. Figure 1 shows a graph ence, Barking, UK; and Soil & Tillage Re- prepared for my presentation at the ASA an- search (1980), Elsevier Science. nual meeting. It illustrates impact factor Of the journals in Table 1, 19 are pub- trends during a five-year pericd from 1985 lished in the US, including art English trans- to 1989—for each ASA journal, for all ASA lation of Soviet Soil Science published by journals, and for the core set of 66 agricul- Wiley, New York; 16 are from the UK, 5 of ture journals. It also gives the mean for all which are published by ElsevieC 10 are 4,500 journals covered in the JCR. published in The Netherlands (6 by Elsev- In 1985, Agronomy Journal had the high- ier); followed by Germany with 5; Australia est impact of the ASA journals at 1.2, well and Japan with 4 each, Canada, New Zea- above the ASA mean of 0.9 and the core set land, and Sweden with 2 each and France mean of 0.8. But by 1989, its impact had and Italy with 1 each, slipped to 0.7, slightly below the ASA mean of 0.8, but still higher than the core set mean Highest Impact Core Journals of 0.6. The Soil Science Socie~ of America Iournal slightly improved its impact factor Table 2 lists 32 journals with a 1989 im- from 1.1 in 1985 to 1.2 in 1989, while Crop pact factor of at least 0.50 and shows the Science maintained its impact at 0.6 with

459 Tabfe 3: The Xl journak most cited by the cure agriculture journak, 1989 SCI ‘$. Asterisks (*) indicate core Journals. A=atations from cure journals. B=citations from all joumafs, C=seff-citations. D=percent of total citations that are core-journal citations (A/B ). E+rcent of total citatkms that are self-citations (self-citing rate, C/13). F=pment of com-joumd citations hat are self-citations (C/A). G=1989 impact factor. H= 1989 immediacy index, I=total 1989 source items,

A B c D E F GH I *SoiI Sci. SW. Amer. J. 4,833 7.204 1,623 67.1 22.5 33,6 1.19 0.26 330 *Agron, J. 2,913 4,364 6a9 668 15.8 23,7 0,71 0.21 173 *CrOp Sci. 2,S91 4,709 1,320 55.0 28,0 50.9 0,61 0.16 427 *SOil Sci. 1,740 2,902 212 60.0 7.3 12,2 0.65 0.16 116 *J. E.con. Entomol. 1,663 4,237 1,201 39.2 28.3 72.2 0.74 0.14 326 *Plant Soil 1,628 3,249 550 50.1 16.9 33,8 0.69 0.14 w *Soil Biol. Biochem. I ,609 2,673 632 60.2 23.6 39.3 1,31 0,27 171 *T ASAE 1,498 1,986 837 75.4 42.1 55.9 0.37 0.08 277 *Agr. Biol. Cbem, Tokyo .463 6.416 1,267 22.8 19.7 86,6 0.86 0.32 625 *J. Agr. Fmd Cbem. ,298 5,999 698 21.6 11.6 53.8 1.20 0.20 340 Plant Physiol. ,124 20,333 5.5 ...... 2.84 0.42 754 *Weed Sci. ,027 1,625 642 63.2 39.5 62.5 0.59 0. [6 116 J. Biol. Chem. 984 183.385 . . . 0.5 . . . 6.64 0.97 3,292 *J. Soil Sci, 984 I ,451 234 67.8 16.1 23.8 0.95 0.27 77 *Aust. J. A~. Kes. 937 1.885 332 49.7 17.6 35,4 0.74 0.30 120 *J. Agr.Sci, 918 2,359 187 38.9 7.9 20,4 0.49 0.06 107 J. Environ, Qual. 803 1,867 . . . 43.0 . . . 1.20 0.26 94 *J, Sci. Focal Agr. 773 2,835 265 27.3 9,3 34,3 0.68 0.19 182 Nature 752 178.265 0.4 ...... 18.05 4.21 I,045 Phytopathobgy 744 7,19U . . . 10.3 1.51 0.27 236 Appl. Envmun, Micmbiol. 688 12,251 . . . 5.6 2.43 0.32 584 *Can. J, Soil Sci. 688 97 I 206 70.9 21.2 29.9 0.73 0.10 90 Science 655 117,063 0.6 18.26 3.61 829 Agronomy 587 707 83.0 . . . !WA NIA 0 J. Fcmd Sci. 534 5,68 9,4 0,80 0.12 427 *Aust. J. Exp. Agr, 51[ 726 19 70.4 26.3 37.4 0.40 0.14 104 *Aust. J. Soil Res, 510 658 69 77.5 25.7 33,1 0.84 0.41 63 Water Resow, Res. 477 4,354 . . 11.0 1.73 0.39 236 Environ. Entomol. 466 2,626 . . 17.7 ...... 0.73 0.16 186 ‘fkor. App[. Ckmet, 463 3,213 . . 14.4 ...... 1.62 0.16 263 Biochim. BIophys, Acts 455 65,848 . . 0.7 ...... 2.26 0.34 1,899 *COrnnum. Soil Sci. Plant And 439 7.30 53 m. 1 21.0 34.9 0.47 0.05 134 Am. Appl. Biol. 436 1,987 . . 21.9 0.49 0.17 104 Can, J. Plant Sci. 436 1,357 32,1 0.44 0.12 162 *Advan. Agron, 434 681 26 63.7 3.8 6.0 1.(KI 0.00 9 Phymcbemisby 417 lo,fx12 4,2 ...... 1.10 (),20 808 New Phytol. 416 4,110 10,1 ...... 1.46 0,31 2(I3 *Euphytica 409 1,02] I93 40.1 18.9 47,2 0.39 0.13 168 J. him. Sci. 405 8,348 4.9 . . . 1.36 0,30 3%3 *Agr. Forest Meteoml. 393 736 244 53.4 33,2 62.1 0.63 0.04 102 Physiol, Plant- 378 6,186 6.1 . . . 1.76 0.28 273 Can. J. Bet, 363 5,867 6,2 . . . 0.81 0.20 418 Am, Bet 360 2,722 13,2 . . . 0.71 0.17 163 ‘N. Z. J. Agr, Rex. 351 694 I39 51.4 20.0 38.9 0.43 ().19 62 ‘Pestic. Sci. 345 928 128 37.2 13.8 37.1 1.02 0.11 104 Anal, Chem. 344 27,103 I.3 3.64 0.63 584 J. Exp. Bet. 336 3,356 . . . 10.0 . . . 1.36 0,25 114 Biocbem. J. 334 44,524 0.8 3.63 0.58 1,0% Pmt. Nat. Acad. Sci. USA 330 180,W 0.2 ...... 9.97 1.34 2,090 *Gec&nna 328 567 46 57.8 8.1 14,0 0.56 0.05 39

460 .-

ordy slight fluctuation during this period. amount to about 5 percent of all the citations By comparison, the mean impact for the en- these 50 journals receivti in 1989. tire core set declined from 0.8 in 1985 to 0.6 Of the 50 journals most cited by the in 1989. Macrojournal of Agriculture, 25 are them- selves core journals (indicated by asterisks). The top 10 journals are all core journals, The Macrojourrral of Agriculture and the first 3 are ASA publications. The Soil Science Society of America Journal As stated earlier, we treat the 66 core jour- leads with 4,833 citations from the core, fol- nals as if they comprise a single “Macro- lowed by Agronomy Journal (2,913 core ci- joumal of Agriculture:’ to see what it cites tations) and Crop Science (2,59 1). and, conversely, what cites it. In 1989, the Plant Physiology is the leading non-core core set published 6,608 articles. This journal most cited by the h4acrojournal of amounts to 1.30 percent of the 507,401 strti- Agriculture, with 1,124 core citations in cles included in the JCR that year. These 1989, representing 5.5 percent of the more articles gave out 122,453 citations to 22,153 than 20,00Q citations this journal received journals, or 1.46 percent of the 8.4 million from all publications in the JCR that year. citations in the 1989 JCR database. Two leading multidisciplinary joumals— Just four core journals account for 26 per- Narure and Science—also are listed, as is cent of the 6,608 articles published by the the Proceedings of the NaIiona[ Academy of core in 1989. They are Agricultural and Bi- Sciences of the United States of America ological Chemist~Tokyo (625 articles), (PNAS). In these cases, core citations Crop Science (427), Journal of Agricultural amount to less than 0.7 percent of total cita- and Food Chemistiy (340), and Soil Science tions each journal received in 1989. This Society of America Journal (330). And, 11 indicates that the core is selectively citing journals account for more than 50 percent of that fraction of the literature relevant to all artic[es published by the core in 1989. agronomy and soil science published in Na- This is merely another illustration of the ture, Science, and PNAS. These have tended well-known Bradford and Zipf distributions to appear consistently among our lists of and various other statistical patterns that journals most cited by various specialties, have been reviewed previously.7.8 which reflects each journal’s key position in scientific communication across many dis- Which Journals the Core Cited ciplines. To a lesser extent, the same is true of large journals that are prominent in a par- Table 3 lists the 50 journals most cited by ticular field, such as chemistry or the life the core, in descending order of total core sciences— Journal of Biological Chemistry, citations received, shown in column A. It Biochemical Journal, Analytical Chemistry, also gives data on total citations received and so on. from all journals (column B); the number of times each joumrd cited itself, or self-cita- Which Journals Cited the tions (C); the respective percentages of Macrojournal of Agriculture core-to-total (D), self-to-total (E), and self- to-core (F) citations: 1989 impact factors Table 4 lists, again in descending order, (G); 1989 immediacy indexes (H), or the the 50 journals that most frequently cited average number of times a journal’s 1989 the 66 core agriculture journals in 1989. The articles were cited in 1989; and the number core group received more than 39,000 cita- of source items published in 1989 (I). tions from these 50 journals, amounting to These journals received nearly 43,60U ci- 53.5 percent of all citations received by the tations from the core group in 1989, which core in 1989. They also represent 16.4 per- represents 35.6 percent of all citations by cent of all citations by the 50 journals listed the core that year. The core citations also here that year.

461 Tabk 4: The 50 journafs tJtat most frequently cited thecoreagriculture journafs, 1989 SCI ~. Asterisks (*) indicate cm-ejournals. A=citations to core jmunals. B=citadons to at] journals. C=self-citations. D=percent of total citations that are com-@umal citations (.&B), E=percent of total citations that are self-citations (self&ted rate. C/B). F=mrcent of core-journal citaticms that are self-citations (C/A). G= 1989 imtmt factor. H= 1989 immediacy index. [=total I9f19source items,

A B c D E FG H 1 *Soil Sci. SW. Amer. J. 3,539 7,566 1,623 46.8 21.5 45,9 1.19 (),26 334 *CrOp Sci. 2,232 5,fj23 1,320 39.7 23.5 59.1 0.61 0.16 427 *Planl Soil 1,937 6,491 550 29.8 8.5 28.4 0.69 0.14 309 *Agron. J. 1,542 3,259 689 47.3 21,1 44.7 0.71 0.21 173 *J. Emn. Entomcd. 1,52 I 5,466 1,201 27.8 22.0 79.0 0.74 0.14 326 *Soil Bio LBiochem. I,454 3,882 632 37,5 16.3 43.5 1.31 0.27 171 *Agr. Biol. Chem, Tokyo 1,379 9,394 1,267 14,7 13.5 91.9 0.86 0.32 625 *T. ASAE 1,344 4,049 837 33.2 20,7 62.3 0.37 0.08 277 *J. Agr. Fcmd Chem. 1,194 6,868 698 17.4 10.2 58.5 1.20 0,20 340 *COmrnun, Soil Sci, Plant Anal. 1,084 2,271 153 47,7 6.7 14.1 0.47 0.05 I34 *BIoI. Fat. Soils 1,021 2,796 76 36.5 2.7 7,4 0.79 0.13 Ill *Can. J. Soil Sci. 960 1,831 206 52.4 11.3 21.5 0.73 0.10 90 *SOil Sci. 960 2,150 212 44,7 9.9 22.1 0.65 0.16 116 *Weed Sci. 929 2,368 642 39.2 27. I 69.1 0.59 0.16 116 *J. Soil Sci. 914 1,923 234 47.5 12.2 25.6 0.95 0.27 77 “Amt. J. Agr. Res. 891 2,780 332 32.1 11.9 37.3 0.74 0.30 120 ACS SYIIIP.Ser. 809 25,203 3.2 . . . . . O.!W 0.17 869 J. Environ. Qual. 750 2.503 . . . 30.0 1.20 0.26 94 *Soil fill. Res. 73$ I,322 98 55.8 7.4 13.3 0.53 0.13 63 Can. J. Plant Sci. 680 2,682 25.4 . . . 0.44 0.12 162 *Aust. J. Soil Res. 672 I,395 169 4&2 12.1 25, I 0.s4 0.41 63 Appl. Environ. Microbiol 623 15,482 . . . 4.0 2.43 0.32 584 *Fteld Crop Res. 607 1,321 102 46.0 7.7 16.8 0.63 0.35 69 J, Food Sci. 593 8.658 6.8 . . . 0.80 0.12 427 *Euphytica 573 2,847 193 20.I 6.8 33.7 0.39 0.13 16% *Advan. Agmm 555 1,517 26 36.6 1.7 4.7 1.(Q 0.03 9 *J. Sci. Food Agr. 533 3,500 265 15.2 7.6 49.7 0,68 0.19 182 *J. Agr. Sci. 524 1,900 187 27.6 9.8 35.7 0.49 0.06 107 *Agr, Forest Meteoml. 513 2,58 I 244 19,9 9.5 47,6 0.63 0.04 102 Htirtscience 507 4,602 11,0 0.42 0.07 403 *PeSic. Sci. 497 2.512 19.8 5.1 25.8 I.02 0.11 104 Them AppL Cienet. 477 6,087 7.8 . . . 1.62 0.16 263 *Aust. J. EXP. Agr. 475 1,457 191 32.6 13.1 4(I2 0.40 0.14 104 J. him. Sci, 454 10.066 4.5 1.36 0.30 390 Envitun. Emomol. 436 3.859 11.3 . . . 0.73 0,16 186 J. Plant. Nutr. 431 1,661 25.9 . . . 0.51 0.10 84 Plant Physiol. 42I I8,944 2.2 2.84 0.42 754 Water Resour. Res. 42I 6.046 7.0 1.73 0.39 236 Sci. TotaJ Envir. 405 6,433 . . . 6.3 . . . 0.68 0.18 307 Z. Pt3am Bodenk. 398 1,395 28.5 . . . 0.69 0.23 73 J. Amer. Sac. Hort, Sci. 396 4,W44 9.7 . . . 0.69 0.15 211 Pestic. Biochem. Physiol. 392 2,424 16.2 1.34 0.16 95 *J. Agmn. Crop. Sci. 36I 1,376 13 26.2 0.9 3.6 0.16 0.01 89 *N, Z. J. Agr. Ras. 353 1,07 I I39 33.0 13.0 39.4 0.43 0.19 62 *Soil SC]. Plant Nutr 352 979 113 36.0 11.5 32.1 0.53 o,~6 M J. Chem. Ed. 334 5,246 6.4 1.46 0.26 213 Can. J. Forest Res. 326 5,750 5.7 . . . 0.66 0.13 223 J. Dairy Sci, 319 9,325 3.4 1.25 0.18 360 *J. Agr. Eng. Res. 313 1,109 94 28.2 8.4 30.0 0.23 0.04 74 New F%ytol. 308 6,057 5. I . . . 1.46 0.31 2W

462 Table 5: Tbe 20 must-cited articles from the core agriculture journals, 1945 -19S8 SCI o. Ardcles we fisted in alphabetic order by first author. A=1945- 1988 citatkm.s. B=1989 citations. An asterisk (*) indicates tfutt the paper was the subjmt of a Ciraion C/assic @ cummentmy. The issue, year, and edition of CC@ in which the commentary ap~~d fOflOwtie ~bliO~Phic refe~n= SC~/SSC~o m-h-front numb for1989alsofollowtherefereme.

AB Bibttographic Data 1,155 68 Abbott W S. A method of computing the effectiverwss of an insecticide. J. Econ. Entomol. 18:265-7, 1925, 89-IX33I 534 47 *Bray R H & Kurtz LT. Determination of totaf, organic, and avaifable fomn.sof pbosphoms in soils. Soil Sri. 59:3945, 1945. (29iS7/AB&ES) 89-3 IfXt 356 12 Cbmrg S C & Jackson M L. Fractionation of wil phosphoms. Soi/ Sci. 84:13344, 1957.89-2941 353 13 *Dmrafd C M. Competition among crop and pasture plants. Advan, Agron. 15:1-1I8, 1963. (23/’79/AB&ES) 89-47$4 431 28 *Eberhart S A & Russell WA. Stabifity parametersfor compting varieties, Crop SC1.636-40, 1966. (19/79/AB&ES) 89-3016 583 51 *Fehr W R, Cavinesa C E, Burmoad D T & Pennhrgton J S. Stage of &velopment descriptions for soybams, G/ycine max (L.) Merrill, Crop Sri, 1I :929-31, 1971. (12f12/AB&ES) 89-1514 528 32 Finlay K W & WMnson G N. The anatysis of adaption in a plant-breedhrg pmgmmme. Aus[. J. Agr. E’m. 14:742-54, 1963, 89-3016 461 26 Hardy R W F, Burns R C & Holsterr R D, Applicaticms of the acetylene+thylcne assay for measurement of nitrogen fmarion. Soil Bio/. Biorhem. 5:47-81, 1973. 482 22 ●H@e J E. &h ydmted feds: chemisby of browning reactions in model systems. J. Agr. Food Chem. 1:92843, 1953. (12f79/AB&ES) 89-0284 698 26 Hyd4n S. A Nrbidhm+ric medmd for the determination of higher polyethylene glyculs in biological materials. L.antbrrskshoegsk. Arm 22:139-45, 1955. (Superseded titfe of Sw,ed. J. Agr. Res.) 4tYl 12 Kilmer V J & Alexrmder L T. Methods of making mechanical analyses of soils. Sod Sri. 68:15-24, 1949, 421 34 Lindssy W L & NorveU W A. Development of a DTPA soil test for zinc, iron, manganese, and copper, Soil Sci, Sot. Amer. J, 42:421-8.1978. 430 13 Martin J P. Use of acid, mse bengal, and streptomycin in the plate method for estimating soif timgi, Soil Sri, 69:215-32, 1950. 344 38 *Pomamperuma F N. The chemistry of submerged soifs, Adwm. Agron. 2429-96, 1972. (22/83/AB&ES) 403 21 Sbom?y H H & Hate R L. Mass-rearing of the larvae of nine noctuid s~ies on a simple artificial medium. J. Ecrm. Entornd, 58:5224. 1%5. 589 24 Swain T & HiUis WE. The phenolic cmrstitucnts of prunus domeslicus. I.—me quantitative analysis of phenofic mnstitwmts. J. Sci. Food Agr. 10:63-8, 1959.89-3208 448 20 Takatauki A, Kohno K & Tamura G. fnhibhion of biosynthesis of plyisopreml sugars in chick embtyo microsomes by tunicamycin, Agr. Bio/. Chem, Tokyo 39:2089-91, 1975, 752 52 Wattdey A & Black 1 A. An examination of the Degtjareff methud for determining soil organic matter. and a proposed modification of the chromic acid titration method. Soil Sci. 37:29-38, 1934. 356 30 Watam+he F S & Oisen S R. Test of an ascortic acid methud for determining phosphems in water and NaHCOI extracts from soil, Soi/ Sci. .SOC.Proc. 29:677-8, 1%5. 502 74 *Zadoks J C, Cbang T T & Korrrak C F. A decimal code for the growth stages of meats. WeedRes. 14:415-21, 1974. (41/S5/AB&ES) 894672

Thirty journals in Table 4 are core jotsr- Plant and Soil, published by Khswer, nals, as indicated by asterisks. Again, the Dordrecht, The Netherlands, ranks third ASA journals dominate in terms of the num- with 1,937 citations to the core, and the En- ber of times they cited the core. Of the top tomological Society of America’s Jourrtd of five journals that most frequently cited the Economic Entomology is fifth with more Macrojournal of Agriculture, three are pub- than 1,500 citations. (Another ASA joumrd, lished by the ASA--Soil Science Society of the Journal of Erwironrnental Quality, is America Journal leads with more than among the top 20 with 750 citations to the 3,500 citations to the core group in 1989, core. ) followed by Crop Science (2,232 citations Comparing Tables 3 and 4, 9 journals ap- to the core), and Agronomy Journal ( 1,542). pear among the top 10 in both lists—the 5

463 Tabk 6 Articles pubtkhed in non-cure journafs cfted at least 25 times by core agriculture journata+ 1989 SCI’. Articles are listed in alphabetic order by first author. A= 1989 citaduns from core paps. B=total 1945-1988 SC/ citations. C. 1989 .SCf citations. An asterisk (*) indicates the paper was the subject of a Cmrion C/amic @ commen- tw. The Issue, yew, and editim of CC m in which the ccnmmnrary appeared folfow the bibliogmphic reference. SC//SSC/ @research-front numbem for 1989 also foltow the reference.

A BC Bibfiugrapbic Data 45 24,366 4,826 Bradford M M. A rapid and sensitive methud for tbe quantitatkm of micmgram quantities of protein utilizing the principle of proteindye binding. And Biochem. 72:248-54, 1976.89-3034 45 17.510 510 Davis B J. Disc elextrophuresis---U, Method and application to human serum prc+eins. Ann. NY Acad. Sri. 121:404-27, 1964.89-4581 33 9,741 573 DuBois M, GiItes K.& Hamittnn J L Rebers P A & Smith F. Colorimmic metbud for determination of sugar and relakd substances. Anal. Chem. 28:350-6, 1956. 57 8,985 413 ●DuncarI D B. Multiple ran8e and multiple F tests. 8ionzerrics 11:142, 1955. (4/77) 29 930 59 Hardy R W F, Hokten R D, Jackson E K & Burns R C. The acetyleneabylene assay for N2 fmatiom Iafxwatory und field evaluation. P/ant Physio/. 43:1185-207, 1968. 122 59,759 9,56 I Laemfll U K. Cleavage of structural proteins durin8 tfte assembly of the head of bacteriophage T4. Namre 227:68fL5, 1970.89-3034 I42 187,652 9,435 *Lowry O H, Rusebruugb N J, Farr A L & Ranrfatl R J. Protein measurement with the Folin phenol reagent. J. Itio/. Chem. 193:265-75, 1951. ( 1/77) 46 5,880 760 ●Murasfdge T & Skoog F. A revisal medium for mpid growth and bioa.ssays with tobacco tissue cultures. Physio/. P/am. 15:473-97, 1%2. (43/78) 894032 59 2,052 158 ●Murphy J & Riley J P. A nmdif~d single sulution method for tfx determination of phosphate in natural waters. And Chim. Ac!a 27:31-6,1962. (12186/AB&ES) 27 787 82 Pfdltips J M & Hayman D S. Improved procedures for clearing nmrs and staining parswtic and vesiculw-arbuscular mycorrbizal fungi for rapid assessment of infection, Trans. Brir. Myco/. SW. 55: 158*1, 1970.89-3375 noted previously as well as Agricultural and the most-cited articles in the 1955-1986 Biological Chemistr.~Tok.vo, Journal of SC!.10 Agricultural and Food Chemistry, Soil Biol- Seven papers in Table 5 were the subject OgY d Biochemist, and Transactions of of Ci[ation Classic @ commentaries by the the ASAE. authors. They are indicated by asterisks, and the issue, year, and edition of Current Con- High Impact Articles tents @ (CC @) in which the commentaries in the Agricultural Sciences appeami follow the reference in parenthe- ses. Tables 5 and 6 present separate sets of As is frequently the case with Citation articles that have proven to b of wide inter- Classic commentaries, the authors offer in- est to agronomists and soil scientists. Table sights into subjects that range fw afield 5 lists the 20 most-cited articles from the from the specific researeh problem ad- core journals, based on the 1945-1988 SCI dressed in their papers. An example is the database. Table 6 shows 10 articles pub- commentary by John E. Hodge, Cereal Sci- lished in non-core journals that were cited at ence and Foods Laboratory, USDA, Peoria, least 25 times by the core in 1989. Illinois, on his 1953 Journal of Agricultural The most-cited core journal article in and Food Chemistry paper on the chemistry Table 5 is a 1925 Journal of Economic En- of browning reactions. 11He described how tomology article describing a method for a series of chance discoveries led him to calculating the effectiveness of an insecti- write the now classic paper, and observed: tide.g Authored by W.S. Abbott, USDA, “Today’s tightly organized research seems Washington, DC, it received 1,155 citations to leave little room for serendipity. Then [in in the 1945-1988 SCI and was cited 68 the 1950s], research was planned as it pro- times in 1989, indicating continued use of gresse~ dollar values were not preassessed. the method described. The paper also ap- Now, plarrs of work predominate, while peared in our previously published study of chance discoveries suffocate. How bench

464 Tabte Z Tbe 1989 SC1 @/SSCI @ research fronts that inctude at Ieasl 60 cithrg ducuments published in the core agrfcrrlture journals. A=munbsr of articl= fmm cnre agricult~e journals citing the core of each tlom. B=t@ai number of citing dncuments. C=rnral number of core dncumenrs,

Number Name A B c 89-0037 Msim pmtoplssts,plant-regeneration in (OWZUsafiva L.), stable tmnsfonna.tion, @ 669 al anti culture,-tic embryogenesis,andcaflusfmmntinn 89-0614 Growth of winter-what rcmts, leaf emergence, maize phrenology, ccarstsnt 121 267 39 temperatures, degreeday mndel, and dry-matter accumulation 890881 Soil nricmbist biomass, nitrogen minersfization, snd tmnsformstirrns nf 95 125 11 nnn-symbioticstly fixed N (5 89-1029 Ammmiavoladfization, hydrolysis of um, srmnsphericsampling,wetannular 112 271 36 denudwsystem,nitrogenlosses,pm’dculstenitrate,andcollectingefficiency 89-1087 Bradyrhizobiumjrponicum strains fornndufatinn,nitmgenawactivity,NZ 120 281 42 fixationin Tfrsi snybmns, and narrow-leafed lupin (Lupinus arrgusfolius L.) 89-1364 Acid sulfate snils, mnlybrfste sdsoqrrion, reductive dissnlutinn of gnetbite, 83 158 15 snlid-wlutinn interface, and aqueous sus~nsions 89-2184 Conservation tilfage, pnndy dmined Molfic @usquaff in nnrthwest Ohio, clay 69 110 15 soils, wheel traffic, nnd potential aUelnpattric characteristics 89-2679 Ponrly drained suit, conservation tiUage systems, Mojave desert region, nitrogen 105 117 13 lnsses, particulate nitrate, snd collection efficiency 89-3016 Seed yield stsbitity, recument selection, international resize trials, ost cultivam, 92 160 15 and envimnmentat sensitivity 89-3034 Micmtubule cross-linking pmrein, small syrra@c vesicles of rat-brain, snd 115 13,994 3 axntinin hcatizstinn 89-3124 Nimogen minemiiration, NM content nf wits, and chemolithotrophic nitritlcatinn 70 S3 4 in acid heathkmd humus 89-3375 Vesiculw-arbuscukar nricmrhizal hmei. hrceme rcmts in a cellulose-amended snil 68 IS9 19

scientists thrive upon serendipity is illus- but also biochemistry, botany, clinical medi- trated [in this commenta~].”lz cine, geochemistry, metallurgy, zoology, In several of these commentmies, the au- and many other fields. 15.16 thors account for the high impact of their Other papers listed include the supercited classic papers by noting the multidiscipli- classic by Oliver H. Lowry and colleagues, nary nature of agronomy and soil science. Washington University School of Medicine, For example, F.N. Ponnamperuma. Intern- St. Louis, Missouri, which has been cited ational Rice Research Institute, Los Baiios, more than 200,000 times since it was pub- Philippines, stated that his classic 1972 Ad- lished in the Journal of Biological Chemis- vances in Agrononty review article on the try in 1951.17,18In an earlier journal citation chemistry of submerged soils involved iden- study of botany, Brent Heath, York Univer- tifying and reviewing research in: biochem- sity, North York, Canada, explained that the istry; electrochemistry; physical, inorganic, Lowry method is used by plant scientists to and organic chemistry; thermodynamics; measure plant protein content in order to and bacteriology. 1S.1’$ defiie a standard against which other plant This point is reinforced by the list of pa- constituents may be measured-enzyme ac- pers in non-core journals most cited by the tivity per milligram of protein, for exam- Macrojournal of Agriculture shown in Table ple,1920 6. They are virtually a compendium of methods that are basic to all life and physi- Current Research Fronts cal sciences research. James Murphy and in the Agricultural Sciences John P. Riley, University of Liverpool, UK, noted that their 1962 Analytica Chinrica Table 7 presents 12 research fronts for Acts paper on determination of phosphate in 1989 that included at least El) citing articles natural waters has found applications not published in the core agriculture journals only in oceanography and water research, that year. The method used to identify and

465 map research fronts has been described in trification in acid heartland humus,” with detail previously.j 1.22Briefly explained, the 84.3 percent of its 83 citing articles having method takes the reference list of a paper appewed in the Macrojourna[ of Agricul- and pairs each of the citations with one an- ture. other. Our computer then searches for other papers that co-cite the same pairs of papers, Conclusion thereby creating a cluster of research linked by co-citation. The cited papers constitute As is customary in our series of journal the core of the cluster while the citing pa- citation studies, we conclude by identifying pers make up the current research front. The a smafl number of key publications that ap- names of these research fronts are automati- pear prominently among the various citation cally derived from the word pairs and rankings discussed here. Of the 66 core ag- phrases in the titles of the citing papers, riculture joumafs included in this study, 9 much as we do with Key Words Plus ‘“.I~,Ib ranked among the top 15 in terms of impact, The most active agriculture research front the number citations received by the core, in Table 7, in terms of the number of citing and the number of citations to the core. artic Ies from core journals, is entitled They are Agricultural and Biological “Growth of winter-wheat roots, leaf emer- Chemistry----Tokyo, Agronomy Journal, Aus- gence, maize phenology, constant tempera- tralian Journal of Agricultural Research, ture, degree-day model, and dry-matter ac- Journal of Agricultural and Food Chemis- cumulation” (#89-061 4). It includes 121 tq, Journal of Economic Entomology, Jour- citing papers from the Macrojournal of nal of Soil Science, Plant and Soil, Soil Bi- Agricu//ure, which represent 45.3 percent of ology & Biochemistry, and Soil Science all 267 citing papers in this research Society of America Journal. front. These papers cited 39 core docu- In addition, 2 journals ranked among the ments. Next is research front #89-1087, top 15 in terms of impact and citations to “Bradyrhiwbium japonicum strains for mod- the core, but not citations from the core. ulation, nitrogenase activity, N2 fixation in They are Biology and Fertility of Soils and Thai soybeans, and narrow-leafed lupin Canadian Journal of Soil Science. (Lupinus angus@lius L.),” with 120 citing Of course, as in most specialties, agrono- articles from the Afucrojoar-nal of A,qricul- mists and soil scientists also rely on large ture. multidisciplinary journals, such as Nature, The research front in which core agricul- Science, and PNAS, to communicate and ture articles are most dominant, in terms of learn of important research in their special- their proportionate share of total citing arti- ties. As noted earlier, other more specialized cles, is #89-2679, “Pcmrly drained soil, con- journals covering broad fields that are rele- servation tillage systems, Mojave Desert re- vant to the agricultural sciences, such as gion, nitrogen losses, particulate nitrate, and biochemistry, are also important. collection efficiency.” Of the 117 citing pa- *..** pers in it, 105 (89.7 percent) were published in core agriculture journals in 1989. Next is My thanks to Al Welljams-Dorof and Eric #89-3 124, “Nitrogen mineralization, N 15 Thurschwell for their help in the prepara- content of soils, and chemolithotrophic vi- tion of this essay. Qlmlsl

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