Chapter 1

The Effectiveness of American Society of Agronomy Journals:

A Citationist�s Perspective

Eugene Garfield
Institute for Scientific Information
Philadelphia, Pennsylvania

 

ABSTRACT

Citation data for 66 agronomic and soil science journals indexed in the 1989 Science Citation Index (SCI) are examined to determine how publications of the American Society of Agronomy compare with others in the field. For these �core� journals, rankings by number of articles, citations, and impact factors are presented. The journals are then treated as if they comprised a single �Macrojournal of Agronomy� to see what publications it cited and what it was cited by. Highest impact articles and most active research fronts in agronomy and the soil sciences are also presented. Based on these data, 11 journals are identified as occupying a prominent position in the field.

It is a pleasure and an honor to be here today, and to address this group on the effectiveness of American Society of Agronomy (ASA) journals. There are usually two reasons why I am invited to speak before professional societies or groups of journal editors and publishers; they want to know if their journals are strong or weak. When Bob Sojka and Hank Mayland invited me to this meeting (R.E. Sojka and H.F. Mayland, 1989, personal communication), they were pretty explicit about their motives. They wanted to know if the ASA journals are having a real impact or, to quote Bob and Hank, �are we only talking to ourselves?� In particular, they asked whether �citation analysis bears out the ASA�s perceptions that our journals are the premier journals of agronomic and resource management,� (R.E. Sojka and H.F. Mayland, 1989, personal communication).

I am happy to say that the answer to this question is yes. As will be illustrated in this presentation, the ASA journals indexed in the Institute for Scientific Information�s (ISI) 1989 edition of the SCI appear to be among the most �influential� in the field of agronomy and soil science by various citation indicators.
 
 
 

CITATION DATA FOR JOURNAL ANALYSIS

Our series of journal citation studies, which now number over 50, are derived from ISI�s SCI database, a multidisciplinary and comprehensive index to the leading international research literature. The SCI is distinct from other major secondary information services in several ways. For example, the SCI reflects the interdisciplinary nature of research by covering virtually all scientific disciplines rather than being limited to a single one.

Also, the SCI provides complete cover-to-cover indexing of every type of item published in a journal�not just research articles, reviews, and notes but also letters, er rata, corrections and retractions, editorials, and so on. The ISI studies have indicated that many of these so-called �source items� can be cited as often as, and some-times even more often than research articles (1).

This brings us to the SCI�s most unique distinction� that it fully indexes not only every source item but also all the references they cite. Citations forge links between current citing papers and earlier cited works. On a microlevel, these links are highly useful for information retrieval. They allow researchers to move backward and forward in time to identify publications relevant to their specific interest.

On a macrolevel, citations define broad relationships in the literature as a whole. Increasingly, these data are being used for descriptive and evaluative purposes to determine, for example, how journals or institutions or nations compare in terms of volume and impact of pub-lications; what are the hottest articles and research fronts, and so on.

In this presentation, we�ll survey the �lay of the land� in the agronomic and soil science literature and identify the most � �fruitful� journals. We�ll start with a group of 66 agronomic/soil science journals indexed in the 1989 SCI, and present various rankings by articles, citations, and impact. Then we�ll treat the 66 agronomic/soil journals as if they comprised one large Macrojournal of Agronomy. This will allow us to identify the journals it cited most frequently and those it was most cited by. We�ll also present the specialty areas in which the ASA journals dominate, as well as identify their most-cited articles.
 
 

CORE JOURNALS OF AGRONOMY AND SOIL SCIENCE

Table 1-1 lists 66 agronomic and soil science journals covered in the Journal Citation Reports (JCR) volumes of the 1989 SCI, in alphabetic order by publisher and showing their first years of publication. The oldest is Journal of Agronomy and Crop Science/Zeitschrift für Acker- und Pflanzenbau, which was launched in 1853. Others are: Journal of Agricultural Science (1905); Transactions of the ASAE (American Society of Agricultural Engineers) and the ASA�s Agronomy Journal (both 1907); and the Journal of Economic Entomology (1908).

The most recent journals are: Biology and Fertility of Soils (1985), Agriculture Ecosystems and Environment (1983), Crop Protection (1982), Biomass (1981), and Soil and Tillage Research (1980).

Nineteen of these journals are published in the USA. These include an English translation of Soviet Soil Science. Sixteen are from the United Kingdom (UK), five of which are published by Elsevier. Ten are published in the Netherlands (six by Elsevier), followed by Germany with five. Australia and Japan each have four; Canada, New Zealand, and Sweden account for two each; and France and Italy each have one.

Three ASA journals are included here�the Agronomy Journal, Crop Science, and the Soil Science Society of America Journal. Another ASA journal, the Journal of Environmental Quality, is also covered in the SCI under the environmental science subject category. Data on this journal are presented later, but our focus will be on the agronomic and soil science journal set.

Now let�s see which of these agronomic and soil science journals are the most productive, in terms of the number of articles published in 1989.
 
 
 

LARGEST CORE JOURNALS OF AGRICULTURE AND THE SOIL SCIENCES

Table 1-2 shows 22 journals that published at least 100 research articles, review articles, and technical notes in 1989. (These source items will simply be referred to here as articles.) The three ASA journals are highlighted by daggers and rank among the top 10 journals by productivity  . The largest journal with 625 articles is Agriculturalal and Biological Chemistry, published by the Japan Society of Bioscience and Biotechnology, followed by the ASA�s Crop Science with 427.

It is interesting to note that the 66 agronomic and soil science journals published a total of 6608 articles in 1989. The first four journals in Table 1-2 account for 26% of the total, and the first 11 account for over 50% . This is merely another illustration of the well-known Bradford and Zipf distributions and various other statistical patterns (2). These patterns will also apply to the concentration   of citations in a small number of journals.
 
 
 
 
 
 
 

MOST-CITED CORE JOURNALS

Table 1-3 shows 16 agronomic and soil science journals that received at least 1000 citations in 1989. Again, the ASA journals are indicated by daggers, and they rank among the top five. The Soil Science Society of America Journal is first with 7204 citations, followed by Agricultural   and Biological Chemistry (6416) and the Journal of Agricultural and Food Chemistry (5999), published by the American Chemical Society.

All 66 agronomic and soil science journals received about 72 000 citations in 1989, and the first seven journals account for 50%.

I should point out that all of the journals in Table 1-3, with the exception of the Journal of Soil Science, also appeared in Table 1-2 listing the largest journals. This should not be surprising, since the largest journals tend also to be the most cited. This putative size advantage is one of the reasons why undifferentiated lists of citations should not solely be relied on as an indicator of im importance or influence.

To compensate for the size�citation relationship, ISI has developed the impact factor. This is a straightforward ratio that divides current year citations to articles pub-lished by a journal in the previous 2 yr by the total number of items published in that 2-yr period. Thus, the 1989 impact factor would reflect 1989 citations to articles published in 1988 and 1987.
 
 
 

HIGHEST IMPACT CORE JOURNALS

Table 1-4 lists 32 journals with 1989 impact factors of at least 0.50. Soil Biology and Biochemistry has the highest impact factor�i .31 . That is, it published 283 ar tides in 1988 and 1987, and they received 371 citations in 1989. The ASA journals are highlighted by daggers. The Journal of Agricultural and Food Chemistry is second with an impact of 1 .20, followed by Soil Science Society of America Journal at 1.18. The Agronomy Journal ranks 14th with an impact factor of 0.71 and Crop Science is 22rd with an impact of 0.61 . The mean impact factor of all 66 agronomic and soil science journals as a group was 0.52.

Of course, we should not make too much of these specific rankings since the difference separating some of these journals amounts to no more than one-hundredth of a point. While quantitative indicators are useful, one must be careful not to split hairs between journals that differ by only 0.01 or 0.05 points on impact or other factors.
 
 
 
 

It also is more illuminating to consider trends over several years rather than rankings in a single year. Figure 1-1 presents impact factor trends over the 5-yr period from 1985 to 1989. It includes data for each ASA jour-nal, for the ASA journals as a group, the core set of 66 agronomic and soil science journals, and the mean for all 4500 journals covered in the JCR.

You will note that in 1985 the Agronomy Journal had the highest impact of the ASA journals at 1 .2, well above the ASA mean of 0.9 and the core set mean of 0.8. But by 1989, its impact had slipped to 0.7, slightly below the ASA mean of 0.8, but still higher than the core set mean of 0.6. The Soil Science Society of America Journal slightly improved its impact factor from 1.1 in 1985 to 1 .2 in 1989, while Crop Science maintained its impact at 0.6 with only slight fluctuation during this period. In comparison  , the mean impact for the entire core set deteriorated from 0.8 in 1985 to 0.6 in 1989.
 
 
 
 
 

Figure 1-2 shows impact factor trends for the ASA journals compared against that of the core set. That is, the mean impact for the core agronomic and soil science journals has been set as a constant value of 1.0 for the 5-yr period. This allows us to see more clearly the per-formance of the ASA journals relative to the core set.

The Soil Science Society of America Journal shows the greatest gain relative to the core set mean. In 1985, its impact was 43% greater than the core mean, and by 1989 it was 90% greater. Crop Science also shows a gain, from 23% under the core set mean impact to equaling the core set impact in 1989. But the trend for the Agronomy Journal is the reverse�from having 58% greater impact than the core set in 1985 to 15% higher impact in 1989.

 Let�s now briefly compare the impact of another ASA publication, the Journal of Environmental Quality, to other ISI-indexed environmental science journals. Table 1-5 shows 24 environmental science journals that had an impact of at least 1 .00 in 1989. Environmental Science and Technology, published by the American Chemical Society, has the highest impact at 2.89. The Journal of Environmental Quality ranks 11th with an impact of 1.20. The average impact for all 60 environmental science journals indexed in the SCI that year was 1.02.
 
 
 

Figure 1-3 shows impact factor trends for the environmental science journals and the JCR as a whole. The Journal of Environmental Quality had an impact factor of 1 .5 in 1985, which dropped to 1.1 by 1987, increased to 1 .3 the following year before slipping slightly to 1.2 in 1989. The average impact for the 60 core environmental science journals declined slightly from 1.1 in 1985 to 1 .0 in 1989.

In Figure 1-4, the mean impact for the core will be set at 1.00 for the 5-yr period to compare the Journal of Environmental Quality against it. As you can see, the impact of the Journal of Environmental Quality in 1985 was 35% higher than that of the core set of 60 environmental science journals. By 1987 its impact equaled that of the core set, then increased to 30% greater in 1988 before winding up 18% higher in 1989.

 

 THE MACROJOURNAL OF AGRONOMY: WHAT IT CITES

As stated earlier, the 66 core agronomic and soil science journals can be treated as if they comprised a single Macrojournal of Agronomy to see what it cites and, conversely, what cites it. In 1989, the core set published 6608 articles, or 1 .3% of the more than 507 000 articles included in the JCR database that year. These articles cited 122 453 references to over 22 000 journals, representing 1.5% of the 8.4 million citations included in the JCR that year.

Table 1-6 shows the 25 journals that were most cited by the core, in descending order of total core citations received, shown in Column A. The table also gives data on total citations received from all journals (Column B); the number of times each journal cited itself, or self citations (Column C); the percentages of core-to-total (D), self-to-total (E), and self-to-core (F) citations; 1989 im pact factors (G); 1989 immediacy indexes (H), or the average number of times a journal�s 1989 articles were cited in 1989; and the number of source items published in 1989 (I).
 

Table 1-6. The 25 journals most cited by the core agriculture journals, 1989 SCI.
	A�	B	C	D	E	F	G	H	I
Soil Science Society of America Journal�	4 833	7 204	1 623	67.1	22.5	33.6	1.19	0.26	330
Agronomy Journal�	2 913	4 364	689	66.8	15.8	23.7	0.71	0.21	173
Crop Science�	2 591	4 709	1 320	55.0	28.0	50.9	0.61	0.16	427
Soil Science�	1 740	2 902	212	60.0	7.3	12.2	0.65	0.16	116
Journal of Economic Entomology�	1 663	4 237	1 201	39.2	28.3	72.2	0.74	0.14	326
Plant and Soil�	1 628	3 249	550	50.1	16.9	33.8	0.69	0.14	309
Soil Biology and Biochemistry�	1 609	2 673	632	60.2	23.6	39.3	1.31	0.27	171
Transactions of the American Society of Agricultural Engineers�	1 498	1 986	837	75.4	42.1	55.9	0.37	0.08	277
Agricultural and Biological Chemistry (Tokyo)�	1 463	6 416	1 267	22.8	19.7	86.6	0.86	0.32	625
Journal of Agricultural and Food Chemistry�	1 298	5 999	698	21.6	11.6	53.8	1.20	0.20	340
Plant Physiology	1 124	20 333	--	5.5	--	--	2.84	0.42	754
Weed Science�	1 027	1 625	642	63.2	39.5	62.5	0.59	0.16	116
Journal of Biological Chemistry	984	183 385	--	0.5	--	--	6.64	0.97	3 292
Journal of Soil Science�	984	1 451	234	67.8	16.1	23.8	0.95	0.27	77
Australian Journal of Agricultural Research�	937	1 885	332	49.7	17.6	35.4	0.74	0.30	120
Journal of Agricultural Science�	918	2359	187	38.9	7.9	20.4	0.49	0.06	107
Journal of Environmental Quality	803	1 867	--	43.0	--	--	1.20	0.26	94
Journal of the Science of Food and Agriculture�	773	2 835	265	27.3	9.3	34.3	0.68	0.19	182
Nature	752	178 265	--	0.4	--	--	18.06	4.21	1 045
Phytopathology	744	7 190	--	10.3	--	--	1.51	0.27	236
Applied Environmental Microbiology	688	12 251	--	5.6	--	--	2.43	0.32	584
Canadian Journal of Soil Science�	688	971	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	--	--	NA	NA	0
Journal of Food Science	534	5681	--	9.4	--	--	0.80	0.12	427
� Core journal.
� A = citations from core journals; B = citations from all journals; C = self-citations; D = percentage of total citations that are core� journal citations (A/B); E = percentage of total citations that are self-citations (self-citing rate, C/B); F = percentage of core�journal citations that are self-citations (C/A); G = 1989 impact factor; H = 1989 immediacy index; and I = total 1989 source items.

These 25 journals received 33 434 citations from the Macrojournal of Agronomy, or 27.3% of all citations it gave out in 1989. Sixteen of the journals listed are themselves core journals. They are indicated by daggers.

The three journals at the top of the list are all ASA publications�the Soil Science Society of America Journal is first with 4833 citations from the core followed by Agronomy Journal with 2913 and Crop Science with 2591 . The Journal of Environmental Quality also appears and ranks 17th on the list of journals most cited by the core.

Plant Physiology is the leading noncore journal cited most frequently by the Macrojournal of Agronomy. It received 1 124 core citations in 1989, which amounts to 5.5% of the more than 20 000 citations this journal received from all publications in the 1989 JCR database. Two leading multidisciplinary journals, Nature and Science, are also listed. For these journals, core citations represent less than 0.6% of total citations received. That is, the Macrojournal of Agronomy is selectively citing the fraction of the literature in Nature and Science that is relevant to its interests.

These and other leading multidisciplinary journals, such as the Proceedings of the National Academy of Sciences of the United States (PNAS), have consistently appeared in lists of journals most cited by various specialty journal sets. This reflects their key position in scientific communication across many disciplines.
 
 

WHAT CITES THE MACROJOURNAL OF AGRONOMY

Table 1-7 shows 25 journals that most frequently cited the core agronomic and soil science journals in 1989, in descending order of citations to the core. The Macrojournal of Agronomy received more than 73751 citations from 1425 journals in 1989. The 25 journals listed here cited the core 28946 times, accounting for 39.2% of total citations received by the core.
 
 

Table 1-7. The 25 journals that most frequently cited the core agriculture journals, 1989 SCI.
	A�	B	C	D	E	F	G	H								I
Soil Science Society of America Journal�	3 539	7 566	1 623	46.8	21.5	45.9	1.19	0.26								330
Crop Science�	2 232	5 623	1 320	39.7	23.5	59.1	0.61	0.16								427
Plant and Soil�	1 937	6 491	550	29.8	8.5	28.4	0.69	0.14								309
Agronomy Journal�	1 542	3 259	689	47.3	21.1	44.7	0.71	0.21								173
Journal ofEconomic Entomology�	1 521	5 466	1 201	27.8	22.0	79.0	0.74	0.14								326
Soil Biology and Biochernistry�	1 454	3 882	632	37.5	16.3	43.5	1.31	0.27								171
Agricultural and Biological Chemistry (Tokyo)�	1 379	9 394	1 267	14.7	13.5	91.9	0.86	0.32								625
Transactions of the American Society of Agricultural Engineers�	1 344	4 049	837	33.2	20.7	62.3	0.37	0.08								277
Journal of Agricultural and Food Chemistry�	1 194	6 868	698	17.4	10.2	58.5	1.20	0.20								340
Communications in Soil Science and Plant Analysis�	1 084	2 271	153	47.7	6.7	14.1	0.47	0.05								134
Biology and Fertility of Soils�	1 021	2 796	76	36.5	2.7	7.4	0.79	0.13								111
Canadian Journal of Soil Science�	960	1 831	206	52.4	1 1.3	21.5	0.73	0.10								90
Soil Science�	960	2 150	212	44.7	9.9	22.1	0.65	0.16								116
Weed Science�	929	2 368	642	39.2	27.1	69.1	0.59	0.16								116
Journal of Soil Science�	914	1923	234	47.5	12.2	25.6	0.95	0.27								77
Australian Journal of Agricultural Research�	891	2 780	332	32.1	1 1.9	37.3	0.74	0.30								120
ACS Symposium Series	809	25 203	-	3.2	-	-	0.90	0.17								869
Journal ofEnvironmental Quality	750	2 503	-	30.0	-	-	1.20	0.26								94
Soil and Tillage Research�	738	1 322	98	55.8	7.4	13.3	0.53	0.13								63
Canadian Journal of Plant Science	680	2 682	-	25.4	-	-	0.44	0.12								162
Australian Journal of Soil Research�	672	1 395	169	48.2	12.1	25.1	0.84	0.41								63
Applied Environmental Microbiology	623	15 482	-	4.0	-	-	2.43	0.32								584
Field Crops Research�	607	1 321	102	46.0	7.7	16.8	0.63	0.35								69
Journal of Food Science	593	8 658	-	6.8	-	-	0.80	0.12								427
Euphytica�	573	2 847	193	20.1	6.8	33.7	0.39	0.13								168
� Core journal.
� A = citations from core journals; B = citations from all journals; C = self-citations; D = percentage of total citations that are core-journal citations (A/B); E = percentage of total citations that are self-citations (self-cited rate, C/B); F = percentage of core-journal citations that are self-citations (C/A); G = 1989 impact factor; H = 1989 immediacy index; and I = total 1989 source items.

Twenty of the journals listed are core journals, and they are indicated by daggers. Again, the ASA journals dominate in terms of the number of times they cited the core. The Soil Science Society of America Journal is first with 3539 citations to the core, followed by Crop Science (2232 citations), Plant and Soil (published by Kiuwer, 1937 citations), and Agronomy Journal(1542). The Journal of Environmental Quality ranks 18th with 750 citations   to the core in 1989.

These data indicate that ASA publications are among the journals most closely tied to the agronomic and soil science literature. That is, ASA journals are among the heaviest �consumers� of agronomic and soil science research.

CITATION CLASSICS IN THE AGRONOMIC SCIENCES

Table 1-8 presents 20 articles from the core journals that were most cited in the 1945 to 1988 SCI database. These articles can be considered a sample representing topics that have proven to be of the widest interest or application in the field of agronomy and soil science. The most cited article is a 1925 Journal of Economic Entomology paper by W.S. Abbott, Bureau of Entomology, USDA. It described a method for calculating the effectiveness   of an insecticide and received 1155 citations during   the period 1945 to 1988. It was cited 68 times in 1989, indicating continued interest in the method described.

Four papers in Table 1-8 were published in ASA journals. Two appeared in Crop Science [see Eberhart & Russell (1966), and Fehr et al. (1971)], one in Soil Science Society of America Journal [Lindsay & Norvell (1978), and another in the Soil Science Society of America Proceedings [Watanabe & Olsen (1965)].

Seven papers have been the subject of Citation Classic commentaries written by the authors and published in Current Contents (CC). They are indicated by double daggers; and the issue, year, and edition of CC in which they appeared follow the reference in parentheses. These commentaries can be considered minibiographies of now classic research, in which the authors describe their work as well as the circumstances that led to its development and publication.
 
 

Tables 1-9 through 1-12

Tables 1-9 to 1-12 present the 20 most cited articles from the ASA journals included in this study, respectively, Agronomy Journal, Crop Science, Journal of Environmental Quality, and Soil Science Society of America Journal.
 
 
 

CURRENT RESEARCH FRONTS IN THE AGRONOMIC SCIENCES

Another perspective on current topics of particular interest in the agronomic sciences can be gained from ISI�s 1989 file of thousands of so-called research fronts. These are automatically generated by a method called cocitation cluster analysis. The method has been described in detail previously, and interested readers should refer to these publications (3 , 4).

Briefly put, the method takes the reference list of a paper and pairs each of the citations with one another. The computer then searches for other papers that cocite the same pairs of papers, thereby creating a cluster of research linked by cocitation. The cited papers constitute the core of the cluster while the citing papers make up the current research front. The names of the research fronts are automatically derived from the words and phrases in the titles of the citing papers.
 

Table 1-13 shows 12 1989 research fronts that included at least 60-citing articles from the core agronomic and soil science journals in this study. The most active research front, in terms of the number of citing articles from the Macrojournal of Agronomy, is no. 89-0614, �Growth of winter wheat roots, leaf emergence, maize phenology, constant temperatures, degree-day model, and dry-matter accumulation.� It includes 121-citing papers from core journals, which amount to 45.3% of all 267-citing papers in this research front. Of these, 33 were published in ASA journals. Next is no. 89-1087, �Bradyrhi zobium japonicum strains for nodulation, nitrogenase activity, N2 fixation in Thai soybean, and narrow-leafed lupin (Lupinus angustifolius L.),� with 120-citing articles from the core journals, of which 14 were ASA journal articles.

Table 1-14 identifies 31 1989 research fronts that included at least 10-citing articles published in ASA journals. These will indicate research areas in which the ASA is most active, again in terms of number of citing articles.
 
 
 
 

Table 1-15 provides another view on areas of special interest to ASA authors. It ranks research fronts by the proportionate share of total citing articles that were published in ASA journals.
 
 
 

CONCLUSIONS

Various citation data have been considered to deter-mine which agronomic and soil science journals indexed in the 1989 SCI can be said to occupy a prominant position   within the field. These include impact factors, citations received by the set of 66 core journals, and citations to the core. Eight of the sixty-six core journals ranked among the top 15 on all three of these indicators. They are: Agricultural and Biological Chemistry (Tokyo), Agronomy Journal, Australian Journal of Agricultural Research, Journal of A gricultural and Food Chemistry, Journal of Economic Entomology, Journal of Soil Science, Soil Biology and Biochemistry, and Soil Science Society of America Journal. In addition, two journals ranked among the top 15 in terms of impact factors and citations to the core, but not citations from the core. They are: Biology and Fertility of Soils and Canadian Journal of Soil Science.¹

Of course, agronomists and soil scientists also rely on large multidisciplinary journals such as Nature, Science and PNAS, as do researchers in other specialties. Other more specialized journals covering broad fields, such as biochemistry, that are relevant to the agronomic sciences are also important. Nevertheless, the 11 agronomic and soil science journals identified above may be considered the most prominent vehicles of research communication in this specialty. The ASA�s impression that its publications   are among the �premier� journals in the field is confirmed by the citation data presented here since all three ASA journals are included among these 11.
 

REFERENCES
 

1. back to text  Garfield, E. 1986. Which medical journals have the greatest impact? Ann. Intern. Med. 105:313�320. pdf file available

2. back to textGarfield, E. 1981. Bradford�s law and related statistical patterns. p. 476�483. In E. Garfield (ed.) Essays of an information scientist. Vol. 4. ISI Press, Philadelphia. pdf file available

3. back to textSmall, H., and E. Sweeney. 1985. Clustering the Science Citation Index using co-citations. I. A comparison of methods. Scientometrics 7:391�409.

4. back to textSmall, H., E. Sweeney, and E. Greenlee. 1985. Clustering the Science Citation Index using co-citations. II. Mapping science. Scientometrics 8:321�340.

Editors� note:

1 back to text  Crop Science ranked 2nd and 3rd in terms of citations to the core and from the core, respectively, but its impact was 23rd in the list of core journals.