Weed-crop Competition: A Review

229 Pages·2007·1.38 MB·english

by  Robert L. Zimdahl

Weed-Crop
Competition
A Review
Second Edition
Weed-Crop
Competition
A Review
Second Edition
Robert L. Zimdahl
Robert L. Zimdahlis Professor of Weed Science, Authorization to photocopy items for internal or per-
Colorado State University,and edited the Journal sonal use,or the internal or personal use of specific
Weed Sciencefrom 1994 to 2002. clients,is granted by Blackwell Publishing,provided
that the base fee of $.10 per copy is paid directly to
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Library of Congress Cataloging-in-Publication Data
Blackwell Publishing Ltd
9600 Garsington Road,Oxford OX4 2DQ,UK Zimdahl,Robert L.
Tel.:[phone] Weed-crop competition :a review / Robert L.
Zimdahl—2nd ed.
Blackwell Publishing Asia p. cm.
550 Swanston Street,Carlton,Victoria 3053,Australia Includes bibliographical references (p.).
Tel.:[phone] ISBN 0-8138-0279-2 (alk. paper)
1. Weeds. 2. Plant competition. 3. Weeds—
Bibliography. 4. Plant competition—Bibliography.
I. Title.
SB611.Z55 2004
632'.5—dc22
2003023656
The last digit is the print number:9 8 7 6 5 4 3 2 1
In order to penetrate ever further into their subjects, the host of specialists narrow
their fields and dig down deeper and deeper till they can’t see each other from hole
to hole. But the treasures their toil brings to light they place on the ground above.
A different kind of specialist should be sitting there, the only one still missing.
He would not go down any hole, but would stay on top and piece all the different
facts together.
—Thor Heyerdahl,Aku-Aku:The Secret of Easter Island
Contents
Preface ix
1 Introduction:An Historical Perspective 1
2 Definition of Plant Competition 6
3 Competition in the Community 9
Plant Communities 9
Agricultural Communities 10
Levels of Competition 10
Density 13
Community Composition 14
Theories of Competition 16
4 Influence of Competition on the Plant 19
Density 19
Competitive Ability 19
General Principles 20
Competitive Success 22
5 The Effect of Weed Density 27
Alfalfa 28
Barley 28
Corn/Maize 32
Cotton 39
Oilseed Crops 46
Flax 46
Rapeseed/Canola 46
Safflower 48
Sunflower 48
Peanut/Groundnut 49
Potato 51
Rice 52
Sorghum 56
Soybean 57
Sugarbeet 75
Sugarcane 77
Vegetables 78
Bean 78
Lentil and Chickpea 80
vii
viii Contents
Onion 81
Pea 81
Pepper 82
Tomato 83
Other Vegetable Crops 86
Wheat 88
Other Small Grain Crops 103
Studies of Diverse Crops 104
Weed-Weed Interference 106
6 The Effect of Competition Duration 109
7 The Elements of Competition 131
The Role of Temperature 132
Competitive Interactions for Nutrients 133
Competitive Interactions for Light 136
Competitive Interactions for Water 139
Competition for Other Environmental Factors 141
8 Weed Management Using the Principles of Competition 146
Plant Arrangement in the Community 147
Monoculture Versus Polyculture 149
Tillage 150
Rotation or Crop Sequence 153
Shade 155
The Role of Crop Genotype 156
Fertility 159
The Importance of Weed Biology and Ecology 160
9 Methods Used to Study Weed-Crop Competition 167
10 Models and Modeling 173
Conceptual Models 174
Simulation (Analytical) Models 174
Mechanistic or Empirical Models 176
Time of Emergence 179
Leaf Area Models 179
Multispecies Competition 182
The Extrapolation Domain of Models 183
Decision-Aid Models 183
Spatial Distribution 185
The Effect of Variability on Decisions 186
Thresholds 187
Conclusion 190
11 Conclusion:The Complexity of Competition 197
Appendix 200
Index 211
Preface
The primary impetus for the first edition of this weed science: Weeds compete with crops and
work twenty years ago came from my opinion, reduce crop yield and quality.
formed from limited international experience in the This hypothesis is rarely stated in scientific
1970s, that many weed scientists in developing papers about weeds because it has dominated the
countries did not receive and were not aware of cur- thinking in weed science for so long that it is
rent weed science literature (see Zimdahl 1980). axiomatic. After all,if it were proven to be false and
They had limited or no access to journals common- if it were discovered that crops tolerated weeds,the
ly found in libraries of the developed world. Thus, world would not need weed scientists. There would
they were denied use of printed resources that help be no problems with weed-crop competition. How-
develop an historical perspective. Often,they did not ever,the first edition of this book,published in 1980,
know what was known. An historical perspective showed that weed-crop competition is real and its
combined with the stimulation of current research effects had been studied in many ways, in many
sharpens the focus of research programs and facili- crops, for many years. The hypothesis that weeds
tates their justification to administrators and funding negatively affect crop yield and quality has been
agencies. Lack of access to the literature can narrow tested and verified; it is accepted.
one’s perspective and usually impedes development However, weed science, similar to most disci-
of good weed science programs. plines,continues to test its central hypothesis. Weed
Because no comprehensive review of weed-crop scientists have been productively engaged in what
competition had been published and because Kuhn (1970) calls normal science—“the activity in
approval had been given for the project by the Inter- which most scientists inevitably spend almost all
national Plant Protection Center at Oregon State their time.”It is,in Kuhn’s view,“predicated on the
University, there was additional motivation for the assumption that the scientific community knows
first edition. what the world is like.”It is a “strenuous attempt to
The literature review for the present book began force nature into the conceptual boxes supplied by
in mid-2001 in the library of the International Rice professional education.” Thus, the weed science
Research Institute (IRRI), Los Banos, Laguna, community has continued to test its central hypoth-
Philippines. The review was completed and writing esis about how weeds negatively affect crops. Weed
began in late 2002. When the review began,I was a scientists are moving,albeit slowly,from the normal
Fulbright Scholar in the Department of Agronomy science that repetitively asks what happens,
of the University of the Philippines at Los Banos, although this review establishes that these experi-
and Dr. James Hill, chair of IRRI’s Department of ments are still done, to the more difficult but more
Crop,Soil,and Water Sciences,graciously offered a important and more scientifically demanding ques-
courtesy appointment and access to IRRI facilities. tion of why does what is observed occur.
The Philippines, a place where weeds grow abun- The first edition of this book was a report of what
dantly,was an appropriate location to begin to think had been done by whom. It included articles direct-
again about what may be the central hypothesis of ly related to weed-crop competition published prior
ix
x Preface
to June 1978. This second edition is an attempt to in design and result. I assure the reader that I recog-
summarize the literature about what is known about nized the risk and suffered while writing from repe-
what happens and to explore current understanding tition. The work assembled here is a resource,and I
of why. A goal is to urge a decrease of effort direct- hope one result will be that a lot more work to
ed toward answering the first question and an explain what happens when weeds interfere with
increase of effort on the second. In spite of criticism crop growth will not be done.
of what has been done, I hasten to add that I have Authors resist and editors insist on uniformity and
been continually impressed with the quality of the a limited set of notations and measurement systems.
work and by the people who have done it. I have The current convention of using only metric units
been most impressed by many of the papers and was tempting. However,readers who elected to con-
reviews mentioned here that are superlative work sult a particular paper would need to convert back to
done by capable people whose scientific knowledge the original units. Therefore,the units from original
and skills often seem to extend beyond my analyti- papers were used without conversion to metric. A
cal and review ability. I am humbled by what my short conversion table has been included as appen-
colleagues have done. dix table A.4.
Unless warranted, this second edition will not All weeds are cited by the common or scientific
reconsider but will include some of the manuscripts name (if no common name has been accepted by the
used in the first edition. To this end, I begin this Weed Science Society of America). Equivalent sci-
review at the end of the first edition and go forward. entific and common names, accepted by the Weed
Older material is included for historical reasons and Science Society of America,are included in appen-
to make certain points. The book’s focus is interfer- dix table A.2,which lists them in alphabetical order
ence in the narrow sense of crop-weed competition. by common name,and in appendix table A.3,which
The abundant recent literature on weed biology and lists them in alphabetical order by scientific name.
weed ecology is not included unless such studies The scientific name of each crop is included in
directly address competition. There was no attempt appendix table A.1.
to include any of the literature on allelopathy,which Most papers selected for inclusion specifically
has been summarized by others (Inderjit et al. 1995, discuss weed-crop competition. Others provide
1999; Putnam and Tang 1986; Rice 1974, 1979, background information. Most literature concerning
1983; Thompson 1985). It is my limitation, but in crop-crop interactions has been omitted as has that
most cases,the review includes only literature pub- dealing with environmental conditions that stress
lished in English with emphasis on American and crops (e.g., low water, high temperature) and
European journals of weed science. There are increase their susceptibility to weed competition.
exceptions, but, in general, this review does not The second edition follows the general outline of
include papers published in the proceedings or the first edition. A chapter on modeling and a more
research progress reports of U.S. regional (e.g., detailed chapter on methods have been added.
northeastern, north central, southern, or western)
societies of weed science and by other regional LITERATURE CITED
weed conferences (e.g.,Asian-Pacific Weed Science
Inderjit,K. M. M. Dakshini,and C. L. Foy,ed. 1999.
Society, Canadian Weed Science Society). This is
Principles and practices in plant ecology:
the case because the review emphasizes papers that
Allelochemical interactions. Boca Raton,FL:CRC
have passed peer review and been published in ref-
Press.
ereed journals. Second, many regional publications
Inderjit,K. M. M. Dakshini,and F. A. Einhellig,ed.
were not readily available to me. Finally,papers that
1995. Allelopathy:Organisms,processes,and
emphasized herbicides or other weed management
applications. Amer. Chem. Soc. Symp. Series No.
techniques have not been reviewed. Readers will
268. Washington,DC.
note that much of what has been included seems Kuhn,T. S. 1970. The structure of scientific
repetitious. Roget’s thesaurus helps, but not much, revolutions. 2d ed. Chicago:University of Chicago
when one wants to say that someone or a paper Press.
showed, discovered, revealed, noted, or found. The Putnam,A. R.,and Chung-Shih Tang,ed. 1986. The
ways to say what was discovered are limited,espe- science of allelopathy.New York:John Wiley and
cially when so much of the work included is similar Sons.
Preface xi
Rice,E. L. 1974. Allelopathy. New York:Academic Thompson,A. C.,ed. 1985. The chemistry of
Press. allelopathy:Biochemical interactions among plants.
———. 1979. Allelopathy—An update. Bot. Rev. Amer. Chem. Soc. Symp. Series No. 268.
45:15–109. Washington,DC.
———. 1983. Pest control with nature’s chemicals: Zimdahl,R. L. 1980. Weed-crop competition:A
Allelochemicals and pheromones in gardening and review. Corvallis,OR:Int. Plant Prot. Center,
agriculture.Norman:Oklahoma University Press. Oregon State University.
Weed-Crop Competition: A Review, Second Edition
Robert L. Zimdahl
Copyright © 2004 by Blackwell Publishing Ltd
1
Introduction:
An Historical Perspective
Two of the earliest references on the effects of weed stances left by preceding crops. One of the first stud-
competition appear in ancient writings of the Bible: ies of plant competition was by Sachs (1860), who
“Cursed is the ground for thy sake; in sorrow shalt attempted to relate soil mass to plant yield. Nageli in
thou eat of it all the days of thy life; thorns also and 1865 (cited in Clements et al. 1929) broadened the
thistles shall it bring forth to thee; and thou shalt eat significance of competition in the plant community,
the herb of the field” (Genesis 3:17–18). Another pointing out that it furnished a solution to the prob-
passage,the parable of the sower,notes that,“some lems involved with the presence of lime in soil.
fell among thorns; and the thorns sprang up, and Malthus (1798) was concerned primarily with
choked them”(Matthew 13:7). growth of the human population and the consequent
It is correct to suggest that competition among poverty and misery he saw in Liverpool, England.
plants precedes recorded history and that it was rec- He proposed that the power of population was infi-
ognized long before a defined term was assigned. nitely greater than the earth’s ability to produce
Competition among plants in natural communities is food. The Malthusian apocalypse, when the human
common, but it is not a universal phenomenon population is greater than the ability of the earth to
(Goldberg 1990). However, in agricultural plant produce food,has been avoided because of develop-
communities, weed-crop competition, with a few ments in food production technology. Competition
exceptions (e.g., living mulches, companion crop- for food, if the Malthusian apocalypse comes true,
ping),seems to be a natural,undesirable,ubiquitous, still concerns many. Malthus said, “The cause to
and inevitable phenomenon. which I allude is the constant tendency in all ani-
Competition is a predictable response of grouping mated life to increase beyond the nourishment pre-
living organisms into communities. Clements et al. pared for it.” The Malthusian hypothesis has three
(1929, p. 3) provided an early history of the litera- major points:
ture, which they claimed was “not extensive.” The
1. Population is necessarily limited by the
book by Clements et al. (1929), although perhaps
means of subsistence.
not extensive, provides an accurate historical per-
2. Population infinitely increases when the
spective on the early development of the study of
means of subsistence increase unless it is
plant competition. Competition was recognized and
controlled by powerful checks.
reported by Petrus de Crescentiis in 1305 when he
3. These checks that suppress the superior
directed that trees in a forest community be cut first
power of population and keep population and
where they were too thick. The significance of com-
the means of subsistence in balance are
petition in the plant kingdom was perhaps first per-
resolvable by moral restraint,or population
ceived by Decandolle (1820) who described plant
will be controlled by the four horsemen of
competition and stated that all species of a region
the apocalypse:war,famine,pestilence,and
and all plants of a given place are in a state of war
vice.
with respect to each other. He derived a theory of
antagonism between phanerogams, and a theory of Malthus’s views are claimed by some to have
crop rotation based on the idea that succeeding been inspiration for Darwin’s (1859) principle of
species should be those not inhibited by toxic sub- natural selection. Darwin (1859) derived the concept
1