Table Of ContentSpringer Japan KK
N. Ae, J. Arihara, K. Okada, A. Srinivasan
(Eds.)
Plant Nutrient Acquisition
New Perspectives
With 230 Figures, Including 6 in Color
, Springer
NORIHARU AE, Ph.D.
Laboratory of Soi! Biochemistry
National Institute for Agro-Environmental Sciences
3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan
JOJI ARIHARA, Ph.D.
Legume Physiology Laboratory
National Institute of Crop Science
2-1-18 Kannondai, Tsukuba, Ibaraki 305-8518, Japan
KENSUKE OKADA, Ph.D.
Crop Production and Environment Division
Japan International Research Center for Agricultural Sciences
1-1 Owashi, Tsukuba, Ibaraki 305-8686, Japan
ANCHA SRINIVASAN, Ph.D.
Regional Science Institute
4-13, Kita-24 Nishi-2, Kita-ku, Sapporo 001-0024, Japan
ISBN 978-4-431-66904-3 ISBN 978-4-431-66902-9 (eBook)
DOI 10.1007/978-4-431-66902-9
Library of Congress Cataloging-in-Publication Data
Plant nutrient acquisition: new perspectives I N.Ae, .... [et al.], (eds.)
p.cm.
Paper presented at the International Workshop held in Tsukuba, Japan, March 24-27, 1998.
Includes bibliographical references (p. ).
ISBN 978+431-66904-3
1. Plants--Nutrition--Congresses. 2. Plant-soil relationships--Congresses. 3. Roots
(Botany)--Congresses. 4. Plant nutrients--Congresses. 1. Ae, N. (Noriharu), 1946-
QK867 .P53 2001
575.7'6--dc21
Printed on acid-free paper 2001020401
© Springer Japan 2001
Originally published by Springer Verlag Tokyo Berlin Heidelberg New York in 2001
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SPIN: 10691853
Foreword
KATSUYUKI MINAMI
Director General, National Institute for Agro-Environmental Sciences (NIAES)
Plant Nutrient Acquisition: New Perspectives is a compilation of research papers
presented at the International Workshop held in Tsukuba, Japan, March 24-27,
1998. The Workshop was organized by the National Institute of Agro-Environ
mental Sciences (NIAES) and was sponsored by the Secretariat of the Research
Council of the Ministry of Agriculture, Forestry and Fisheries, Japan.
The objectives of the Workshop were to discuss newly emerging concepts of
the mechanisms that plants use to acquire soil nutrients, and to relate those con
cepts in the context of applied agriculture. Some 40 papers and posters highlight
ing recent advances in this exciting field were presented. I greatly appreciate the
efforts of the authors in critically evaluating the past work and presenting new
experimental findings and concepts of both theoretical and applied significance.
The scope of the Workshop was defined by the Organizing Committee-the
members of which are the editors of this book-by holding regular discussions
for one year prior to the Workshop. The Committee also received excellent pro
fessional support from several staff members and researchers of NIAES in orga
nizing the Workshop. I express my sincere thanks to all of them.
I am confident that this book will serve as a valuable reference for researchers,
students, and extension staff in their efforts to develop more effective approaches
to sustainable nutrient management.
May 2001
v
Welcoming Address
MICHINORI NISHIO
Professor, University of Tsukuba
Former Director General, National Institute for Agro-Environmental Sciences (NIAES)
On behalf of the Organizing Committee and the National Institute of Agro-Envi
ronmental Sciences, I extend a warm welcome to all of you. The concept of sus
tainable agriculture has become the most important concern in the global farm
ing sector since the Earth Summit in Rio de Janeiro in 1992. The concept itself is
beautiful, and no one denies that. However, there are many interpretations of this
concept. It is quite natural to have such diverse interpretations, as types of agri
culture vary widely across countries, regions, and areas, depending on different
natural and social conditions.
Broadly speaking, there are two types of agriculture: extensive and intensive.
Different factors are threatening sustainability of both types. For example, the
deficiency of nutrients is threatening extensive agriculture while the surplus of
nutrients is damaging intensive agriculture. One of the most important concerns
for sustainable agriculture, therefore, is the management of plant nutrients. In
intensive agriculture, overuse of chemical fertilizers is a matter of concern, while
in extensive agriculture, acquisition of nutrients from alternatives to chemical
fertilizers is of main interest. There are many ways to approach sustainable nutri
ent management, including the utilization of slow-release fertilizers, improvement
of fertilization methods, utilization of renewable resources, recycling of farm
wastes, and so on. But I am convinced that the essential approach to sustainable
nutrient management is the utilization of biological functions of plants and soil
organisms. While studies on the role of microorganisms in relation to nutrient
supply are relatively many, there are few studies on plant nutrient acquisition. I
believe that effective utilization 'of nutrient acquisition mechanisms by plants
themselves and by plant-soil organism combinations is a fundamental and reli
able approach to sustainable nutrient management in both intensive and exten
sive agriculture.
With these considerations, the Organizing Committee planned this Workshop.
The Committee made special efforts to identify and send invitations to distin
guished international experts in various fields. I am happy to learn that almost
all invited researchers kindly agreed to participate and share their views with us.
I am especially glad to see Dr. Swindale and Dr. Johansen, who extended valuable
help to the Committee members in their research at International Crops Research
Institute for the Semi-Arid Tropics (ICRISAT).
VI
Welcoming Address VII
Let me once again welcome all of you to Tsukuba and wish you success in your
research endeavors. I am confident that discussions held here will lead to new
collaborations that will guide plant nutrition research in the years ahead.
March 1998
Preface
LESLIE D. SWINDALE
Director General (Emeritus), International Crops Research Institute
for the Semi-Arid Tropics (ICRISAT)
Plants, like people, need food.
The scientific study of plant nutrients commenced in the mid-nineteenth century
with the work of Justus von Liebig and his application of scientific principles to
"the means of nutrition of vegetables and with the influence of soils and action of
manures upon them:' Liebig proposed the Law of the Minimum, that is, that plant
growth was dependent upon the least available nutrient. Soon after the turn of
the century it was accepted that the primary means of nutrient uptake was by ion
exchange at root surfaces with H+ ions being released from the roots in cation
uptake and OH- and HC0 being released in the uptake of anions. By the early
3-
1920s it was recognized that nutrient supply to any plant was dependent upon
both the amount of nutrient available in the surrounding soil and the rate at which
the nutrient was supplied to the plant, the so-called capacity and intensity factors.
After it was realized that nutrients would first need to pass into the soil solution
that existed between the soil and the plant roots-although some adhered to the
idea of nutrient supply through direct contact between the solid phases of soil
and plant- a physico-chemical model of nutrient uptake was developed and held
sway for several decades. In this model there were basically three rate-determin
ing steps: the rate at which a nutrient was removed from the soil particle into the
soil solution, the rate at which the nutrient diffused through the solution, and the
rate at which it was subsequently taken up by the plant.
The model, to this stage, was essentially a physical one. Jacobsen and Overstreet
in the 1960s were among the first to introduce a biological dimension by propos
ing that organic chelating compounds occurred in the soil solution and affected
both the removal of ions from the soil and the activities of ions in solution. The
metabolic products of the microbial breakdown of carbohydrates in soils include
citrate, malate, and malonate, all of which have chelating abilities. In more recent
years the possible role of enzymes in nutrient release and particularly in nutrient
uptake has received attention.
Chelating compounds would have particular importance on the availability of
phosphate (P), which is one of the three most important nutrients that plants
derive from soils. It is often one of the least available because it can be fixed in
unavailable forms and because it is not very mobile in soil solutions. Plants for
age for P. Several authors have shown how P uptake is related to the total mass
VIII
Preface IX
and volume of roots. Nitrogen can influence P uptake not only by increasing the
root mass but also by altering the nature of root systems.
The Workshop on New Concepts of Plant Nutrient Acquisition, held at Tsukuba,
Japan, March 24-27, 1998, the proceedings of which are reported in this publica
tion, brought together people from allover the world to exchange views on old
and new perspectives of plant nutrient uptake and to show how the newer per
spectives might be applied to practical agriculture. It was to a large extent an
outgrowth of a 15-year-Iong project between International Crops Research Insti
tute for the Semi-Arid Tropics (ICRISAT) and the Japan International Research
Center for Agricultural Sciences (JIRCAS), with core support from the Consulta
tive Group on International Agricultural Research (CGIAR) and special project
support from the Government of Japan.
The project, entitled "Development of Sustainable Cultivation of Upland Crops
in the Semi-Arid Tropics:' was conducted in three phases (I: 1984-1989,11: 1989-
1994, III: 1995-1999). During that time Japanese scientists worked at ICRISAT
with ICRISAT scientists and fellows. The project addressed the issues of food se
curity and poverty alleviation by looking for ways to increase the availability of
nutrients without additions of fertilizers in food crops commonly used by poor
people in the semi-arid tropics. The project first tried to elucidate the mecha
nisms by which some of these crops were more efficient than others in extracting
nutrients from soils, then studied the role of roots and root development, and, in
the final phase, moved on to learning how plant breeding could be combined with
management options to improve nutrient availability in soils with low nutrient
supplying powers.
We have known for a long time that pigeonpea seemed to be able to extract P
from soils in ways that other crops could not. Project scientists obtained evidence
that suggested that root exudates of pigeonpea might be the cause, or at least a
cause, of the plant's ability to extract P from soil. Piscidic acid was identified as
one of the constituents of the exudates. Mechanisms involving root exudates may
make limited contributions to the P nutrition of most plants in most soils, but
they seemed to be important in the case of pigeonpea growing in soils with low
nutrient-supplying power. This finding was the first report indicating that crop
plants are also able to modify rhizosphere conditions, thereby solubilizing P from
Fe compounds, which are regarded as the most insoluble form of P.
Several papers at the Workshop in Tsukuba further explored the role of plant
exudates in P uptake. Otani and Ae found that pigeonpea, groundnut, and rice
had greater abilities to release P from Fe- and AI-fixed forms in Andosols than
did sorghum if root volume was constrained. Pigeonpea exudates were shown to
be able to dissolve FeP0 and AIP0 in artificial conditions. In addition to piscidic
4 4
acid, malonates and citrates were also found as the components of the exudates. P
uptake by maize and soybean from soils with low available P was enhanced when
artificial pigeonpea exudates were added to the rhizosphere soil. Their effect, in
fact, was to create conditions through which P can be solubilized from the soil so
that absorption by the plant becomes possible.
Papers presented at this workshop highlight various new aspects of plant nu
trient acquisition. One set of papers discusses recent models regarding nutrient
X Preface
uptake that place greater emphasis on the active role of plants in that process.
This is followed by several papers describing management options designed to
reduce the reliance on chemical fertilizer inputs. The important role of soil mi
croorganisms for nutrient acquisition is stressed and evidence presented that
shows that organic fertilizers can be used directly by plants as a result of their
ability to take up organic nitrogen forms. Finally, the potential for improving the
nutrient acquisition ability of crops by plant breeding methods is explored. Re
sults presented indicate that breeding effective crops is possible even for tropical
soils, which have long been considered to be problem soils due to low P-fertility. It
was also shown that another important problem of tropical soils-soil acidity
can be overcome by exploring the genetic diversity present in crop plants. Ge
netic improvements in combination with adjustments in cropping systems will
have a significant impact not only in developing countries characterized by low
fertilizer use but also in developed countries, where they will contribute to mak
ing agricultural systems more environmentally sound.
The organizers of the workshop in an epilogue made a plea for reducing de
pendence upon mineral fertilizers to increase food crop production in and for
the developing world through greater use of natural soil components and pro
cesses. I believe that the publication of these proceedings will stimulate research
into these more sustainable forms of plant nutrient acquisition.
