Management of Biological Nitrogen Fixation for the Development of More Productive and Sustainable Agricultural Systems: Extended versions of papers presented at the Symposium on Biological Nitrogen Fixation for Sustainable Agriculture at the 15th Congress

289 Pages·1995·24.47 MB·English

by  M. B. Peoples

MANAGEMENT OF BIOLOGICAL NITROGEN FIXATION
Developments in Plant and Soil Sciences
VOLUME 65
The titles published in this series are listed at the end of this volume.
Management of Biological Nitrogen Fixation
for the Development of More Productive and Sustainable
Agricultural Systems
Extended versions of papers presented at the Symposium on Biological Nitrogen Fixation
for Sustainable Agriculture at the 15th Congress of Soil Science, Acapu1co, Mexico, 1994
Edited by
J.K. LADHA and M.B. PEOPLES
Reprinted from Plant and SoU, Volume 174, Nos. 1-2 (1995)
SPRINGER SCIENCE+BUSINESS MEDIA, B.V.
A C.I.P. Catalogue record for this book is available from
the Library of Congress.
ISBN 978-0-7923-3414-9 ISBN 978-94-011-0055-7 (eBook)
DOI 10.1007/978-94-011-0055-7
Printed on acid-free papers
AlI Rights Reserved
© 1995 Springer Science+Business Media Dordrecht
Origina11y published by Kluwer Academic Publishers in 1995
No part of the material protected by this copyright notice
may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying,
recording, or by any information storage and retrieval
system, without written permission from the copyright
owner.
Contents
Preface 1
1. Biological nitrogen fixation: An efficient source of nitrogen for sustainable agricultural
production?
M.B. Peoples, D.F. Herridge and J.K. Ladha 3
2. Sustainable agriculture in the semi-arid tropics through biological nitrogen fixation in grain
legumes
S.P. Wani, O.P. Rupela and K.K. Lee 29
3. Enhancing crop legume N2 fixation through selection and breeding
D.F. Herridge and S.K.A. Danso 51
4. Enhancing legume N2 fixation through plant and soil management
M.B. Peoples, J.K. Ladha and D.F. Herridge 83
5. Role of legumes in providing N for sustainable tropical pasture systems
R.J. Thomas 103
6. Management of biological N2 fixation in alley cropping systems: Estimation and contribu
tion to N balance
J. Sanginga, B. Vanlauwe and S.K.A. Danso 119
7. Manipulation of rhizobia microflora for improving legume productivity and soil fertility: A
critical assessment
J. Brockwell, P.J. Bottomley and J.E. Thies 143
8. Green manure technology: Potential, usage, and limitations. A case study for lowland rice
M. Becker, J.K. Ladha and M. Ali 181
9. Biological nitrogen fixation associated with sugar cane and rice: Contributions and prospects
for improvement
R.M. Boddey, O.C. de Oliveira, S. Urquiaga, V.M. Reis, F.L. de Olivares, V.L.D. Baldani
and J. Dobereiner 195
10. Biological N2 fixation by heterotrophic and phototrophic bacteria in association with straw
M.M. Roper and J.K. Ladha 211
11. Potential and pitfalls of trying to extend symbiotic interactions of nitrogen-fixing organisms
to presently non-nodulated plants, such as rice
F.J. de Bruijn, Y. Jing and F.B. Dazzo 225
Contents
12. New techniques for studying competition by Rhizobia and for assessing nitrogen fixation in
the field
KJ. Wilson, M.B. Peoples and R.A. Jefferson 241
13. Future benefits from biological nitrogen fixation: An ecological approach to agriculture
K.E. Giller and G. Cadisch 255
14. Research evaluation and impact analysis of biological nitrogen fixation
M.e.S. Bantilan and C. Johansen 279
Author index 287
Plallt alld Soil 174: 1. 1995.
© 1995 Kluwer Academic Publishers.
Preface
Management of biological nitrogen fixation for the are examples of sound BNF technology but farmers'
development of more productive and sustainable adoption of them has been disappointing to scientists,
agricultural systems extension workers, and policymakers. Inoculating Rhi
zobium into legumes mostly results in increased bio
Nitrogen is the most important nutrient input required logical yield, except for soybean where economic yield
for crop production. Soil and biological nitrogen fixa is often increased. Although higher biological yield
tion (BNF) and chemical sources supply most of that improves long-term soil fertility, it does not provide
N. Soil organic N in natural or man-made ecosystems immediate cash benefits to farmers. The result is non
is continually lost through plant removal and loss pro adoption. Likewise, green manuring has tremendous
ces~es such as leaching, de.llitiification, and ammonia potential as a substitute for chemical fertilizers but
volatilization. Biological nitrogen fixation - the micro is often found to be uneconomical because govern
bial conversion of atmospheric N to a plant-usable form ments commonly subsidize fertilizer. Many resource
- helps replenish the soil N pool. 'management technologies face a siinilar dilemma. Our
The subsistence agriculture of the pre-chemical era research needs to take a holistic rather than a reduction
efficiently sustained the N status of soils by main ist approach. Admittedly, a holistic approach is more
taining a balance between N loss and N gain from expensive.
BNF. This was possible with less intensive cropping, A single technology - improved crop genotypes -
adoption of rational ~rop rotations and intercropping has contributed the most to productivity increase in
schemes, and use of legumes as green manure. The modern agriculture. The adoption of a new genotype
agriculture of the modern chemical era concentrates by farmers is usually very high because no addition
on maximum output but overlooks input efficiency; it al cost is involved and existing cropping systems and
has not been sustainable. Intensive monocropping with soil and water management practices are not affect
no or inadequate crop rotations or green manuring and ed. Although the goal to make cereals fix their own
excessive use of chemical N fertilizers results in an nitrogen is of long-tenp. nature and the funding for
imbalance between N gains and N losses. The losses research is greatly constrained by concerns of failure,
are often larger than the gains, and soil N status goes if achieved, would have a significant impact on agri
to a lower level. Agricultural systems, however, dif culture world-wide.
fer in levels of N sustainability. An irrigated double This volume is devoted to discussions on the role
rice cropping system, for example, can be sustained at of BNF in agricultural sustainability. Papers present
a higher level than can a rainfed single rice cropping ed on BNF in crop forage and tree legumes are aug
system. The challenge is to sustain soil N fertility in mented with discussions on integrated farming sys
cropping systems operating at high productivity lev tems involving BNF, soil and N management, and
els. This requires judicious integration of BNF com recycling of legume residues. BNF by non-legumes
ponents, which keeps a good balance between N losses are discussed and attempts to transform cereals into
and gains. nodulating plants are critically reviewed. Advances
Sustainability of N cannot be considered in iso on the development of novel methodologies to under
lation; it must be considered holistically within the stand symbiotic interactions and to assess N2 fixation
framework of system sustainability. A BNF technolo in the field are described and means of enhancing
gy must be economically viable, ecologically sound, BNF through plant and soil management, or breed
and socially acceptable to be successful. Although all ing and selection are presented. Problems encountered
of these aspects are important, economics often deter in exploiting BNF under farmers' field conditions and
mine the value of a technology. There are frequent promising approaches to improve BNF exploitation are
conflicts between economy and ecology: a technology examined.
that is more sound ecologically may not be viable eco J KLadha
nomically. Rhizobium inoculation and green manuring Chairman of the Symposium
Plant and Soil 174: 3-28. 1995.
© 1995 Kluwer Academic Publishers.
Biological nitrogen fixation: An efficient source of nitrogen for sustainable
agricultural production?
M.B. Peoples 1 ,D.E Herridge2 and 1.K. Ladha3
1 CSIRO Division of Plant Industry, GPO Box 1600 Canberra, ACT 2601, Australia, 2 NSW Agriculture. RMB 944
Tamworth, NSW 2340, Australia and 3lntemational Rice Research Institute. PO Box 933, 1099 Manila,
Philippines
Key words: Azolla, Casuarina, legume, nitrogen fertilizer, rhizobia, symbiotic N2 fixation
Table of contents
Abstract
Introduction
Fertilizer-N inputs into agriculture
Measured inputs of fixed N
Food legumes
Forages legumes, green manures and N-fixing trees
2
BNF in farmers' fields
Contributions of BNF to the soil N pool and associated rotational effects
Utilization of fertilizer or organic sources of N
Cropping systems
Forage systems
Agroforestry systems
Can the use of BNF as a N source improve farm profitability?
Conclusions
Acknowledgements
References
Abstract
A fundamental shift has taken place in agricultural research and world food production. In the past, the principal
driving force was to increase the yield potential of food crops and to maximize productivity. Today, the drive for
productivity is increasingly combined with a desire for sustainability. For farming systems to remain productive,
and to be sustainable in the long-term, it will be necessary to replenish the reserves of nutrients which are removed
or lost from the soil. In the case of nitrogen (N), inputs into agricultural systems may be in the form ofN-fertilizer,
or be derived from atmospheric N2 via biological N2 fixation (BNF).
Although BNF has long been a component of many farming systems throughout the world, its importance as
a primary source of N for agriculture has diminished in recent decades as increasing amounts of fertilizer-N are
used for the production of food and cash crops. However, international emphasis on environmentally sustainable
development with the use of renewable resources is likely to focus attention on the potential role of BNF in
supplying N for agriculture. This paper documents inputs of N via symbiotic N2 fixation measured in experimental
plots and in farmers' fields in tropical and temperate regions. It considers contributions of fixed N frem legumes
(crop, pasture, green manures and trees), Casuarina, and Azolla, and compares the relative utilization ofN derived
from these sources with fertilizer N.
4
Introduction
Table 1. Global allocation of arable land between different com
modities
Globally, cereal cropping dominates cultivated land
use (around 50% of total area, Table 1). The remain Commodities' Proportion of land area
ing arable land is used for production of oilseed, fibre, (%)
or food and cash crops. In addition, vast areas are
Cereals
maintained under temporary or permanent pasture for Wheat 16
forage production (2-3 fold greater than the total area Rice 10
under cultivation and permanent crop; Table 1, Fig. Maize 9
1). All cultivated crops, except for legumes (pulses All other cereals 13
and legume oil seeds) require the soil to provide rel
atively large amounts of nitrogen (N). It is necessary Total 48
for the three most important cereals, wheat (Triticum
aestivum), rice (Oryza sativa) and maize (Zea mays), Legumes
to take up 20 to 40 kg soil N ha -lover a period of 3 Legume pulses 5
to 5 months to satisfy the N requirements of the seed Legume oilseeds 6
and supporting vegetative structure for each tonne of
grain produced (e.g. Fig. 2; Myers, 1988). Produc Total II
tive pastures on the other hand may assimilate> 100
Other crops
kg N ha-I each annum, of which 50 to 90% will be
Other oilseeds 6
consumed by livestock in intensively grazed systems
Beverages / Tobacco 7
(Ledgardy, 1991; Thomas, 1995). Even though 75 to
Roots and tubers 4
95% of the N ingested is returned as excreta, large
Sugars 2
amounts of N can be leached or lost as gaseous emis
Vegetables and fruits 2
sions (Peoples et aI., 1994e; Steele and Vallis, 1988),
Fibres / Rubber / Oil palm
so that the annual demand for N can be continuing and
substantial. Total 22
The problem facing farmers everywhere is that the
capacity of their soils to supply N declines rapidly once Temporary pastures / Fodder crops 14
agricultural activities commence and N derived from Other 6
the breakdown of soil organic matter must be supple
mented from other ~ources (Herridge et aI., 1994a). • Distribution of 1442 million ha estimated to be arable land and
under permanent crop in 1991-1992 (FAO, 1992b, 1993),
During the 1990s, around 1 billion additional people
will be added to the 1990 population of 5.3 billion.
Over 90% of the increase will occur in the developing
countries of Asia, Africa and Latin America, where, prairies (on average by 24 kg N ha-I yr-I, Doyle and
already, nearly 1 billion people endure some degree of Cowell, 1993) and Kenya (by 112 kg N ha-I yr-I,
malnutrition. For productivity to be simply sustained Sanchez, 1994). Clearly where agricultural activities
at current levels, let alone improved in the future, the are currently "mining", soil reserves, external nutri
N removed in agricultural produce or lost from the sys ent inputs in the form of fertilizer and BNF must be
tem, must be replaced by N derived either from nitroge increased if farmers are to have any prospect of meet
nous fertilizers, or biological N2 fixation (BNF). It is ing the food and fibre requirements of a growing world
difficult to judge whether farmers are mindful of this population.
concept and manage their N resource accordingly. Evi Fertilizer N is a convenient and (currently) cheap
dence suggests that inputs of fertilizer N might well source ofN for crop growth which provides opportuni
exceed N removal in intensively managed arable soils ties for strategic and rapid applications of plant nutri
of the USA and Europe (Sanchez, 1994); however, ents. However, the use of fertilizer-N in different agri
amounts of N removed from farms in grain or hay and cultural systems is ultimately regulated by economic
lost through runoff, erosion, leaching and denitrifica considerations (e.g. per capita income, credit facilities,
tion have been calculated to exceed inputs by fertilizer the current commodity value and expected return for
and BNF in the agricultural systems of the Canadian investment at a farmer level, and availability of for-
5
food security can be more important than productivity,
and consider the role that BNF can play in reducing
the level of production risk and managing agriculture's
resource base (Giller and Cadisch, 1995).
If BNF is to represent a reliable renewable resource
for sustainable agriculture, its rate of use will be lim
ited by its rate of regeneration and use by non-N2-
1000 fixing crops and grasses. Therefore, it is necessary to
know:
(a) The amounts of N fixed by different N2-fixing sys
ForesV Permanenl Cullivaled Annual Other tems in a range of environments,
Woodland grassland grassland! and arable
fodder pereMial land (b) The contribution of BNF to the soil N pool,
Clops crops
(c) The recovery and losses of N derived from BNF
Land use
sources, and
Fig. 1. Global patterns of land use indicating the relative areas
(d) Options that are available to enhance BNF inputs.
under cropping and temporary or permanent pasture (used for forage
production for 5 years or more), or containing forests and woodlands Examples of N2 fixation inputs observed by
(data from FAO, 1993). researchers at experimental sites and in farmers' fields
will
be described, and the ultimate fate of that N will be
discussed and compared with N from fertilizer in the
eign exchange at a national level), and the presence of following sections. Various approaches that are avail
effective infrastructures for fertilizer production and able to increase BNF are described in following papers
distribution. This taken in conjunction with the poor in this volume.
efficiency of utilizati9n of fertilizer N by crops (sel Most attention will be directed towards N2 fixation
dom exceeding 50%) and increasing awareness of the inputs by legumes because of their proven ability to fix
environmental costs of N lost from fertilizers (Bohlool N2 and contribute to integrated agricultural production
et al., 1992; Craswell and Godwin, 1984; Peoples et systems in both tropical and temperate environments.
aI., 1994e), suggests that there is likely to be a limit Crop legumes alone occupy 11 % of land under culti
to the amounts of fertilizer N that farmers' might be vation or permanent crop (Table 1). However, legumes
willing to apply to improve agricultural production in are also present in some of the 3541 million ha esti
the long-term. The contribution of BNF to the N-cycie mated to be temporary and permanent pastures (Fig.
on the other hand can be controlled by manipulating 1), and may provide valuable inputs of N in natural
various physical, environmental, nutritional or biolog plant communities, forest ecosystems, tree plantations,
ical factors (Hansen, 1994) and may therefore be more and intensive cropping systems (Becker et aI., 1995;
open to management than fertilizer N. Giller and Cadisch, 1995; Hansen, 1994). Discussion
There is growing international concern about issues concerning BNF by non-legumes will be restricted to
of global warming, environmental degradation and loss symbiotic systems involving either:
of natural resources. This concern is summarized in the (a) Anabaena and the aquatic fern Azolla, or
sentiments expressed by Suzuki (1990) : "We no longer (b) Actinorhizal associations: There are far fewer
inherit the Earth from our parents, we borrow it from plant species nodulated by N2 -fixing actinomycetes
our children". With the current emphasis on the use of (Frankia spp.) than Rhizobium-legume associa
renewable resources for environmentally sustainable tions, but their numeric inferiority is offset by
development, it is timely to assess the potential for their capacity to occupy ecological niches where
BNF to complement or replace fertilizer inputs, and to legumes do not thrive. In this particular discussion
consider its contribution to the N fertility of agricultural we specifically consider N2-fixation by the acti
land. Yet we need to achieve more than simply ensuring norhizal association with the tree Casuarina.
that inputs balance outputs. Among other things, we Inputs of N by free-living diazotrophs in soil and
should evaluate the capacity of BNF-based farming plant residues, and non-symbiotic N2-fixing associa
systems to maintain or enhance agricultural production tions with cereals and C4 grasses will not be discussed
in the long term in a way that is economically viable here; however, readers are referred to several recent
and socially acceptable in the short-term. We should publications (e.g. Chalk, 1991; Peoples and Craswell,
also be aware that in some socio-economic frameworks 1992; Roger and Ladha, 1992) and papers presented