AUTHORS
Dan Bennack
Instituto de Ecología, Xalapa, Mexico
George Brown
Embrapa-Soja, Londrina – PR, Brazil
Sally Bunning
FAO Land and
Water Development Division
Mariangela Hungria da Cunha
Embrapa-Soja, Londrina – PR, Brazil
Land and Water Development Division
Land and Plant Nutrition Management Service
Sally Bunning
Particular acknowledgements are gratefully expressed to all the original authors as indicated in each case study.
The third session of the Conference of the Parties (COP) to the Convention on Biological Diversity (CBD), in its development of the programme of work on Agricultural Biodiversity, identified the study of soil micro-organisms as a gap requiring attention (COP decision III/11). Subsequent compilation of case studies and recognition by the Subsidiary Body for Scientific, Technical and Technological Advise (SBSTTA) of the importance of soil biodiversity in the functioning of agricultural ecosystems led to the following decision:
“to establish an International Initiative for the Conservation and Sustainable Use of Soil Biodiversity as a cross-cutting initiative within the programme of work on agricultural biodiversity, taking into account case studies which may cover the full range of ecosystem services provided by soil biodiversity and associated socio-economic factors and, inviting FAO, and other relevant organizations, to facilitate and co-ordinate this initiative” (COP decision VI/5, paragraph 13, Nairobi April 2002).
In particular, FAO recognizes the importance of soil health and improved soil biological management for promoting sustainable agricultural systems and for the restoration of degraded lands. Soil organic matter management and enhanced biological nitrogen fixation (BNF) are already well-known practices in the agricultural and environmental sectors. However, the capacity to enhance soil biological functions through a better understanding of soil biodiversity processes and mechanisms and improved land use systems and practices have been seriously neglected.
Today’s knowledge in this area is, however, fragmented and remains largely in the research domain with limited practical application by farmers. Various reasons include difficulty of observation and limited local understanding of below-ground interactions and processes, specialized research focus and lack of holistic or integrated solutions for specific farming systems, and lack of or inadequate institutional capacity or support services for a concerted resource management approach.
FAO is taking an active role in following up on the above decisions through networking with partners and institutions, collecting and initiating case studies and identifying priorities requiring attention. An important step in this process was the “international technical workshop on biological management of soil ecosystems for sustainable agriculture” organized jointly by EMBRAPA-Soya and FAO in Londrina, Brazil, in June 2002. The review and analysis of case studies from different countries and agro-ecological zones is found to be a useful means of sharing experiences and encouraging collaborative actions. Capacity building is also required, in particular, in the areas of assessment and monitoring and adaptive management for specific agro-ecological and socio-economic contexts, with a view of achieving food security and environmental benefits.
It is well known that farmers’ management practices and land use decisions influence ecological processes and soil-water-plant interactions. However, farmers’ decisions are often made to achieve short-term goals rather than long-term management of soil productivity and health. Unsustainable land use practices and agricultural intensification are significant causes of soil biodiversity loss and related impacts on ecosystem function and resilience. A better understanding of the linkages among soil life and ecosystem function and the impact of human intervention will allow us, not only to reduce the negative impacts, but also to more effectively capture the benefits of soil biological activity for sustainable and productive agriculture.
Given escalating population growth, land degradation and increasing demands for food, achieving sustainable agriculture and viable agricultural systems is critical to food security and poverty alleviation. Soil health and soil quality are fundamental to the sustained productivity and viability of agricultural systems world-wide. Improvement in agricultural sustainability and productivity requires, alongside effective water and crop management, the optimal use and management of soil fertility and soil physical properties, which rely on soil biological processes and soil biodiversity.
The soil is a very complex and multi-faceted environment providing the habitat for a diverse array of soil organisms. The activities of this wide range of soil biota contribute to many critical ecosystem services, including: soil formation; organic matter decomposition, and thereby nutrient availability and carbon sequestration (and conversely greenhouse gas emissions); nitrogen fixation and plant nutrient uptake; suppression or induction of plant diseases and pests; and bio-remediation of degraded and contaminated soils (through detoxification of contaminants and restoration of soil physical, chemical and biological properties and processes). The effects of soil organisms also influence water infiltration and run-off and moisture retention, through effects on soil structure and composition and indirectly on plant growth and soil cover. These services are not only critical to the functioning of natural ecosystems but constitute an important resource for sustainable agricultural production.
The CBD Secretariat has made a call for case studies as a follow-up to decisions on agricultural biodiversity and FAO is assisting in compiling and assessing experiences and lessons learnt. In this process the following six case studies on soil biodiversity/ecosystem management have been selected and reviewed on the basis of their potential to catalyse further work on enhancing the beneficial functions of soil biodiversity for sustainable and productive agriculture and application of the ecosystem approach as adopted by the Convention on Biological Diversity .
The road toward sustainability is not an easy one to follow as short-term economic goals are often perceived to be more desirable by decision makers than the longer-term process of developing socially and technologically acceptable solutions that are also economically viable. In particular, technical assessments, participatory processes of testing and adaptation of improved management practices by farmers/land managers and successful wider application of soil biodiversity management for sustainable and productive agriculture will require adherence to the ecosystem approach.
Application of the guiding principles of the ecosystem approach (as demonstrated through the following case studies) should provide a better understanding of the biological, physical, and human interactions associated with sustainable agro-ecosystems and the ways and means to better manage those interactions with a view to effectively contributing to food security and the well-being of rural populations. Extensive documentation and analysis of such case studies on soil biodiversity management for sustainable and viable production systems (including cropping, pastoral, forestry and mixed systems) will be part of that process. Such case studies should demonstrate the importance of integrated approaches that address and manage interactions between soil and other components of the agro-ecosystem (soil–plant-water–pest-predator interactions in the rhizosphere; soil-plant-livestock-atmospheric interactions through organic matter and nutrient management; and so forth).
The sharing of information, research and development experiences is expected to lead to raised awareness and understanding and wider application of improved soil biological and agro-ecological management approaches that will help ensure environmentally-friendly, productive and sustainable agricultural systems. This will also require policy and institutional support to provide an enabling environment for the adoption of such agro-ecological approaches.
It is hoped that this small selection of cases will encourage a greater compilation and dissemination of similar examples, in accordance with the call for case studies on soil biodiversity by the Conference of the Parties to the CBD and with FAOs mandate for assisting member countries in improving food security and sustainable agriculture.
THE CASE STUDIES PRESENTED HEREIN INCLUDE |
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Agricultural studies of soil systems have historically been directed toward the biophysical and chemical aspects of crop production. The ecological dimensions of soil’s systems have been considered less important. Currently, there is a need to develop greater knowledge of soil ecosystems, and their biological diversity and ecological functions, in order to build a broad basis for sustainable agricultural development. To this end, an ecosystems management approach (see below) is being advocated in many quarters to help carry forward the sustainable agriculture agenda.
This paper represents a selected review of case studies on the management of soil biological diversity for agricultural purposes. Of particular interest is the relevance of each study to the 12 guiding principles of the Convention on Biological Diversity (CBD) Ecosystem Approach1, and the four thematic areas of the CBD/Food and Agriculture Organization (FAO), Programme of Work on Agricultural Biological Diversity2.
The overall scheme for the case study presentations is an outline of the problem to be solved, objectives for the study and actors and actions involved. Results of each study are then discussed and analyzed in the context of the CBD ecosystem approach and the joint CBD/FAO Programme of Work on Agricultural Biological Diversity. Finally, the major outcomes and lessons learnt from each study are summarized.
A Case Study fromNorth America - Tlaxcala, Mexico3
Problem statement
To motivate and empower peasant farming communities in the Central Highlands of Mexico to address the deterioration of soil quality, quantity and biological diversity using sustainable agricultural practices that restore ecosystem functions and meet livelihood needs.
The Central Highlands of Mexico have been under cultivation for thousands of years. Nevertheless, centuries of deforestation occurring since the fall of the Aztec empire at the hands of the Spaniards, plus recent intensive farming practices to feed the burgeoning population of Mexico City, have left soils in these agriculturally critical regions severely eroded and degraded. Deep gullies scour portions of the landscape, affecting water catchment and recharge capacity and reducing the productive potential of natural and agricultural systems. Severely eroded areas (known as tepetates) are characterized by hard, exposed subsoils, virtually no topsoil, and very little below ground life. The deterioration in soil quality, quantity and biodiversity has greatly challenged the capacity of Mexican peasant farmers (campesinos) to maintain even a subsistence living from the land.
Additional constraints to achieving sustainable agriculture, soil biological diversity and ecosystem functioning have been:
Objectives
In the western portion of the state of Tlaxcala, Mexico, also part of the Central Highlands, peasant farmers forming the Vicente Guerrero Group have experimented for more than 20 years with integrated agro-ecological approaches to crop and soil management. Their purpose has been to generate, share, and promote such approaches in order to improve the local quality of life, while respecting and caring for the fragile lands upon which they live.
Actors and activities
The Vicente Guerrero Group (VGG; now a legally registered non-governmental organization in Mexico) is comprised of men and women from Españita, Tlaxcala, who have been acting as agricultural trainers since 1978. Their farmer-to-farmer approaches and rural participatory processes have led to notable successes in the adoption of integrated crop, water and land management practices.
Application of the ecosystem approach to soil biodiversity management
VGG advocates and teaches adaptive management in the maintenance of crop and soil resources, including soil biodiversity. This learn-by-doing approach is consistent with Principle 9 of the ecosystem approach, as adopted by the Convention on Biological Diversity (CBD) though decision V/6 of the Conference of the Parties (COP). These methods are also consistent with Principle 5, which advocates the conservation of ecosystem structures and functions. Adaptive management and conservation methods characterize various Vicente Guerrero programmes, such as:
The production of basic grains using techniques that enhance soil biodiversity functions, including the use of:
Land management that favours plant and animal diversity and its association with soil biological activity. This includes:
Participatory methods and various tools, including:
The philosophical mainstay of the Vicente Guerrero Group is consistent with Principle 1 of the ecosystem approach, that resource management is a matter of societal choice and that benefits should be shared in fair and equitable ways.
To this end; promoters should be morally committed to their work. Promoters affirm their obligation to share all techniques and knowledge that they have acquired with other peasant farmers. This is characteristic of the farmer-to-farmer approach in which the promoter becomes aware of the wider social impact of his or her knowledge.
Principle 2 is also an important feature of VGG efforts because promoters teach that management should be decentralized to the lowest appropriate level to encourage greater efficiency, effectiveness and equity.
Accordingly, promoters and farmer clients should continue to cultivate their own lands. Neither the promoter nor the client should lose his or her identity as a farmer. Instead, they should remain connected to the livelihood practices of the rural community and aware of the local needs for assistance. The promoter is considered an example for other peasant farmers and should be visible in this capacity as a role model.
Relevance to the Programme of Work on Agricultural Biological Diversity
Besides adaptive management, the principal strength of VGG with respect to the FAO/CBD collaborative programme is capacity building. The latter includes strengthening the ability to manage biological diversity (including soil biodiversity) and promoting responsibility. To this end VGG members have elaborated mechanisms to promote awareness and maintain continuity in their actions over time.
Promoters must work as unpaid volunteers in order to demonstrate their community commitment. They work several days a week for one or two years, receiving only travel expenses. During this period, they are evaluated according to their management of a specialty area, their willingness to participate responsibly in group endeavours and their ability to work as part of a team. If a promoter is subsequently asked to stay on with the group, he or she will receive a small monetary compensation for his/her participation.
Outcomes
VGG promoters have trained more than 2000 peasant farmers in Mexico and elsewhere in Latin America in integrated crop and soil biological management, and soil and water conservation practices, during the past two decades. Members of the group also count the following as some of their principal successes:
Lessons learnt
The successes of the Vicente Guerrero Group highlight the importance of farmer-to-farmer approaches in achieving sustainable crop production, soil conservation and soil biological management on marginal and degraded lands. Furthermore, they suggest that intangible factors are as important as technical capacity.
These include:
A Case Study from Africa - Bam Province, Burkina Faso4
Problem statement
To restore the productive capacity of crusted soils in the Sahel region of Africa in order to extend arable lands and sustain viable, agricultural livelihood systems.
Soil degradation, particularly crusting, is a major agricultural problem in the Sahelian region of Africa. The combined effects of extreme and difficult climatic conditions, over-grazing and trampling by cattle, continuous cultivation and other unsustainable management practices have resulted in the pervasive spreading of bare, infertile soils. Degraded soil structures and sealed crusts impede water infiltration and root growth, thus delaying soil regeneration and seriously limiting the use of local lands for crop and animal production. Because degraded soils constitute a serious threat to Sahelian agriculture, active restoration efforts must be undertaken if rural livelihoods are to be maintained.
Termites are widespread and abundant in tropical dry areas such as the Sahel. Although they are major agricultural pests, termites can also play an important role in recovering degraded ecosystems. Specifically, the burrowing and feeding activities of termites can be utilized to break up crusted soils and thereby counteract land degradation.
Objectives
The main purpose of this work was to evaluate the capacity of termites to improve the structure of crusted soils, including their ability to reduce soil compaction, increase soil porosity and improve the water infiltration and retention capabilities of soils. Such conditions encourage root penetration, vegetative diversity, and the restoration of primary productivity, all prerequisites for food and livelihood security in the Sahel.
Actors and activities
Organic mulch (cow manure or straw) was applied to soil surfaces during a three years study in order to trigger termite activity. It was assumed that termite-mediated processes (see above) would promote the recovery and rehabilitation of degraded soils. Dr. Abdoulaye Mando (Institut de l’Environnement et des Recherches Agricoles, Burkina Faso) completed this work as part of his PhD requirements under Drs. Leo Stroosnijder and Lijbert Brussaard (Wageningen Agricultural University, Holland).
Application of the ecosystem approach to soil biodiversity management
Three important principles of the ecosystem approach (CBD COP Decision VI/5) are evident in this case study. First, Principle 10 advises flexibility in balancing the goals of conservation, sustainable use, and agricultural production. Flexibility, in this case, allowed the negative impacts of termites to be turned into positive benefits for soil productivity because termites, widely considered to be pests, eventually enhanced agricultural production:
Principle 9 recognizes that cyclical or successional change is normative, dynamically stable, and ultimately resilient. Thus, ecological change should be incorporated into adaptive management plans. Adaptively working with ecological change was important to this study because:
Termite disturbance (seasonal or successional burrowing, excavation, and foraging) turned out to be a viable management option. Specifically, investigators found that:
A third component of the ecosystem approach also characterized this work. Principle 6 states that ecosystems should be managed within their functional limits; or more specifically, that management objectives should be conceived within the environmental and biological conditions that limit natural productivity. Such considerations were evident in this study, as investigators realized that:
Termite activity and weather can impose functional limitations on nutrient cycling in semi-arid, Sahelian conditions. For these reasons, it was acknowledged that:
Relevance to the Programme of Work on Agricultural Biological Diversity
In addition to adaptive management, the principal strength of this case study is its technical assessment of the goods and services, positive and negative impacts, and management options associated with termites as soil mixers, nutrient transporters and productivity enhancers (see above).
Outcomes
The principal outcome of this study was that termites successfully restored crusted Sahelian soils when their soil mixing and decomposing activities were properly managed by careful organic matter additions.
Lessons learnt
Perhaps the most important lessons learned from this study in Burkina Faso are that:
Furthermore, this case illustrates a potentially extremely important, practical and cost-effective way of using biological activity to restore seriously degraded and unproductive lands. Its practical application should be seriously investigated through participatory processes including on-farm experimentation and pilot project development.
A Case Study from Asia - Tamil Nadu, India5
Problem Statement
To restore soil fertility and increase tea yields on intensively cultivated tea plantations in southern India.
Between the 1950s and the 1980s, fertilizer and pesticide use in India increased tea production from 1000 to 1800 kg ha-1. Currently, national yields have stagnated as decades of intensive cultivation have left soil fertility greatly depleted. On some tea plantations, not even the use of external inputs and plant growth hormones has overcome 100 or more years of intensive exploitation.
Soil degradation on tea plantations is seen in: 1) the loss of soil biota (losses as high as 70 percent), 2) decreased organic matter, 3) lower cation exchange capacity, 4) reduced water retention, 5) soil compaction, 6) soil erosion, 7) nutrient leaching, 8) aluminium toxicity, 9) accumulated toxins (polyphenols) from tea leaves, and 10) acidification (pH levels as low as 3.8).
Objectives
The purpose of this study was to restore soil fertility and improve tea production on six private teas estates in Tamil Nadu, India, using organic matter and earthworms.
Actors and activities
Prof. Patrick Lavelle (Institut de Recherche pour le Développement; IRD) and Dr. Bikram K. Senapati (Sambalpur University, India) worked in collaboration with plantation managers from Parry Agro-Industries Ltd. In this effort, tea prunings, high quality organic matter, and vermicultured earthworms were applied in trenches between tea rows in order to evaluate effects on tea yields. Improvements in structural and biological properties of soils were expected to produce higher tea yields.
Application of the ecosystem approach to soil biodiversity management
Trenching is an old practice that has been mostly abandoned on plantations because of high human labour costs and substitutions by other techniques. In this study, it was thought that trenches would minimize soil loss and improve moisture and aeration conditions, so that nutrient cycling processes would be enhanced. The choice of trenching, an unconventional technique, illustrates Principle 11 of the ecosystem approach; that all forms of relevant knowledge (including traditional, indigenous and scientific) should be considered in developing management strategies. Interestingly, trenching, prunings, organic material and earthworms between tea rows (Bio-Organic Fertilization, or FBO6) dramatically increased yields and profits:
The surprising results of FBO soil biological management are a reminder that agro-ecosystems should be managed within their unique biological and economic contexts; a point clearly made by Principle 4 of the ecosystem approach. Principle 4 emphasizes that economic policies tend to undervalue sustainable agricultural practices, favouring instead a series of high-input/high-energy technologies suited to less diverse production systems. Nevertheless, results achieved with FBO demonstrate that even intensive agriculture, such as that practised on commercial tea plantations, can benefit from adaptively managing soil biodiversity (Principle 9).
Principle 8 addresses one of the interesting features of FBO soil biological management encountered in this study. More specifically, it addresses the fact that yields and profits with FBO varied considerably between the six different tea plantations. In particular:
These findings illustrate that varying temporal scales and lag-effects characterize agro-ecosystems and favour long-term, rather than short-term management solutions, a point aptly made by Principle 8.
In this study, project participants understood that variable yields indicated different degrees of land degradation and that long-term management commitments would be required to remedy these conditions. In particular, it was acknowledged that trenches at FBO sites would have to be opened and re-inoculated every three to four years in order to maintain high-level benefits.
Relevance to Programme of Work on Agricultural Biological Diversity
This case study addresses the need to identify technical assessments and adaptive management methodologies. In this respect, it determined that Bio-Organic Fertilization (FBO) is an affordable tool, adaptable to situational needs and appropriate to commercial management scales from small farms to plantations. The major components of this technological package include:
In addition, mainstreaming concerns are addressed in this study, as FBO has received patent protection and is now being disseminated within the agricultural sector. Mainstreaming activities include:
Outcomes
The principal outcomes of this case study were:
Lessons learnt
The salient lessons learned during this project were:
A Case Study from South America – Paraná, Brazil7
Problem to be solved
To improve yields of the common bean on nitrogen-poor, tropical soils in Brazil.
Brazil is currently the second largest producer of the common bean (Phaseolus vulgaris L.) in the world. However, inadequate inoculation technology and low soil fertility (especially in relation to nitrogen content) are limiting national yields. In 2001, 4.3 million hectares were sown with this leguminous crop, yet an average yield of only 640 kg ha-1 was harvested nation-wide; an amount considered poor by experts.
Nitrogen fixing rhizobia (a bacterial soil component associated with legume roots) might cost-effectively provide enough nitrogen to increase bean yields. However, inoculations with commercially available rhizobial strains have shown poor results and raised doubts about the viability of this approach as a management option. Poor inoculation results may be attributable:
Objectives
The main emphasis of this study was to improve root nodulation and nitrogen fixation in the common bean through inoculations with soil bacteria. The strategy chosen was to isolate and select efficient native rhizobia from local bean production sites.
Actors and activities
Mariangela Hungria (Embrapa-Soya, Brazil), Diva de Souza Andrade (Instituto Agronômico do Paraná, Brazil) and Iêda Carvalho Mendes (Embrapa Cerrados, Brazil) coordinated efforts to collect local rhizobia in the state of Paraná during 1992 and 1993. More than 400 isolates were tested for nitrogen-fixing capacity, competitive ability, and other characteristics appropriate for performance in the tropics.
Application of the ecosystem approach to soil biodiversity management
It was thought that efficient native strains might perform better as inoculants than commercial strains. In particular, some indigenous strains might remain genetically stable in stressful tropical environments, when compared to commercial rhizobia, and thus better able to fix nitrogen. Also, superior local rhizobia should competitively exclude symbiotically inferior local strains for nodulation sites.
Principle 6 of the ecosystem approach indicates that agro-ecosystems should be managed within the local environmental conditions that limit productivity. In this study, stressful conditions of cultivated tropical soils (e.g. high temperature, acidity and dryness) were major deterrents to root nodulation and nitrogen fixation, and had to be overcome in the development of an effective inoculant. Eventually, three strains (PRF 35, PRF 54 and PRF 81) functioned well under tropical conditions. These strains were characterized by high nitrogen fixation rates, good competitive ability and tolerance to high temperatures.
Principle 4 addresses the need to manage ecosystems in an economic context. In this case, the directive was to improve bean yields using native rhizobial inoculants because the alternative technologies were considered to be economically less viable. Specifically, commercial strains were known to be metabolically ineffective, resulting in low yields; and nitrogen fertilizers, the other option, contaminated ground water (at substantial cost because of impacts on biological diversity and human health).
After field testing, the superior performance and economic advantage of the PRF 81 inoculant was confirmed.
It was also determined that re-inoculation the following year improved the establishment of PFF 81. This practice was accordingly incorporated into management recommendations.
Another strain selection programme was started in 1998 for the Brazilian Cerrados region, an edaphic type of savannah. After three years of experiments, the H 12 and H 20 strains were selected as superior.
Another brief, but important result of this study relates to the ecosystem approach. Principle 3 urges agro-ecosystem managers to consider the impacts of management interventions both within and beyond the boundaries of the managed system. It is noteworthy that:
The selection of superior native strains from local bacterial diversity did not require genetic modification or the introduction of exotic species. The actual and potential risks of genetically altered micro-organisms and non-native strains in field situations have been hotly debated for decades. However, the use of locally selected rhizobia avoids these risks altogether, while assuring higher bean yields and associated economic gains.
Relevance to the Programme of Work on Agricultural Biological Diversity
The thematic focus of this case study with respect to the joint programme falls within technical assessments. In particular, this effort represents an innovative approach to improving inoculation responses that seldom considers the isolation and assessment of efficient strains from local sites of bean production. It is an approach that is worthy of replication in other tropical agricultural areas around the world.
Outcomes of activities
One of the most important results of this study was the official recommendation of PRF 81 as a commercial Brazilian inoculant in 1998. This recommendation was based, in part, on its superior performance in tropical soils. In particular,
This positive performance has resulted in increased inoculant use in Brazil and encouraged the identification of other genetically stable, competitive and efficient bean rhizobia from tropical areas.
Lessons learnt
This research and development effort has demonstrated that a concerted programme of strain selection in local bean cropping areas produces economically viable inoculants. If this approach is followed around the world, it might help improve poor yields and nitrogen depletion that plague tropical areas.
A case study from South America - Paraná, Brazil8
Problem to be solved
Physical disturbance is one of the principal causes of biodiversity loss in all world ecosystems. Soil macrofauna (invertebrates important for soil structure, function and fertility) are also susceptible to physical disturbances, especially those associated with tillage practices. Adapting tillage and planting regimes to minimize disturbance should provide better environments for soil macrofauna and their functions, thus benefiting sustainable agriculture.
Soil macrofauna are large invertebrates (termites, ants, earthworms, true bugs, snails, millipedes, centipedes, spiders and other arachnids, crickets, beetle grubs and other insect larvae) that spend all or a portion of their life cycle in the soil. Their activity is essential to the physical, chemical and biological integrity of soils, and important for soil fertility. Soil macrofauna include:
However, biological diversity around the world is susceptible to physical environmental disturbances, and soil fauna populations, activity and diversity can be reduced by repeated physical disturbances associated with conventional tillage (especially when pesticides and other agro-chemicals are also used). For this reason, it is believed that minimal disturbances to agro-ecosystem soils should provide better environments for soil macrofauna and their functions than conventional tillage regimes.
Objectives, actors and actions
Because of the importance of understanding physical disturbance in agro-ecosystems, several experiments were begun in 1979 in several locations in Southern Brazil, to compare no-tillage (NT) and conventional tillage (CT) practices in terms of long-term trends in productivity, nutrient use, carbon inputs, decomposition rates and soil conservation. In 1998, soil macrofauna comparisons were added to the sampling protocol at NT, CT and minimum tillage sites.
The work was undertaken by researchers (and students) of various institutions: George Brown, Lenita Oliveira and Eleno Torres of Embrapa-Soybean; Norton Benito and Amarildo Pasini of the Universidade Estadual de Londrina; and M. Elizabeth F. Correa and Adriana M. de Aquino of Embrapa-Agrobiologia. Several private farm owners participated.
Application of the ecosystem approach to soil biodiversity management
Sustainable ecosystems depend upon balanced biological interactions among a diversity of organisms. The same is true for soil ecosystems. However, in the latter, organismal diversity and biological activity are more strongly regulated by C availability than in other ecosystems.
Soil organic carbon (SOC) is derived primarily from the decomposition and recycling of dead plant and animal material. Its transformation is carried out principally by soil organisms. In natural ecosystems, these carbon transformations (represented by inputs and outputs) are generally balanced over time, but in agro-ecosystems, the amount and quality of SOC can be sharply reduced by tillage disturbances. SOC depletion is especially a problem in exposed tropical soils, where high temperatures and rainfall can drive nutrient cycles at great velocities and leaching can quickly reduce available nutrients in the system.
There is an important relationship between soil disturbance, SOC and soil biodiversity (including macrofaunal diversity).
In this case study, the comparison of disturbance characteristics associated with NT and CT practices, as well as their respective abilities to conserve soil macrofauna, demonstrates Principles 3 and 5 of the ecosystem approach. Principle 5 recognizes that the sustained functioning and resilience of ecosystems depend on conserving relationships among diverse and interacting species. Thus, management objectives should modify or substitute any practices that seriously limit functioning. Principle 3 acknowledges that management interventions, such as tillage, can have undesirable effects on soil organisms and their functions. Careful consideration and analysis are required to avoid negative impacts.
Results showed that NT systems generally improved soil environmental conditions for plants and soil animals compared to CT systems. Improvements (see Table 1) included reduced erosion, enhanced nutrient- and water use-efficiency by crops, and improved crop yields and profitability, especially after a transition period of a few years.
NT practices also increased soil macrofaunal diversity, according to several indicators, and speeded population recovery after the cessation of CT practices. Soil organisms (Table 1) that especially benefited from NT were natural predators (important for the biological control of pests), bioturbators (important for improving soil physical structure) and decomposers (important for recycling plant residues).
Finally, the lack of soil disturbance at NT sites led to increased soil OM in the top-most soil layers, increased protection of the soil surface with plant residues and increased populations of beneficial soil invertebrates, despite the soil compaction that often accompanies NT methods.
Nevertheless, the authors of this case study felt that more detailed research was necessary to properly link the increase in diversity and abundance of selected groups of soil macrofauna in NT with the improvement and maintenance of soil functions (e.g. water infiltration, soil aggregation, soil protection, decomposition, nutrient cycles, carbon sequestration, pest control, plant growth and yields) that are critical to the sustainability of NT systems.
This case study briefly touches upon themes relevant to Principle 12, that the ecosystem approach should involve as many relevant sectors of society as possible. In other words, it should be a multi-stakeholder approach. After 30 years of implementation in Brazil, NT practices have gained wide acceptance by farmer associations, cooperatives, researchers and extension agents, agroindustry leaders and agricultural policy makers.
Providing that economic benefits of utilizing NT methods and conserving soil macrofauna are also realized, it is likely that this stakeholder support network will rapidly disseminate and adopt a wide array of soil biological management practices amenable to NT systems.
TABLE 1
Some agro-ecological and economic consequences of adopting NT practices
PARAMETER MEASURED |
PARAMETER MEASURED |
Erosion |
Greatly reduced |
Compaction |
Generally increased |
Soil C stocks |
Increased in upper layers |
Productivity |
Equal or higher, esp. in dry years |
Predators
(bio-control) |
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Saprophages
(decomposers) |
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Bioturbators |
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Pests |
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Macrofauna Diversity |
Greater |
Taxonomic Richness |
Greater |
Relevance to the Programme of Work on Agricultural Biological Diversity
In terms of adaptive management, it is very likely that NT practices, when combined with the use of cover crops in rotations, will be highly compatible with new and existing techniques for the conservation of soil macrofauna and the sustainable use of their ecosystem functions. The potential synergy between these management objectives deserves special attention by investigators and managers; it is highly relevant to the future success of sustainable agriculture.
As discussed above, there is a potential for forming extensive capacity-building partnerships in Brazil to simultaneously promote NT methods and soil macrofauna conservation. This possibility is based upon the compatibility of some of their management goals, and the existing level of coordination among current NT stakeholder groups. Nevertheless, proven techniques and economic benefits from direct soil macrofauna management remain to be demonstrated, and this will ultimately determine acceptance by farmers and other stakeholders in Brazil.
Outcomes
A notable outcome of this study was the growing confidence that:
Lessons learnt
The principal lessons learnt from this case study were that:
A case study from Queensland, Australia9
Problem to be solved
Yield decline of sugarcane is a widespread problem throughout the Australian sugar industry. It results from loss of productive capacity of soil under long-term monocultures of sugarcane, with lack of rotations, excessive tillage of the soil at planting and severe soil compaction from the use of heavy machinery during harvesting. Collectively, these management practices have led to soils that are low in organic C and cation exchange capacity, have a high bulk density and a low microbial biomass. This in turn is associated with a build-up of populations of detrimental soil organisms, which affect the growth and health of the sugarcane root system.
Actors and activities
Sugarcane is a major Australian crop earning AUS$ 11 billion (US$ 0.7 billion) in export income in 1999. It is produced on some 450000 hectares of land along the coast of Queensland and northern New South Wales and in the Ord River valley in Western Australia. In 1993, a multi-disciplinary research programme, known as the Sugar Yield Decline Joint Venture, was established among concerned institutes (see authors and institutes cited above) to investigate the causes of sugarcane yield decline and develop solutions to revive a viable, productive and sustainable sugar industry.
Conventional sugarcane management
In most sugarcane-growing districts sugarcane is grown largely as a monoculture and is normally harvested 12-18 months after planting. The next or first-ratoon crop is produced from the buds remaining on the underground portions of the stalks. Normally four or five ratoon crops are produced before the stool (rootstock) is ploughed out. Traditionally, a 4-6 month fallow (either bare, as weeds or a sown legume) was applied before the cycle was repeated. However, since the early 1970s a system of plough-out/re-plant has been increasingly practised, resulting in virtually no fallow period. This increased intensity has been accompanied by more extensive use of inorganic fertilizers, insecticides and herbicides.
It has also been accompanied by green cane harvesting in many areas, in place of the more traditional burnt cane harvesting, and by the use of heavy machinery to harvest and transport the cane. Whilst these changes have increased the efficiency of cane production they have also been associated with the development of a plateau in cane production in the sugar industry over the period 1970-1990. This is thought to be due to a combination of factors including climate, the growth of cane on poorer quality soils, widespread introduction of mechanical harvesting and intensification of the monoculture system.
Effects of conventional sugarcane practices on soil health and yield
In regard to the long-term impact on soil health, it was recognized as early as 1930 that cane growth on suitably prepared virgin land often out-yielded that on old cane land (i.e. under cane for several years), and that cane growth in old cane land was improved following soil pasteurization. There was a growing recognition that a combination of management factors-monoculture, inappropriate use of inorganic fertilizers, heavy harvesting machinery-has led progressively to the development of soil physical, chemical and biological properties that constrain plant growth. This catalyzed the establishment in 1993 of a multi-disciplinary research programme, the Sugar Yield Decline Joint Venture, to investigate the causes and develop solutions. It was clear that a holistic “ecosystem approach” was necessary to address the yield decline problem.
Research on the physical, chemical and biological properties of soils under monoculture cane revealed the extent to which the soils have become degraded under the current cane management system, affecting the health of the sugarcane root system. Whilst not consistent in magnitude across all sites, the soils under cane monoculture were characterized by having high bulk density, low available water, low labile organic carbon, low pH, low CEC, high exchangeable Al and Mn and low Cu and Zn.
Microbial biomass was also seen to be rapidly reduced after the introduction of sugarcane to new land. Plant growth responses to pasteurization or fumigation and fungicides were accompanied by a significant improvement in the health of the cane root system, implicating the role of detrimental soil organisms, such as pathogenic soil fungi and plant parasitic nematodes, in yield decline. Pachymetra root rot (P. chaunorhiza) has been associated with significant yield losses in plant and first-ratoon crops and has been controlled largely through selection of resistant cultivars. Pythium species (P. arrhenomanes, P. myriotylum and P. graminicola) have also been shown to be pathogenic towards sugarcane. A possible detrimental effect of arbuscular mycorrhizal fungi (AMF) on yield decline has been suggested, though not yet demonstrated, in view of the relatively high use of phosphate fertilizers by the Australian sugar industry. More than 30 pest species of nematode have been associated with sugarcane roots in Australia including five plant-parasitic species: lesion nematode (Pratylenchus zeae), root knot nematode (Meloidogyne javanica), stubby root nematode (Paratrichodorus minor), spiral nematode (Helicotylenchus dihystera) and stunt nematode (Tylenchorhynchus annulatus). From studies P. zeae and M. javanica are considered to cause the most root damage. Yield responses of 10-50 percent were obtained across the sites when nematicides were applied to plant and ratoon cane crops.
Management practices to reduce the effects of detrimental soil biota on yield decline
Until recently, research into detrimental soil biota associated with sugarcane yield decline has provided few viable options for cane growers. The selection of cane varieties resistant to Pachymetra root rot has been successful but has had only a minor impact on yield decline, most likely because other fungal root pathogens have occupied that niche. Similarly, the use of fungicides to control known and unknown pathogenic fungi or nematicides and the lesion and root knot nematode would be considered uneconomic or environmentally unsustainable by both the industry and the wider community. Such treatments would also reduce populations of beneficial fungi and nematodes in the soil. More sustainable options centred on changing the current cane management system are therefore required to address the problem. Such options include the incorporation of rotation breaks and the more general use of organic amendments in the cropping system. Other options focus on reducing tillage and compaction of the soils during the planting and harvesting operations in order to reduce damage to soil structure and to improve water infiltration. Each of these options has the potential to contribute substantially to improving soil physical and chemical properties and hence influencing the balance between beneficial and detrimental organisms in the soil.
In this case study, recognition was made of Principles 3 and 5 of the ecosystem approach: Principle 3 acknowledges that management interventions, such as tillage, can have undesirable effects on soil organisms and their functions; Principle 5 recognizes that the sustained functioning and resilience of ecosystems depend on maintaining a dynamic relationship and restoring interactions among diverse and interacting species and their environment. Thus negative impacts of different practices on soil functioning were identified and analyzed with a view to adapting and testing improved management options. Moreover, in addressing the problems of productivity and sustainability of the sugarcane industry with stakeholders, it directly addresses Principle 4 of the ecosystem approach: Recognizing potential gains from management, there is usually a need to understand and manage the ecosystem in an economic context. Understanding that economics tends to override sustainable agricultural practices, the aim was to identify viable alternatives to the conventional monoculture and high-input system through diversification and the management of natural agro-ecological interactions.
Rotation breaks
Rotation breaks as a means of breaking disease cycles and for improving soil fertility have generally not been considered a viable option by the Australian sugarcane growers for economic reasons. These include pressure from the sugar mills for a constant and high volume of cane for processing, perceived economic losses associated with taking land out of cane production for a short period, lack of evidence of perceived benefits from a break crop, and the lack of suitable rotation crops. Efforts were therefore made to explore more fully the benefits of rotation breaks to cane production and soil health. Trials were established at five sites in Queensland on land under cane monoculture for at least 20 years, incorporating three different breaks, varying from 9 to 42 months, under a sown legume/grass pasture (e.g. a mixture of Brachiaria decumbens and Arachis pintoi), alternative crops (soybean, peanut, maize) and a bare fallow (kept free of weeds with glyphosphate) and control plots. Each of the breaks gave substantial increases in cane yield (average of 33 percent across all five sites) that were comparable to that achieved following methyl bromide fumigation of monocultured cane soil.
It was seen that significant yield responses could be achieved with both a pasture and a bare fallow break despite the fact that these breaks had contrasting effects on soil properties. The observed rotation response following the pasture and crop breaks was probably due to a combination of soil fertility factors in addition to a reduction in detrimental soil organisms. A build-up of suppressive micro-organisms in the soil under the pasture break and the increase in populations of free-living bacterial- and fungal-feeding nematodes under the pasture and crop breaks are indicative of a shift towards a more balanced soil biology in these systems. These nematodes are beneficial to plant growth through their role in nutrient cycling and in regulating organic matter decomposition; they are commonly regarded as an indicator of the biological status of the soil. There appeared to be considerable scope for improvement of the biological status of monocultured cane soils in addition to the removal of known specific root pathogens.
Organic amendments
Green cane harvesting is now practised widely throughout the Australian sugar industry. This generally results in the return of 10-15 tonnes (dry weight)/ha of cane trash to the soil surface after each harvest. More than 80 percent of the C in this trash is lost through respiration during the following year, although considerably more of the trash N is retained. Evidence suggests that while there are measurable increases in microbial biomass and organic C in the top 0-5 cm of soil under green cane trash blanketing there is no evidence that this counteracts yield decline. This may be partly due to the intensive soil cultivation prior to establishing a new crop, which accelerates erosion of microbial biomass and oxidation of organic C.
A number of sugar mill by-products such as filter mud and boiler ash are commonly applied to the soil prior to establishment of a new sugarcane crop. These products are valued for their capacity to improve soil nutrient status of the soil (N, P, Ca, Mg, Si, K, Cu and Zn) but it is not known if they have any impact on detrimental soil biota in sugarcane in Australia. Though the many reports of successful use of compost and other organic materials to suppress fungal and nematode pathogens in other crops suggests that appropriate organic amendments could have beneficial effects on detrimental soil organisms associated with sugarcane yield decline.
Tillage
Under long-term sugarcane monoculture, characteristic poor soil structure and widespread compaction are due to a combination of intensive cultivation, use of heavy machinery during harvesting, often under wet conditions, and a mis-match of crop row spacing and machinery wheel spacing. Soil compaction has been shown to reduce water infiltration and soil hydraulic conductivity in sugarcane soils, and together with frequent damage to the sugarcane stool during harvesting, contributes to yield decline. To counter these problems, strategic tillage techniques based on minimum cultivation and the use of herbicides to remove the old sugarcane stool in the row at re-planting, coupled with maintenance of compacted inter-rows during the crop cycle, have been developed. These techniques are shown to have no adverse effect on cane yields but offer cane growers significant savings in fuel and machinery costs.
There is a traditional belief that tillage of the soil between sugarcane cropping cycles has beneficial effects in terms of controlling root diseases and pests. This may be true with some root feeding pests such as the canegrub (species of Antitrogus, Dermolepida, Lepidiota and Rhopaea). However, the deployment of biopesticide products (e.g. those containing the fungus Metarhizium anisopliae - a natural biological control agent of the canegrub) may be more effective in a minimum tillage situation. The premise is that natural biological control systems will have a greater chance of developing if tillage is kept to a minimum, though little is known about the effects of minimum tillage practices on soil organisms associated with sugarcane yield decline.
Strategy for promoting uptake of improved management practices
For raising awareness of impacts of management practices among cane growers and bringing about changes in the sugarcane industry, soil health report cards are being used. These monitor changes in soil properties using a minimum set of seven indicators of soil fertility and quality and illustrating effects of improvement from legume-cane rotations, organic matter management and minimum tillage: reduced nematodes and diseases, improved soil structure and increase in beneficial disease-suppressive organisms. This is backed up by an information and communication strategy and demonstrations and field trials of best management practices (see www.landcareresearch.co.nz).
This process addresses Principle 12 of the ecosystem approach recognizing the need to involve all relevant sectors of society and scientific disciplines. Through the Sugar Yield Decline Joint Venture, the cane growers, representatives of industry, and various land and water, crop protection, sugar and farming systems research bodies, are directly involved in the soil health reporting and analysis. Their views and suggestions are taken into account in the development of the most appropriate soil and crop management system. Research is continuing on certain aspects with a view to enhancing adoption, such as the duration of the rotation break required to achieve a significant benefit and the longevity of the benefit from the break: important economic considerations for cane-growers.
Summary
In order to circumvent yield decline and improve productivity and long-term sustainability, major changes to the sugarcane cropping system need to be promoted. Efforts are ongoing to promote adoption of a legume-based rotation break at the end of the cropping cycle to reduce populations of detrimental biota, particularly nematodes, and to help restore soil fertility (e.g. N), supplemented by the incorporation of organic amendments prior to planting, in view of their beneficial impact on soil biota. Adoption of minimum tillage and controlled traffic practices to increase the capture of potential benefits from green cane harvesting and to reduce the amount of soil subjected to compaction are also encouraged.
CASE STUDY: 1 FARMER-TO FARMER METHODS CAN PROMOTE SOIL AND AGRICULTURAL BIODIVERSITY
Vicente Guerrero Group with 20+ years of success
CONTINENT, COUNTRY, AND STATE OR REGION |
PROBLEM TO BE SOLVED |
OBJECTIVES |
ACTORS |
RELEVANCE TO 12 CBD ECOSYSTEM PRINCIPLES |
RELEVANCE TO 4 AREAS OF FAO WORK PROGRAMME |
OUTCOMES |
LESSONS LEARNT |
North America |
Poor soil quality, quantity and biological diversity on degraded lands |
To promote integrated crop, soil and soil biological management through farmer-to-farmer methods |
Farmer-to-farmer promoters from local community |
P1- sharing of benefits equitably
|
Adaptive management |
More than 2000 farmers in Mexico and Latin America have been trained in agro-ecological principles and practices during more than 20 years |
Long-term success in crop and soil management depends more upon shared values and local conviction, than on technological trends, which can change rapidly |
CASE STUDY: 2 MANAGING TERMITES AND ORGANIC MULCH CAN INCREASE SOIL PRODUCTIVITY
Severely crusted soils are restored
CONTINENT, COUNTRY, AND STATE OR REGION |
PROBLEM TO BE SOLVED |
OBJECTIVES |
ACTORS |
RELEVANCE TO 12 CBD ECOSYSTEM PRINCIPLES |
RELEVANCE TO 4 AREAS OF FAO WORK PROGRAMME |
OUTCOMES |
LESSONS LEARNT |
Africa |
Restore soils in order to extend arable lands and increase productivity |
To manage termites and local organic matter to rehabilitate crusted soils |
Academic researchers and their institutions |
P6- functional constraints |
Technical assessments |
Termites can be highly beneficial agents whose soil mixing and decomposing activities can be managed by organic matter additions in order to enhance soil productivity. |
Soil structure degradation results from eradicating native soil organisms (termites). Applying surface OM feeds termites and promotes their regenerativeactivities. |
CASE STUDY: 3 MANAGING EARTHWORMS AND ORGANIC MATTER CAN IMPROVE CROP AND SOIL PRODUCTIVITY
Renewal of soil fertility, even at sites of intensive agriculture
CONTINENT, COUNTRY, AND STATE OR REGION |
PROBLEM TO BE SOLVED |
OBJECTIVES |
ACTORS |
RELEVANCE TO 12 CBD ECOSYSTEM PRINCIPLES |
RELEVANCE TO 4 AREAS OF FAO WORK PROGRAMME |
OUTCOMES |
LESSONS LEARNT |
Asia |
Rehabilitate plantation lands degraded by decades of intensive tea cultivation |
To restore soil fertility and improve stagnant tea yields using soil fauna and local organic matter |
Agro-industry representatives, farm managers and academic researchers and their institutions |
P4- economic context |
Technical assessments |
A practical, economical, and conservation- minded solution to soil degradation Patented methods that are being mainstreamed world-wide as Bio-organic fertilization (FBO) |
FBO must be tailored to each site and needs the regular attention of trained personnel, FBO best suited for countries with inexpensive and readily available labour force |
CASE STUDY: 4 SYMBIOTIC NITROGEN FIXATION WITH THE COMMON BEAN CROP
|
CONTINENT, COUNTRY, AND STATE OR REGION |
PROBLEM TO BE SOLVED |
OBJECTIVES |
ACTORS |
RELEVANCE TO 12 CBD ECOSYSTEM PRINCIPLES |
RELEVANCE TO 4 AREAS OF FAO WORK PROGRAMME |
OUTCOMES |
LESSONS LEARNT |
|
South America |
Improve low bean crop yields on nitrogen-poor, tropical soils |
To improve common bean response to nitrogen-fixing soil bacteria |
Academic researchers and their institutions |
P3- impact of interventions |
Technical assessments |
Common beans inoculated with competitively superior, native Rhizobia produce high yields in nitrogen-poor, tropical soils |
Superior strains of Rhizobia can be selected from the diversity of the native soil bacteria with no need for genetic modifications |
CASE STUDY: 5 NO-TILLAGE AGRICULTURE BENEFITS SOIL MACROFAUNA
CONTINENT, COUNTRY, AND STATE OR REGION |
PROBLEM TO BE SOLVED |
OBJECTIVES |
ACTORS |
RELEVANCE TO 12 CBD ECOSYSTEM PRINCIPLES |
RELEVANCE TO 4 AREAS OF FAO WORK PROGRAMME |
OUTCOMES |
LESSONS LEARNT |
South America |
Restore and maintain soil fertility on severely eroded agricultural lands |
To provide the best environment for macrofauna and their soil fertility functions |
Private farm owners with academic researchers and their institutions |
P3- impact of interventions |
Adaptive management |
NT systems provided better conditions for macrofauna than CT systems |
NT can help re-establish soil fauna after CT disturbances |
CASE STUDY: 6 MANAGEMENT PRACTICES TO IMPROVE SOIL HEALTH AND REDUCE EFFECTS OF DETRIMENTAL SOIL BIOTA ASSOCIATED WITH YIELD DECLINE OF SUGARCANE IN AUSTRALIA
CONTINENT, COUNTRY, AND STATE OR REGION |
PROBLEM TO BE SOLVED |
OBJECTIVES |
ACTORS |
RELEVANCE TO 12 CBD ECOSYSTEM PRINCIPLES |
RELEVANCE TO 4 AREAS OF FAO WORK PROGRAMME |
OUTCOMES |
LESSONS LEARNT |
Australia |
Widespread sugarcane yield decline under monocultures with excessive tillage and soil compaction by heavy machinery |
Adapt practices to improve crop growth and soil health increase soil OM and CEC increase activity of beneficial soil organisms for fertility and soil structure and reduce detrimental soil organisms |
The Sugar Yield Decline Joint Venture involves the canegrowers, representatives of industry and various land and water, crop protection farming systems and sugar research bodies. |
P4- understand and manage the
ecosystem in an economic context |
Adaptive management of soil-crop system and practices |
Industry promoting uptake and monitoring of better practices: legume-based rotation break; OM; minimum tillage to enhance positive/reduce negative effects of soil biota restore soil fertility+structure |
Unsustainable practices in agro-industry can be trans-formed into sustainable and productive systems |
1 See Convention on Biological Diversity (CBD), Decision V/6 of the Conference of the Parties (COP), the Appendix on the Ecosystem Approach.
2 See in particular CBD COP Decisions III/11, V/5 and VI/5.
3 Adapted from F. J. Ramos S. (1998) Grupo Vicente Guerrero de Españita, Tlaxcala. Dos décadas de promoción de campesino a campesino. Red de Gestión de Recursos Naturales and Rockefeller Foundation, Mexico City, Mexico
4 Adapted from Abdoulaye Mando (1997) The role of termites and mulch in the rehabilitation of crusted Sahelian soils. Tropical Resources Management Paper 16. Wageningen Agricultural University. Wageningen, the Netherlands, 101 pp.
5 Bikram Keshari Senapati, School of Life Sciences, Sambalpur University, Orissa State, India; Patrick Lavelle, Institut de Recherche pour le Développement, Bondy, France; Pradeep K. Panigrahi, Parry Agro-industries, Ltd., Tamil Nadu; Sohan Giri, State Pollution Control Board, Bhubaneswar; and George Brown, Embrapa Soja, Londrina PR Brazil.
6 Fertilisation Bio-Organique dans les Plantations Arborées, Patent ref. No PCT/FR 97/01363
7 Mariangela Hungria, Embrapa Soja, Londrina, PR, Brazil; in collaboration with Rubens J. Campo, Júlio Cezar Franchini and Lígia M. O. Chueire, Embrapa Soja, Londrina, PR, Brazil; Ieda C. Mendes, Embrapa Cerrados, Planaltina, DF; Brazil; Diva S. Andrade, Arnaldo Colozzi-Filho and Élcio L. Balota, IAPAR, Londrina, PR, Brazil; Maria de Fátima Loureiro, UFMT, Cuiabá, MT, Brazil
8 George Brown, Embrapa-Soja, Londrina, PR Brazil, in collaboration with Lenita Oliveira, and Eleno Torres of Embrapa-Soja; Norton Benito and Amarildo Pasini, Universidade Estadual de Londrina; M. Elizabeth F. Correa and Adriana M. de Aquino of Embrapa-Agrobiologia.
9 Prepared from a paper by C.E. Pankhursta, R.C. Magareyb, G.R. Stirlingc, B.L. Blaird, M.J. Belle and A.L. Garsidef, based on the Sugar Yield Decline Joint Venture,
a CSIRO Land and Water, Davies Laboratory,
Aitkenvale, Queensland 4814, Australia
b Bureau of Sugar Experiment Stations,
Tully, Qld 4854,
c Biological Crop Protection, 3601 Moggill Road, Moggill,
Qld 4070,
d Queensland Department of Primary Industries, Tully, Qld
4854,
e Farming Systems Institute, Queensland Department of Primary
Industries, Kingaroy, Qld 4610,
f Bureau of Sugar Experiment Stations, Davies Laboratory, Aitkenvale, Qld 4814.
