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Donald L. Books by Donald L. Trivia About Advances in Agron If they are, we need to then use our new understanding to design intercropping systems to account for them. Adopting an ecological approach to understand the underlying mechanisms will be central to achieving this goal. These examples consider mainly organismal interactions, but another critical aspect of the environment is its physical structure.
But small variations in microtopography can have important impacts by creating closely integrated but distinct niches, which in turn can enable species coexistence in crop systems. Opportunities clearly exist to manage the local variation in microtopography, and hence factors such as soil water status, to suit particular intercropping combinations.
Furthermore, as we unpick these relationships, we may be able to relate variation in key traits to microtopographic location, and hence better select for such traits when breeding for intercrops. As well as the proposal we made earlier for a flow of information from ecology relevant to the improvement of intercropping systems, in return — and as a brief aside — the study of intercropping could have important lessons for our understanding of natural and seminatural systems. Obvious questions arise as to whether mechanisms and processes underlying enhanced yield per unit area or sustainability in intercrops operate in natural systems.
For example, mechanisms that enhance soil mineral availability have been identified from intercropping systems, but these processes have not been examined in natural or seminatural systems.
A prime example of this is the potential for some species in alkaline soils — through acidification of the rhizosphere — to increase the availability of elements such as P and Fe, and hence the mineral nutrition of neighbouring plants see the earlier 2. To the best of our knowledge, this facilitation mechanism has not been explored in natural and seminatural plant communities, but could readily be operating. Furthermore, perhaps some of the key challenges in ecological science can be addressed by studying in detail the ecology of intercropping systems.
Ecologists have long struggled to understand the processes by which different combinations of plant traits enable species coexistence and regulate ecosystem function. Intercropping studies can tell us much about niche and trait complementarity, how different trait combinations can influence system function and sustainability, and how these effects might vary depending on the environmental context.
Both agronomy and ecology can clearly contribute to the improvement of intercropping systems. But to realize these benefits, major challenges for research remain. Some of them, for example breeding for intercrops, and understanding better the interactions between plants and other organisms in crop systems, have already been discussed. Here we propose briefly some other aspects of research that we feel could be important for the development of intercropping systems and their wider uptake.
Many studies have focused on particular processes rather than on the interactions between the multitude of processes that occur simultaneously in an arable system. Hence, it is difficult to identify limitations to major processes driving variation in yields or other ecosystem services generated by intercrops. However, true systems research is laborious and needs inputs from numerous disciplines to be effective.
This review article has brought together concepts from plant physiology, agronomy and ecology. More studies are needed to explore the potential of intercropping to deliver ecosystem services beyond crop production, including improving soil and water quality, improving landscape, controlling pests, and mitigating climate change. Ecosystem service approaches should emphasize that intercrops could achieve food security with reduced anthropogenic inputs and lower environmental impact.
Consideration of the wider suite of services and goods that can be supplied by intercropping could promote its use, but to achieve this we need more and better indicators of service delivery. What is critical, though, is achieving a balanced picture of the costs and benefits of intercropping and other alternative food production systems.
Could more diverse systems based on intercropping fare better? Whilst some of the mechanisms by which they deliver benefits are understood, there is considerable potential to improve intercropping systems to gain either greater yield or other benefits with the same inputs, or sustained yield with reduced inputs based on new knowledge from both ecology and agronomy, and the interface between the two disciplines.
In the short term, perhaps the most straightforward approach is simply to trial new combinations of crops to exploit beneficial mechanisms that have already been identified, for example, new combinations of cereals and legumes a widespread focus for current research. Rapid improvements are also possible through the development of new agronomic practices, including the mechanization of intercropping systems and improved nutrient management, but again such efforts can be taken forward using existing knowledge and experimental approaches.
However, breeding programmes should explicitly consider multiple traits that would benefit mixed cropping and not simply those traits known to raise the yield of monocrops. These breeding efforts, as well as the development of management practices tailoring intercropping systems to the local environment, can be guided by the new understanding derived from ecological research into organismal interactions.
Perhaps the most distant from immediate implementation are approaches based on more abstract concepts from ecology, including phylogenetic distance and coevolution. However, the apparent scale of these effects in some ecological studies indicates that they should at least be considered as part of the research agenda for improving intercropping systems: are such processes operating in intercropping systems, what are the scale of these effects, and how can we use this knowledge to guide our crop management or breeding practices?
Applying all of these approaches will need a better exchange of information among ecologists, environmental scientists, agronomists, crop scientists, soil scientists and ultimately social scientists e. Please note: Wiley Blackwell are not responsible for the content or functionality of any supporting information supplied by the authors. Any queries other than missing material should be directed to the New Phytologist Central Office.
Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries other than missing content should be directed to the corresponding author for the article. Volume , Issue 1. If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account. If the address matches an existing account you will receive an email with instructions to retrieve your username.
New Phytologist Volume , Issue 1. Research review Free Access. Rob W. Alison E. Tim J. Timothy S.
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Paul D. Pietro P. Hamlyn G. Alison J. Blair M. Robin J. Christine A. Philip J. Tools Request permission Export citation Add to favorites Track citation. Share Give access Share full text access. Share full text access. Please review our Terms and Conditions of Use and check box below to share full-text version of article. Summary Intercropping is a farming practice involving two or more crop species, or genotypes, growing together and coexisting for a time. Figure 1 Open in figure viewer PowerPoint. Figure 2 Open in figure viewer PowerPoint.
Facilitation, resource sharing and niche complementarity enable polyculture systems to yield more than their corresponding monocultures. Certain facilitative interactions can be associated with particular soil types either acid soils or alkaline and calcareous soils , and when present can be either strong solid lines or weak dashed lines. It is also apparent when plants acquire mineral elements in different chemical forms.
The net benefits are crop protection, pollination, greater photosynthetic carbon assimilation, greater acquisition of N, P, micronutrient and water, and sharing of these resources temporally to increase yield. Plant traits for resource acquisition and underlying mechanisms The physiological traits required by crops to maximize resource acquisition are identical in intercropping and monocropping systems, but the challenge of intercropping systems is how best to combine traits of different plants to improve overall performance.
Designing and breeding for intercropping systems Plant selection and breeding offer two approaches for improving intercropping systems that, to date, have rarely been considered. Applying ecological knowledge to intercropping systems Ecologically, we can define the processes occurring in intercropping systems as the negative interactions of competition, parasitism and amensalism, and positive interactions of mutualism and complementarity Odum, Figure 3 Open in figure viewer PowerPoint. Examples of recent developments in ecological research top row and their relevance to important goals for the improvement of intercropping systems middle row , leading to the final aim of improved intercropping systems as measured through a number of performance metrics bottom row.
In addition, ongoing ecological research has considerable potential to discover novel interaction processes, which could improve our understanding of trait complementarity or interaction context dependency, or could help us to improve intercropping systems in as yet unknown ways, as indicated by the dashed lines and arrows. Intercrops and microtopography These examples consider mainly organismal interactions, but another critical aspect of the environment is its physical structure. Future perspectives for intercropping research Both agronomy and ecology can clearly contribute to the improvement of intercropping systems.
Systems understanding of intercropping Many studies have focused on particular processes rather than on the interactions between the multitude of processes that occur simultaneously in an arable system. Intercropping and ecosystem services More studies are needed to explore the potential of intercropping to deliver ecosystem services beyond crop production, including improving soil and water quality, improving landscape, controlling pests, and mitigating climate change.
Supporting Information Please note: Wiley Blackwell are not responsible for the content or functionality of any supporting information supplied by the authors.
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Filename Description nphsupTableS1. Agroecologically efficient agricultural systems for smallholder farmers: contributions to food sovereignty. Agronomy for Sustainable Development 32 : 1 — Wiley Online Library Google Scholar. Google Scholar.