The intensification of monocultures has led to the degradation of soil systems worldwide, but the emergence of intercropping practices may provide a key alternative to restabilizing sustainable food production.
Simple Guide to Intercropping | How to Grow More Food in your Vegetable Garden
Transformations in agricultural practices and the rise of monocultures
The rapid acceleration of population growth has led to an associated increase in food demand, in turn requiring more areas of arable land to farm systems and higher productivity from existing ones. In response, agricultural production has focused on implementing largescale monoculture systems of key crops.
However, the intensification of monocultures has led to the degradation of soil health, water, and air quality issues due to nitrate, phosphorous, and pesticide runoff as well as leaching, higher greenhouse gas emissions, and thus an overall reduction in the sustainability of farming systems.
To limit such negative impacts, farmers have gradually reimplemented the concept of intercropping. Despite having existed since the evolution of agriculture, this practice is returning although it remains limited to small operations in developing nations.
Defined as the cultivation of two or more crops together in the same field for a period of time, intercropping offers key benefits to soil and crop quality and offsets the issues associated with monocultures.
Intercropping, therefore, capitalizes on the mutualistic and beneficial relationships among different crops, harnessing the ecological processes of niche differentiation to ensure the higher quality and sustainability of crop production.
Previous studies have found this practice increases productivity and provides greater ecosystem services, and can be applied across many environmental conditions, soil types, and crop combinations.
The benefits of intercropping as an alternative to monocultures
In a 2020 chapter on the benefits of intercropping, Samantha Glaze-Corcoran et al., discussed the trade-offs associated with culturing methods, demonstrating that intercropping generates higher yields per land unit than monocultures, and also provides a reduced risk of crop failure, and greater resilience to market fluctuation
Authors then review the common types of intercropping, various methods of economic assessments as well as ecosystem services and environmental benefits of intercropping, highlighting the efficient use of natural resources that intercropping provides.
Moreover, the review also advocates that intercropping increases overall system biodiversity, manages pests, and in many instances, enhances crop productivity and quality alongside better natural soil fertility with reduced consumption of off-farm inputs.
Nonetheless, monoculture remains the dominant cultivation strategy, and authors emphasize the need for further research to improve the fundamental understanding and precise manipulation of intercropping systems to provide applicable strategies as alternatives to monocultures.
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Types and functions of intercropping systems
To date, intercropping has been further subdivided into four main types that offer similar but varying benefits depending on crop types, environment, and objectives.
First, mixed intercropping consists of the proximate and simultaneous growth of two or more crop types without spatial arrangement, allowing for crops to be seeded and harvested together and separated after harvest.
Second, strip intercropping is a system of parallel strips of crops each made of rows of different crops. Strips are therefore spatially arranged and need to allow for harvesting space as well as inter-crop interactions.
Third, similar to strip cropping, row intercropping differs only as one of the crop types are planted in single or double rows beside the other, allowing for higher interspecific interaction. This can promote shading, root mingling, and competition for water and nutrients. This strategy in particular is gaining traction due to its beneficial effects across crops including disease suppression.
Finally, relay intercropping combines strip and intercropping planting arrangements by cultivating two or more different species simultaneously but crops are planted and harvested at different times. This system also allows for spatial arrangements in strips or rows, and is unique due to the opportunity for coordination between crop life cycles, allows for isolated growth before crop interaction, and also provides a recovery period for the second crop type once the first is harvested.
Each strategy emphasizes different elements of intercropping, with varying levels of crop interaction, but challenges are also key to consider. For instance, spatial allocation of strip intercropping or the fact that relay cropping requires an advanced understanding of the effectiveness in planting different crop types, present important technical management considerations.
These issues were further discussed in a review by Anne Bybee-Finley and Matthew Ryan from 2018, who highlighted the required to develop standardized methodologies across intercropping systems and to establish common criteria to facilitate cross-study comparisons.
The review also discussed the common forms of intercropping with what crop types, showing perennial crops are favored over annual plants, and that intercropping has advanced in recent decades particularly with cover crops, which has progressed the field of research greatly.
Future directions for intercropping in the face of global climate change and increased food demand
The advent of global climate change has exacerbated the growing insecurity related to food production, with crop yields expected to decline in the future despite the rise in food demand. Intercropping plays favorably into such scenarios due to its benefits relating to maintaining sustainable production systems whilst not compromising the environment.
Moreover, recent studies have further improved the outlook of implementing intercropping more widely by developing systems with higher nitrogen-fixing crops such as legumes, a practice known for a long time, but has gained more attention in recent years as it is an alternative to fertilizer use to alleviate some of the anthropogenic stressors on agricultural systems.
The study, published by Erik Steen Jensen and colleagues in 2020, focused on the global scale of intercropping to reduce fertilizer usage using intercropped nitrogen-fixing crops and cereals instead.
The researchers estimated that the increased nitrogen use efficiency in intercropping can reduce the requirements for fossil-based fertilizer nitrogen by about 26% on a global scale, adding that if all current grain legume sole crops would instead be intercropped with cereals, this would provide a saving of arable land that can be used.
The study concludes that crop diversification by intercropping can reduce global requirements for synthetic fertilizer and support the development of more sustainable cropping systems and further research into how different intercropping can be used to counteract or mitigate the impacts of global climate change may prove increasingly valuable.
Nonetheless, although diversifying farming systems provides ecological benefits and thus enhances sustainability and resiliency of agriculture, challenges remain particularly relating to management complexities and economic costs. This is due to the fact farmers may incur short-term losses in intercropping, but this effect can be avoided using subsidies.
Future progress on improving the accessibility to precision agriculture and intercropping as well as the feasibility of broad adoption of intercropping in developed nations will be particularly insightful in the transition away from monoculture systems.
- Bybee-Finley, K., & Ryan, M. (2018). Advancing Intercropping Research and Practices in Industrialized Agricultural Landscapes. Agriculture, 8(6), 80. doi: 10.3390/agriculture8060080
- Glaze-Corcoran, S., Hashemi, M., Sadeghpour, A., Jahanzad, E., Keshavarz Afshar, R., Liu, X., & Herbert, S. J. (2020). Understanding intercropping to improve agricultural resiliency and environmental sustainability. Advances in Agronomy, 199–256. doi: 10.1016/bs.agron.2020.02.004
- Jensen, E. S., Carlsson, G., & Hauggaard-Nielsen, H. (2020). Intercropping of grain legumes and cereals improves the use of soil N resources and reduces the requirement for synthetic fertilizer N: A global-scale analysis. Agronomy for Sustainable Development, 40(1). doi: 10.1007/s13593-020-0607-x
- Tilman, D. (2020). Benefits of intensive agricultural intercropping. Nature Plants, 6(6), 604–605. doi: 10.1038/s41477-020-0677-4