Five benefits of...
Intercropping is the practice of growing a mixture of crop species, either spatially within a field (be it using structured rows of alternating crops or unstructured mixtures of multiple species), or temporally within a cropping season (for example, by relay).
Dr Jennifer Banfield-Zanin has used the CHAP Field-Scale Precision Equipment, in recent projects to explore the benefits and drawbacks of intercropping using clover living mulches or ‘green manures’, whereby strips within an area of established clover are tilled and drilled with a cash crop. These include the EU-funded DIVERSify and TRUE projects and RPA-funded Living Mulches project, featuring trials carried out at Stockbridge Technology Centre (STC).
Based on that experience, Dr Banfield-Zanin, in collabotation with CHAP Technical Liaison Officer Lucy Plowman, presents the top five benefits of intercropping:
This is arguably the main, and most important benefit, not only for farmers, but for the environment, biodiversity and the battle to achieve net zero.
Intercropping can help farmers to actively improve soil health. Having a variety of root structures improves both soil drainage and the infiltration of nutrients and water, through physical disturbance of the soil to differing depths and architectures.
Species with strong tap roots, such as certain clover species or lucerne (alfalfa), help to break up areas of soil compaction, while plants with branching fibrous root systems, such as cocksfoot grass, can be useful improvers of soil crumb structure. In green manure systems, root structures can bind soil particles together, and help prevent loss of topsoil via erosion or run-off.
Diverse root systems in turn support a diverse and thriving micro- and macro-biological population belowground, enhancing organic matter decomposition and turnover, and releasing nutrients for root uptake. Increased organic matter content also has great benefits to soil structure, increasing aggregate formation and the amount of water the soil can retain. Altogether, these intricately linked mechanisms can be kickstarted into a positive feedback loop by increasing in-field plant diversity.
Harnessing a leguminous partner within an intercropped system, such as through the use of clover living mulches, allows for better nitrogen management in the field. Legumes can naturally increase nitrogen availability in the soil through biological nitrogen fixation, reducing the need for artificially applied nitrogen to feed the cash crop. This can help support gross margins and buffer against market changes.
Nitrogen losses can also be reduced, as a diverse mix of species maximizes nitrogen usage across the soil profile, preventing harmful leaching of unused nitrogen into water courses. Living mulches can also help prevent nitrogen leaching, which can occur when soils are left bare. These improvements to soil fertility have led to nitrogen-fixing legumes being a key companion crop of choice for farmers beginning to explore intercropping, through pairing beans, peas, or clovers with cereal and other crops.
Increasing the species diversity of plants in the field, by even just one additional species, can reduce the abundance and severity of weed, pest, and disease pressures the crop is exposed to. Increased ground cover, as would be expected with clover living mulches, can help crowd out competitive weed species, with weed biomass reductions shown repeatedly in trials including those using the precision strip-tillage equipment at STC. Increased diversity in the plant canopy can disrupt pest behaviour by making target crops harder to locate, and can impede dispersal of fungal spores and slow the spread of some plant pathogens across a field.
Improved species richness can also indirectly reduce pest numbers by attracting and supporting a greater diversity in natural enemies of pests, including parasitoid wasps, predators such as ladybirds and hoverflies, as well as spiders and ground beetles. More resources are also available for pollinators, which are crucial to productivity and maintaining overall healthy agroecosystem function. There can also be knock-on benefits to farmland bird and small mammal populations. By promoting overall biodiversity, these gains can support the achievement of agrobiodiversity policy goals, and may help unlock financial support as part of environmental management schemes.
By potentially reducing the need for nitrogen fertiliser, fungicide, herbicide and insecticide inputs, a transition to intercropping systems can help contribute towards overall lower synthetic inputs. This can be a key advantage for farm businesses: less money spent on inputs increases the gross margin and therefore profitability, which is especially important in light of chemical fertiliser market pressures and the changing regulatory landscape. Not only this, reduced inputs are also important in alleviating environmental pressures from chemical pollution of soil, water and air, and the subsequent harm to biodiversity and potentially human health.
Improvements to soil health and nitrogen management, the suppression of damaging pests, weeds and diseases, and reductions in synthetic input requirements all contribute towards overall productivity and biological system resilience on-farm, and help buffer against market pressures. Species-rich systems have been shown to be better able to mitigate against unexpected abiotic and biotic stresses, such as new invasive pests, extreme rainfall patterns or disease outbreaks initiated by changing temperatures. This can help reduce the risk of complete crop failures, and subsequent profit losses. Growing a mixture of cash crops in the field also diversifies income and can buffer against unpredictable market fluctuations, further adding to the resilience of the farm business.
Although research has shown that species-rich intercropped systems have the potential to increase crop yields compared to an equivalent monoculture, thereby boosting profits, the technique can also bring significant challenges associated with competition between species for light, space, and nutrients. Although this inter-specific competition can negatively impact productivity, Precision Agriculture Technology and novel machinery are becoming readily available for farmers to use to overcome this. Tools such as the CHAP strip-till cultivator based at Stockbridge Technology Centre, and precision inter-row Cameleon seed drill based at Newcastle University, can help mitigate against potential yield penalties when intercropping, and support farmers in exploring the possible benefits that can be realised from transitioning to a diverse, species-rich cropping system.