Organic agriculture relies on cultivars bred for high-input environments, or uses landraces with lower yields. In the DIVERSOW project we are holistically assessing the reduced input benefits of incorporating landrace material, whilst keeping the higher yields of elite cultivars.
Conventional crop production systems are optimised for high yield and economic sustainability. These systems depend on a high level of fertilisers and chemical inputs, which has cascaded into a number of environmental problems.
Organic farming systems replace these inputs through more environmentally sustainable alternatives. However, most crop cultivars available today are optimised for conventional crop production systems, where it is expected that nutrients are abundant and interference by pests, weeds, and diseases is minimal. They therefore underperform in organic systems where nutrient inputs are usually lower and interference by pests, diseases and weeds is greater, resulting in the commonly observed yield gap. One factor in this observed underperformance is the limited genetic diversity of modern crop cultivars, which hinders their adaptability to organic systems. In this way, a monoculture of a modern cultivar is more vulnerable to interference than a genetically diverse system.
Older (heritage) cultivars and landraces (locally-adapted crop populations) are more genetically diverse, with a broader spectrum of characteristics, but typically lower yield potential. Heritage cultivars and landraces may benefit an agricultural system through their adaptability to changing environmental conditions, and their resilience to weeds, pests and diseases. They have, however, been underutilised in crop production systems to date; their benefits suggest great potential for diversified cropping systems where modern cultivars and landraces are mixed, either within one species- ‘mixed cropping’, or with another species as an intercrop, to maximize the benefits they provide.
Up to now, the effects of increased genetic diversity and impact on crop yield, nutrition and resilience to biotic stressors have been studied in isolation. It is recognised that a more holistic approach is required to consider the effects that different cropping systems and their agroecology can have on interspecific interactions in field conditions, but evidence is limited, especially in organic systems. Therefore, by building on previous research findings, our novel project seeks to holistically examine the interrelationships between different functions and their impact on yield in organic systems.
The goal of DIVERSOW is to identify added benefits of increased crop diversity for producers in an organic agricultural system, and unravel the ecological mechanisms by which they could be provided. Our key hypothesis is that increasing intra- and inter-crop genetic diversity brings multiple agroecological-orientated benefits to an organic system, specifically increasing suppression of dominant weeds, repulsion and suppression of insect pests, and inhibition of pathogens.
Photo: Göran Bergkvist
To address this hypothesis, this project will use a holistic approach to assess three levels of diversity; individual cropping, mixed cropping, and intercropping (with faba bean). Within this there will be further levels of diversity by moving from individual cultivars to landrace populations. The holistic manner of this project is achieved by examining the interference of weeds, fungal diseases, and insect herbivores, to indicate differences in crop defence among these treatments, together with the Nutrient uptake, plant health, and root system, and how these interact with each other and the final crop yield. This will take place over two field seasons (2024 & 2025) across two regions in Sweden (Uppland and Skåne).
We envision that the findings of this investigation will inform potential approaches to addressing the yield gap in organic farming by exploiting the benefits of increased crop diversity. These results will be disseminated both to stakeholders and the scientific community to stimulate the adoption of organic agriculture.
The project group consists of five early-career researchers from the Department of Crop Production Ecology at SLU, with a diverse range of interlinking skills and perspectives: Darwin Hickman will contribute to weed and allelopathy assessments and overall project coordination, James Ajal will contribute by evaluating nutrient use efficiency, Fede Berckx will work on the fungal disease and community analysis, Jonathan Cope will contribute to the growth & root system assessment and fungal disease analysis, and Eirini Daouti will contribute to collection and analysis of pest, natural enemy, weed seed, and aphid predation data.
Project leader/principal investigator: Darwin Hickman
Funder: This project is funded in large part by the Ekhagastiftelsen 2023 research grant.