Speaker
Description
Introduction. Intercropping – several species cultivated in the same field for a significant part of their growing periods – is a key lever for weed control. The aim of this study was to evaluate, by simulations with the FLORSYS model, the effects of bispecific legume–cereal intercrops on weed dynamics and their impact on crop production, tested in the absence of nitrogen or water stress.
Material and methods. This study simulated: (1) seven species proportions for wheat (Triticum aestivum L.)–faba bean (Vicia faba L.) and barley (Hordeum vulgare L.)–pea (Pisum sativum L.) mixtures (hence "species-proportion design"), and (2) nine spatial sowing patterns for triticale (Triticosecale)–faba bean, durum wheat (Triticum durum Desf.)–faba bean and wheat–pea mixtures (hence "sowing-pattern design"). In both cases, mixtures were compared to their corresponding sole crops (controls). Intercrops and controls were inserted into rotations and simulated over 30 years and repeated with 10 climate scenarios from Toulouse (South-Western France), either without weeds or with a high-density weed flora typical of the region. Weed management was organic-based or with reduced herbicide use. Simulations were run with FLORSYS, a mechanistic individual-based 3D model which simulates daily crop-weed seed and plant dynamics over years, from the cropping system and pedoclimate, focusing on plant-plant competition for light (Colbach et al., 2021).
Results. Simulations showed that, in the absence of weeds, the yield per plant in intercrops varied from 13% of the sole-crop yield (pea–wheat mixture in the species-proportion design) to 173% (triticale–faba bean mixture in the sowing-pattern design). In average, intercropping reduced weed-free yield per plant by 42% for legumes and had no effect for cereals. When weeds were included in the simulations, the average legume yield per plant decreased by only 24% compared to sole legumes, whereas the average cereal yield per plant decreased by 18%. In other words, the more competitive cereals protected legumes against weeds in intercrops but suffered more from weed competition than in sole cereals. Indeed, the weed biomass in intercrops was greater than or equal to that of the sole cereals, and less than that of the sole legumes (Figure 1.A and B). The intercrops that best controlled weeds were barley–pea and triticale–faba bean.
In presence of weeds, the spatial pattern alternating one cereal row with one legume row (50% cereal–50% legume) as well as the 67% cereal–33% legume and the 100% cereal–50% legume in the species-proportion design were those that both maximised yields of both legumes and cereals and minimised losses due to weeds (Figure 1. C and D). Additive designs were not more weed-suppressive than substitutive designs.
Conclusion and Perspectives. The present study highlighted the value of intercropping for weed management, and identified sowing proportions and sowing patterns depending on the objectives being pursued. In the presence of weeds, legumes benefitted more from intercropping than cereals because legumes are less competitive against weeds. This work will be extended to other species mixtures and management methods in order to better integrate farmers' practices and in contexts where water and nitrogen may be limiting. This work will thus contribute to help designing innovative cropping systems by integrating, among other things, the resilience of the systems designed in the face of climate change, using an agro-ecological approach to weed management.
Reference
Colbach, N., Colas, F., Cordeau, S., Maillot, T., Queyrel, W., Villerd, J., Moreau, D., 2021. The FLORSYS crop-weed canopy model, a tool to investigate and promote agroecological weed management. Field Crops Research 261, 108006. https://doi.org/10.1016/j.fcr.2020.108006
Funding
INRAE
European Union's Horizon 2020 Research and innovation programme ReMIX (N 727217)
Horizon Europe IntercropVALUES (N°101081973)
ANR PPR SPECIFICS (ANR-20-PCPA-0008)
ANR PPR MoBiDiv (ANR-20-PCA-0006)
COPRAA funded by the Office Français de la Biodiversité (OFB)
| Keywords | Intercropping; Weeds; Simulation model; Sowing pattern; Sowing density |
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