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Poster De Conférence Année : 2018

Cropping systems for driving biological regulation of weeds. A simulation study of seed predation by carabids

Laurène Perthame
Sandrine Petit
Nathalie Colbach

Résumé

Weed seed predation by carabid beetles (Coleoptera, Carabidae) may contribute to weed control in crop fields but to date, evidence of weed regulation by carabids is scarce. Predation rates are driven by several factors (crop management techniques, habitat quality, pedoclimate, and carabids’ seasonal dynamics). Models are needed to evaluate the impact of weed seed predation on multi-annual weed dynamics, and thus on crop production and weed biodiversity. We developed a predation model which was added to an existing weed dynamics model (FlorSys, Colbach et al., 2014). The model was built from available literature and experimental data. It simulates the effects on daily predation rates of management techniques, vegetation cover, climate, carabids’ intra-annual abundance variation and in-field weed seed preferences of carabids. First, a sensitivity analysis of predation to model parameters was run to identify the parameters that have the most impact on predation rate and are thus required to be accurately estimated. Then, ten cropping systems were simulated over thirty years to evaluate the impact of weed seed predation on weed dynamics, crop production (weed biomass, yield loss due to weeds) and biodiversity (weed species richness, bee food resources). The systems were based on a rapeseed/wheat/barley rotation, differing in rotational crop diversity, herbicides use, ploughing and tillage frequency. The sensitivity analysis revealed that predation rate was the most sensitive to cropping system. Management techniques must thus be set carefully in order to promote predation, regardless of parameters value. Predation rate varied greatly with parameters associated to effects of temperature and incident radiation whereas it varied little with parameters associated to carabid seasonal dynamics and effect of management techniques (insecticides, tillage, plough). The former parameters must be estimated precisely whereas current values can be kept for the latter. The cropping system simulations showed that annual predation rates varied greatly among years, depending on the crops. Predation rates averaged over the thirty simulated years were higher in cropping systems including spring crops (pea or sunflower). Adding seed predation by carabids in the simulations only marginally changed multiannual weed dynamics. Effects of predation on crop production and weed biodiversity were rare and depended on the cropping system. Predation decreased weed species richness in all ten cropping systems because the model assumed that carabids predated their preferred weed species rather than the most frequent ones. Consequently, we plan to make seed predation also depend on seed density in a future model version. We will also simulate a wider range of cropping systems to conclude on the contribution of seed predation by carabids to the biological regulation of weeds. Funding: INRA and the CoSAC project (ANR-15-CE18-0007).
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Dates et versions

hal-02733678 , version 1 (02-06-2020)

Identifiants

  • HAL Id : hal-02733678 , version 1
  • PRODINRA : 466922

Citer

Laurène Perthame, Sandrine Petit, Nathalie Colbach. Cropping systems for driving biological regulation of weeds. A simulation study of seed predation by carabids. ESA 2018 XV European Society for Agronomy Congress, Innovative cropping and farming systems for high quality food production systems, Aug 2018, Genève, Switzerland. , 2018. ⟨hal-02733678⟩
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