Speaker
Description
Introduction.
Management of perennial weeds has become increasingly difficult with the reduction of herbicide use. Perennials accumulate reserves in belowground storage organs from which they can regenerate new plants after a disturbance. Tillage is a key lever to control perennial weeds because it destroys the aboveground part and fragments the belowground storage organs, stimulating the regrowth of new shoots that use and thus reduce the reserves. Field studies suggest that the tillage tool’s features influence perennial-weed control. However, the underlying mechanisms of these effects need to be further investigated, especially the fragmentation of perennial storage organs by tillage tools. The objectives of this study were to 1) analyse how different tools fragment the creeping roots of Cirsium arvense (L.) Scop, one of the most problematic perennial species in arable crops, 2) combine existing knowledge in a predictive model to identify and rank the most important factors driving post-tillage regeneration of perennial weeds from fragments of their storage organs.
Material & Methods.
A field trial was conducted in Dijon in 2022-2023 to sample C. arvense root fragments left in the soil after single passages by five contrasting tillage tools (mouldboard plough, rotary harrow, chisel plough, horizontal cultivator and disc harrow). The fragments were measured and the distribution of root-fragment lengths was analysed for each tool with regard to their features (blade type, power take-off drive and working depth). By combining the results of this experiment and data from literature on the other processes involved, a model for predicting the regeneration rate of perennial weeds after tillage from fragments of their storage organs was built. Regeneration was successful when the belowground shoot produced by a fragment was long enough to emerge. The model was applied for different scenarios combining two tillage tools, two soil structures, two storage-organ distributions in the soil, two soil temperatures, two fragment diameters and two levels of maximal shoot length per unit fragment biomass (Figure 1).
Results.
In the experiment, the distribution of fragment lengths varied with tillage tool: rotary harrow left the smallest and least variable fragment lengths (3.7 cm on average), mouldboard ploughing the largest and most variable ones (12.7 cm on average and up to 30 cm). The three other tools produced intermediate-sized fragments (8-10 cm on average).
According to the model, fragment diameter and maximal shoot length per unit fragment biomass were the main determinant of regeneration rate: fragments were 32% (respectively, 29%) more likely to regenerate when their diameter (respectively, their maximal shoot length) doubled. The choice of the tool also had a significant impact: there were 13% less regenerated fragments after a rotary harrow than after a mouldboard plough. Soil structure and storage-organ distribution in the soil had a minor impact while soil temperature had no impact.
Discussion.
The length distributions of C. arvense root fragments depending on the tools were consistent with the scarce previous work (Leblanc & Lefebvre, 2018). The important role in the model of fragment weight and maximal shoot length in regeneration was in line with previous work on emergence (Torssell et al., 2015) and highlighted that the regrowth potential of perennial species are key drivers which need to be investigated further. Finally, the model showed differences between the tools: rotary harrow induced a lower regeneration rate from fragments than mouldboard plough, which was probably linked to a higher fragmentation rate (Bergkvist et al., 2017). However, to compare the overall effect of different tillage tools on perennial-weed control, the present model needs to be supplemented with formalisms predicting the regeneration rate of the unfragmented storage organs, located below the tillage depth.
Funding.
French Ministries in charge of Ecology, Agriculture, Health and Research
ANR PPR BeCreative (ANR-20-PCPA-0001)
COPRAA funded by the Office Français de la Biodiversité (OFB)
References.
Bergkvist et al. (2017). Control of Elymus repens by rhizome fragmentation and repeated mowing in a newly established white clover sward. Weed Research. https://doi.org/10.1111/wre.12246
Leblanc, M., & Lefebvre, E. M. (2018). Impact de différents outils de travail du sol sur le système racinaire du chardon et du laiteron. https://irda.blob.core.windows.net/media/5365/leblanc-lefebvre-2018-impact_de_differents_outils_de_travail_du_sol_sur_le_systeme_racinaire_du_chardon_et_du_laiteron.pdf
Torssell et al. (2015). Modelling below-ground shoot elongation and emergence time of Sonchus arvensis shoots. Acta Agriculturae Scandinavica. https://doi.org/10.1080/09064710.2015.1044463
| Keywords | perennial-weed regeneration; tillage tool; storage-organ fragmentation; predictive modelling; Cirsium arvense; creeping-root fragments |
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