Speaker
Description
Introduction. Pea (Pisum sativum L.) is a key diversification crop but current pea varieties are not very competitive against weeds. Intercropping pea with cereals is a promising lever to reduce weed infestation and damages. However, past pea varieties were bred for sole crops usually in herbicide-protected fields. They may not be optimal for growing in intercrops with wheat and in the presence of weeds. The objective of this study was to identify, depending on the type of cropping system and weed flora, (1) the key pea parameters that drive crop production and weed control in pea when intercropped with wheat (Triticum aestivum L.), (2) optimal combinations of pea and wheat parameter values as well as intercrop management techniques (tillage, sowing date and density, interrow width…), to maximise these goals.
Material & Methods. Virtual experiments were run, using FLORSYS (Colbach et al., 2021). This mechanistic individual-based 3D model simulates daily crop-weed seed and plant dynamics over the years, from the cropping system and pedoclimate, focusing on plant-plant competition for light. The model includes five winter pea and three winter wheat varieties. Virtual varieties (5 pea and 10 wheat) were created by randomly combining variety-parameter values according to a Latin Hypercube Sampling (LHS) plan, respecting parameter ranges and correlations observed in the actual varieties. A global sensitivity analysis was run, using another LHS plan to combine pea and wheat varieties, crop rotations and management techniques in nine contrasting situations (e.g., conventional vs organic, no-till, type of weed flora). Simulated data were analysed with classification and regression trees (CART). Additional simulated data with sole-crop winter pea instead of pea-wheat intercrops were taken from Colbach et al. (2022).
Results. Intercropping reduced pea yield loss due to weeds (by 30% for the least weed-tolerant varieties, e.g. Enduro) and field infestation (by 14% for the least weed-suppressive varieties, e.g., 886-1). In wheat-pea intercrops, intercrop management and the pea variety were more influential than the wheat variety for yields. Yield loss due to weeds and field infestation depended mostly on the management of intercrops and other crops of the rotation, with little effect of variety parameters.
We highlighted (1) key pea parameters that drive potential (weed-free) yield and competitivity against weeds (e.g., biomass allocation to leaves until full maturity, increased plant width per unit biomass when shaded, frost tolerance). These are pointers for breeding varieties that regulate weeds in intercrops by better competing for light; (2) Rules to guide farmers to choose the best pea variety, depending on the production goal, the intercropped wheat variety and the cropping system (Figure 1). Pea and/or intercrop yields as well as weed suppression improved when pea ideotypes were tailored to cropping system types (e.g., always tilled vs never tilled), and combined with optimal wheat varieties and crop management (e.g., ideotypes y12 and y3 vs gy1-gy3). The best pea ideotypes had a small root system and prioritised above-ground plant growth and light interception, except in no-till where a large superficial root system left less soil moisture for superficial weed seeds (NT1 and NT2). Pea ideotypes based on CARTs searching for the best weed-infested pea or intercrop yield also produced the best weed-free yields and weed suppression (e.g., gy1-gy3 vs gp1-gp2, Y1 and Y23 vs P12 and P3 or F2). Contrasting pea ideotypes could achieve similar performances, if the associated wheat varieties and/or crop management rules were optimised (e.g., P12 vs P3). In summary, a high pea yield in weedy intercrops required a pea variety with a high yield potential combined with a weed-suppressive wheat variety and weed-preventive management.
Perspectives. The present pea-parameter rules provide guidelines for farmers to choose their pea varieties in cereal-legume intercrops and for breeders to screen existing germplasm collections and to identify traits for which the select during breeding.
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)
References
Colbach et al. (2021) Field Crops Research. https://doi.org/10.1016/j.fcr.2020.108006
Colbach et al. (2022) Frontiers in Plant Science doi.org\10.3389/fpls.2022.809056
| Keywords | legume-cereal intercrops; weeds; ideotype; biological regulation, simulation model |
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