Speaker
Description
In 2021, the agricultural sector accounted for 18.4 % of French GHG emissions in which 29 % was associated with crop fertilization (Citepa, 2023). Consequently, the reduction of synthetic fertilizers is a key element to lower agricultural emissions.
In south-western France, durum wheat (Triticum durum) is an important crop both in terms of area and contribution to the economic performance of local arable farms. In conventional farming, durum wheat is fertilized at a relatively high rate to maximize yield and guarantee quality, mainly linked to grain protein content. Agroecological approaches relying more on ecosystem services like diversification with longer rotations including legumes crops and multi-services cover crop (MSCC), were tested in the Syppre network to lower mineral nitrogen rates and associated GHG emissions (Longis et al., 2024). We hypothesized that these levers, combined with the use of a decision-tool (CHN) capable of considering the benefits of diversification for the fertilization recommendations, would make it possible to significantly reduce mineral nitrogen rates on durum wheat without reducing yield or quality.
A 7-year field experiment was carried out at the Syppre experimental platform of Lauragais in southwestern France from 2017 to 2023 (Longis et al., 2024). This study compares the durum wheat of two modalities:
- Reference cropping system (2-year rotation): durum wheat - sunflower, without any cover crop, representative of the dominant crop rotation in Lauragais, with optimized cropping practices to ensure high technical and economic performance.
- Innovative cropping system (8-year rotation): MSCC and chickpea – oilseed rape intercropped with MSCC – durum wheat – MSCC and sorghum – winter pea and buckwheat (as cash crop or MSCC according to biomass produced) – durum wheat – MSCC and sunflower – winter wheat.
N fertilizer rates were calculated using the balance method for the reference durum wheat and using the CHN crop model (Soenen et al., 2019), whose aim is to simulate crop growth in real time to better adapt fertilizer doses, for the durum wheats in the innovative system.
On average of all years, mineral nitrogen available at the end of winter in innovative durum wheats was superior to the reference (21 kg N ha -1, P < 0.15) ; Durum wheat N fertilisation was reduced by 69 kg N ha -1 (P < 0.05) in the innovative system compared to the reference ; Grain yields were non significantly different with 6.5 and 6.7 t ha -1 for the innovative and reference durum wheats respectively; grain protein content were always equal or above the quality threshold for both modalities.
Mineral fertilizer costs were significantly reduced in the innovative system, but this did not offset the costs of MSCC-certified seed and increased herbicide costs we also observed.
Our results show that greater diversification can help to significantly reduce nitrogen fertilization and the associated risks of pollution and illustrate the importance of using decision tools to make the most of the benefits of diversification.
The presentation will detail the analyses on mineralisation rates between the two modalities, the effect of climate on the indicators observed, the change in herbicide use and discuss the appropriation of the results by local farmers.
Citepa, 2023. Gaz à effet de serre et polluants atmosphériques. Bilan des émissions en France de 1990 à 2022. Rapport Secten éd. 2023.
Longis, S., Cadoux, S., Toupet de Cordoue, A.-L., Tauvel, P., Estienne, M., Onzon, P., Lescourret, F., Rouillon, C., & Aubertot, J.-N. (2024). Performance of innovative cropping systems diversified with oilseeds and protein crops: identification and resolution of methodological issues, using the Syppre experimental network as a case study. OCL, 31, 2. https://doi.org/10.1051/ocl/2023022
B. SOENEN, M. BONNEFOY, C. DELPECH, B. PIQUEMAL, P. DESCAZEAUX, F. DEGAN, F. LAURENT, 2019. Mise au point du pilotage intégral de l’azote avec le modèle de culture CHN : approche « CHN-conduite ». Agronomie, Environnement & Sociétés, vol.9, numéro 1.
| Keywords | rotation extension ; legumes ; multi-services over crop ; CHN crop model |
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