No-till with Stylosanthes guianensis cover crop affects weed community and improves weed management in upland rainfed rice in Madagascar
2023
Rafenomanjato, Antsa | Ripoche, Aude | Marnotte, Pascal | Letourmy, Philippe | Autfray, Patrice | Randriamampianina, Jean Augustin | Barberi, Paolo | Moonen, Anna Camilla
In Madagascar, upland rainfed rice is traditionally grown on tilled soil without transplanting. Weed infestation by annual species is a serious issue in such a system. Stylosanthes guianensis, a legume cover crop, can be grown with rice as a living mulch but its effect on the weed community and rice yield was not yet well studied. Therefore, a field experiment was conducted in Mid-West Madagascar from 2016 to 2018. A no-till system with stylosanthes (NT) managed as a living mulch was compared to the conventional tilled (CT) system. Two fertilisation regimes were included: organic manure (F1) and organic manure combined with mineral fertiliser (F2). Weed floristic surveys were performed, and weed harmfulness evaluated by comparing weedy and weed-free plots. The living mulch harmfulness was evaluated using weed-stylosanthes-free plots. Results showed that NT suppressed dominant grass weeds Digitaria spp. and Eleusine indica leading to a decrease in total weed biomass. Rice yield was significantly higher in NT than in CT; in weed-free condition, it was 2.4 versus 2 t ha−1 in NT and CT, respectively, and 1.5 versus 0.6 t ha−1 in NT and CT, respectively, in weedy condition. The living mulch reduced rice yield by 14% but it remained significantly higher in NT than in CT. The addition of mineral fertiliser to the organic manure had a positive effect on rice yield but only in weed-free conditions. This study showed that a no-till system with a living mulch can help to control the most competitive weeds without undermining rice production.
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