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Summary Ecosystem services have received increasing attention in life sciences, but only a limited amount of quantitative data are available concerning the ability of weeds to provide these services. Following an expert focus group on this topic, a systematic search for articles displaying evidence of weeds providing regulating ecosystem services was performed, resulting in 129 articles. The most common service found was pest control and the prevailing mechanism was that weeds provide a suitable habitat for natural enemies. Other articles showed that weeds improved soil nutrient content, soil physical properties and crop pollinator abundance. Weeds were found to provide some important ecosystem services for agriculture, but only a small number of studies presented data on crop yield. Experimental approaches are proposed that can: (i) disentangle the benefits obtained from ecosystem services provisioning from the costs due to weed competition and (ii) quantify the contribution of diverse weed communities in reducing crop competition and in providing ecosystem services. Existing vegetation databases can be used to select weed species with functional traits facilitating ecosystem service provisioning while having a lower competitive capacity. However, for services such as pest control, there are hardly any specific plant traits that have been identified and more fundamental research is needed.

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The role of farms in landscape evolution : a major driving factor of ecological dynamics. The agricultural landscape mosaic results from the distribution of land use, and types of field margins and hedgerows management, within farms. The mosaic structure shows forms of organization linked to internal farms functioning, but that express on other spatial levels than fields and farms. To make clear these mechanisms, we simulate the effects of a change in agricultural policies through two scenarios, with only taking territorial management within farms for rules. The resulting landscapes differ by the hedgerow network, the nature and degree of fragmentation of land cover units, at different spatial levels. The example of two species of contrasted modes of space utilization (mobility and use of resources), shows the importance of taking into account those levels, to relate agricultural and ecological processes for analysing their interactions.

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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