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RESEARCH PRODUCT

Experimental assessment of insect pollination on rapeseed yield and oil quality in farmer’s field demonstrates positive effect of pollinator richness

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EAGESTAD DOCT INRA; Pollination is an ecosystem service on which humans depends through its link to food production. Some crops, e.g. oilseed rape (Brassica napus L.), are pollinated by a broad range of insects such as by honeybees, wild bees, and hoverflies. According to experimental studies, oilseeds rape production can be increased by 10-50% by insect pollination, however these results are often obtained by comparison between presence-absence of pollinators not with pollinators gradients. Moreover, no study has investigated the effect of pollinators on the oil’s fatty acid composition while rapeseed is cultivated for oil. Here, we quantified the contribution of insect pollination on rapeseed production in terms of yield and oil quality in real farmers’ fields. We selected 352 rapeseeds plants into 73 fields in 3 consecutive years along a gradient of landscape to investigated effect of pollinators on yield and oil seed composition. In addition, 93 fields are followed by farmer’s survey to confirm effect of pollinators at field level. On each plant, we quantified total seed mass and oil composition on one control branch and one branch where pollinators were excluded using bags. Comparison between these two branch permit to estimate insect contribution. Abundance and richness of pollinator’s species in landscape are quantified by pan-traps. We show insect contribution to yield is to 27% and increase with pollinators richness whatever at the plant or field level. Pollinator’s richness also increases quality of the production by decreasing saturated acid in oil. This study confirms the crucial role of pollinator’s diversity in crop production.