Crop management modifies the benefits of insect pollination in oliseed rape

In a factorial field plot experiment, high and low levels of inorganic nitrogen and of insect pollinators visiting the crop were manipulated and their combined effects on oilseed rape yield were quantified. A third factor was also included, testing whether different cultivars responded differently to the tested factors. Insect pollination was required to reach high yield and seed quality (oil content). Final benefits of pollination service were, however, greatly modified by cultivar, where the seed yield of the open-pollinated cultivar largely depended on insect pollination whereas the two hybrid cultivars did not. A near significant interaction between nitrogen input and insect pollination was also found, i.e. benefits to crop yield from insect pollination seemed to increase with decreased nitrogen levels. The differential response of the three cultivars suggested opportunities to use cultivars that are less dependent on insect pollination in landscapes where this service has been deteriorated. Increased access of nitrogen seems to partly compensate yield losses from poor insect pollination. Integrating conservation, environmental and agronomic sciences is therefore crucial to sustain agriculture productions through optimized management of agronomic inputs and biodiversity-based ecosystem services.