We investigated whether losses in biomass yield under drought are related to species’ nitrogen (N) acquisition and drought-induced N deiciency. In a three-factorial experiment, monocultures of four species that difered in their functional trait regarding N acquisition were established in a ield experiment (irst factor). Species were the non-legumes Lolium perenne L. and Cichorium intybus L. (no N2 ixation), and the legumes Trifolium repens L. and Trifolium pratense L. (N2 ixation). A summer drought was simulated with complete rain exclusion for ive weeks, and drought efects were compared to rainfed control conditions (second factor). In addition, application of mineral N fertiliser was manipulated so that plots received no N during drought or 60 kg N ha-1 (third factor). Under drought, plant-available soil N was strongly reduced (P<0.001, compared to the rainfed control). Legumes were consistently less N-limited than non-legumes (P<0.001) and, at the end of the drought period, N derived from the atmosphere in the legume T. repens was 72%. Legumes’ biomass yield was less afected by drought (-19%) than non-legumes’ yield (-38%). Moreover, N fertilisation mitigated the drought efect on yield of non-legumes from -38% (no N) to -22% (60 kg N ha-1). In conclusion, this improved yield-resistance to drought was related to mitigation of drought-induced N limitation through symbiotic N2 ixation (legumes) or N fertilisation (non-legumes). hus, cropping legumes could improve yield resistance against drought events as projected under climate change.
