How biodiversity affects terrestrial productivity is permanent to the maintenance of ecosystem services under global change. One mechanism that determine the biodiversity-productivity relationship is through plant-soil feedbacks (PSF) whereby soils altered by the resident plants and this conditioning in turn affects the ability of residents to persist. Eight herbaceous plant species were planted in monocultures and mixtures with three species diversity levels in field. Three conditioned soils conditioning by a single species  and multiple species were used in pots for subsequent responding phase. We found a ‘conditioning and responding’ matching between plant diversity and conditioned soil diversity. PSF promoted greater plant productivity in mixed-conditioned compared to mono-conditioned soil. Also, the positive relationship between biodiversity and productivity was strongly maintained in mixed-conditioned soil rather than in mono-conditioned soil. And such effect gradually plateaued at higher levels of prior plant diversity corresponding to soil microbial diversity. The biodiversity-productivity relationships are importantly co-determined by a soil-derived legacy effect of plant diversity, highlighting that a soil conditioning stage is required for exhibiting biodiversity-productivity relations to arise. This finding is particularly pertinent to agroecosystem managements when a transition is made from monoculture to intercropping/rotations, and partly explaining why yield increment takes time to accrue.