Adeline Becquer1, 2, Rebecca E. Haling1, Adam Stefanski1, Alan E. Richardson1, Richard J. Simpson1
1 CSIRO Agriculture and Food, GPO Box 1700, Acton, ACT, 2601. Richard.firstname.lastname@example.org
2 INRA, UMR Eco&Sols, 2 place Viala, 34060 Montpellier, Cedex 1, France
Two pot experiments were conducted to assess whether growth of subterranean clover (Trifolium subterranean) increases when it was grown together with white lupin (Lupinus albus), a legume that can access fixed-phosphorus (P) in soil by secreting of organic acids from its roots. Total shoot dry mass of microswards of clover interplanted with lupin was significantly higher in P-deficient soil, compared to clover monocultures. The benefit to P-efficiency was greater when there was more lupin growing in the mixture. However, the clover component of the sward was depressed by the lupin. In a second experiment, subterranean clover and white lupin were interplanted with their shoots physically separated to assess whether mobilisation of P by the lupin directly improved the P nutrition of the interplanted clover. However, the shoot dry matter and P uptake by subterranean clover were generally lower when grown in interplanted treatments, compared with growth and P uptake in clover monocultures. This suggested that interplanted lupins had not “facilitated” improved P acquisition by the clover; instead the improved yield of mixed swards in low-P soil was more likely the result of “complementarity” or “niche differentiation”, with the companion species exploring different soil horizons and/or different soil P resources.