Biomass and metal yield of co-cropped Alyssum murale and Lupinus albus

Abstract

Combining crops is a potential option to gain more value from ultramafic soils. This work was designed to investigate the co-cropping of a legume, Lupinus albus, and a Ni-hyperaccumulator, Alyssum murale Waldst. & Kit, and determine whether growth and metal uptake would be altered by a companion plant. A pot experiment was conducted in a growth chamber in two serpentine topsoils that were low in P but differed in Ni and Mn concentrations. The soils were a Magnesic Eutric Cambisol (S1) and a Hypermagnesic Hypereutric Cambisol (S2). Pots were split into two compartments along the diagonal by a double-layer nylon mesh, and the space between the meshes was filled with same soil. Each plant was either mono-cropped (sown on both compartments) or co-cropped (one species per compartment). For all combinations, two treatments were prepared: one with no P fertilisation and the other with P addition. L. albus and A. murale plants were grown for 45 and 57 days respectively. Results showed that both plants responded positively to P fertilisation. In co-cropping systems on non-P treatments, L. albus accounted for the majority of the total biomass (higher than 90%), whereas with P addition the contribution of A. murale reached almost 40%. P fertilisation provoked an increase in Ni concentration in A. murale (S1), or no change (S2). Co-cropping significantly reduced Ni concentration in shoots of A. murale and total Ni exportation was slightly lower than when plants were grown individually. L. albus accumulated high concentrations of Mn and co-cropping and P deficiency increased Mn uptake. In this co-cropping system L. albus and A. murale interacted positively, and this association is a feasible means to increase the productivity of phytomining on serpentine soils provided appropriate fertilisation is supplied.