N-fixing legume and sustainable P management
Romans used to grow lupins (Lupinus spp.) as a green manuring crop for improving soils (Burtt, 1981). Lupins are N-fixing legumes that are reported to fix 300-400 kg N/ha, in Europe and Australia (Jansen, 2006). Lupins are beneficial to the next crop. Organic rye yielded 0.5 t/ha more when preceded by yellow lupin than when preceded by spring beans (PGRO, 2014).
Lupins are valuable legumes for sustainable P management: in soils depleted in available P, lupins form specialized cluster root structures and/or release P-mobilizing carboxylates that free it from insoluble forms (Lambers et al., 2012).
Soil improver and phytoremediation
Thanks to its deep taproot, the lupin plant improves soil texture and drainage. Lupins can be used for phytoremediation. Lupins may extend the phytoremediation period and increase the bioavailability of metals in polluted soils under recovery (Fumagalli et al., 2014). In mixed cultures of bioenergy crops, lupins (Lupinus albus and Lupinus angustifolius) have the ability to mobilize trace elements during and make these elements available for co-cultured species. Lupines mobilize trace elements by carboxylates and enzymes exudation and by lowering the pH value in the rhizosphere. In a comparison between white and blue lupin for trace element mobilization, white lupin was more effective than blue lupin and thus recommended for phytoremediation (Hentschel et al., 2016).