Increased uptake and accumulation of phosphorus and other nutrients by legumes enhance their bioavailability for non-legume species

Legumes are promoted in agroecosystems for their ability to fix atmospheric nitrogen (N), thereby reducing or eliminating the need for N fertilisation while also contributing N-rich organic residues, which non-legume species can subsequently utilise. In phosphorus (P)-poor soils, certain legumes appear to access less available forms of P, converting them into organic P and facilitating its use by non-legume species. This study evaluated seven legume species/cultivars and one grass species (as a control) in a trial conducted in low-fertility soils under four different growing conditions (location × year). The objective was to investigate the role of legumes in P and other nutrient uptake and accumulation in plant tissues. Some lupins and broad beans accumulated up to 30 kg/ha of P in their biomass, even without accounting for P in the roots. Calcium (Ca) and magnesium (Mg) concentrations in plant tissues were also significantly higher in legumes than in grass. In addition to concentrating certain nutrients in their tissues, legumes produced substantially more biomass due to their access to atmospheric N, resulting in considerably higher nutrient accumulation. Ca and Mg in some legumes exceeded 100 and 40 kg/ha in aboveground biomass, respectively, whereas in grasses, they remained below 4 kg/ha. Thus, when legumes are cultivated as green manure, these nutrients are returned to the soil in organic form, which can subsequently become available to non-legume crops through the mineralisation process of the organic substrate. Therefore, cultivating legumes not only enhances N availability for other species but also improves the cycling of other essential nutrients.