Phosphorus acquisition by faba bean, blue lupin, and chickpea in relation to soil phosphorus status

The efficiency of soil phosphorus (P) mobilization and uptake by plants depends on a complex combination of factors, including plant P acquisition strategies and soil P availability. The objective of this study was to assess and compare the capabilities of three legume species (blue lupin (Lupinus angustifolius L.), faba bean (Vicia faba L.), and chickpea (Cicer arietinum L.)), which may be used as green manures in temperate crop systems to acquire P from a soil with different levels of plant‐available P. Three cycles of each legume were grown in a glasshouse over a 6 month period in the same soil type with high (Olsen P: 47 mg kg−1) and low (Olsen P: 9 mg kg−1) levels of plant‐available P. Measurements included above—and below—ground plant biomass and P uptake, in addition to determination of acid and alkaline phosphomonoesterase activities, microbial P, and P fractions in soil at the end of the experiment. In both soils, plant biomass, P uptake, and microbial P were all higher under faba bean compared to blue lupin and chickpea (p < .05). In the low‐P soil, faba bean increased alkaline phosphomonoesterase activity (p < .05). Significant depletion of inorganic P in the soluble (46%–69%), labile (29%–42%), and moderately labile (15%–16%) pools and increase of organic P in the labile (13%–18%) and total (7%–13%) pools occurred under faba bean compared with blue lupin, while changes under chickpea were between those determined for faba bean and blue lupin (p < .05). The findings of this study indicated that inclusion of faba bean green manure may have the potential to improve overall P use efficiency by enhancing mobilization of labile soil inorganic P, although further research is required to investigate mobilization of more stable forms of soil legacy P and quantify the potential of faba bean as a green manure crop under field conditions.