CONICET | Buscador de Institutos y Recursos Humanos

A more comprehensive understanding of the mechanisms of phosphorus (P) efﬁciencyis agronomically signiﬁcant to advance in the design of crop management schemesthat increase P efﬁciency and reduce the need of fertilizers. Phosphorus efﬁciency isdeﬁned as the ability of a plant to acquire P from the soil and/or to utilize it in theproduction of biomass or the harvestable organ. Because most parameters related to Pefﬁciency vary according to the growth conditions and isolation of the individual effectof P efﬁciency is not straightforward; plants must be grown in uniform experimentalconditions to obtain a fair comparison of their nutrient acquisition and utilization. In thiswork, we compare the ability of soybean, sunﬂower, and maize to utilize and acquiresoil P. Field and greenhouse experiments including different P levels were conducted.The general observation was that the three species ranked differently according to thespeciﬁc parameter of P efﬁciency considered.Maize clearly showed higher P utilizationefﬁciency than soybean and sunﬂower, either expressed as biomass or as grain producedper unit of absorbed P. In turn, soybean and sunﬂower exhibited higher acquisitionefﬁciency than maize. Soybean showed the shallowest root system: 69% of the totalroot length was concentrated in the top 20 cm of the soil. Phosphorus uptake per unitroot length was rather similar among the three species, but soybean and sunﬂower hadhigher P uptake per unit of root weight. This can be explained by the higher speciﬁc rootlength (SRL) and speciﬁc root area (SRA) of both dicots. For example, SRL averaged59, 94, and 34 m g−1 in ﬁeld grown soybean, sunﬂower, and maize, respectively. Themore favorable root morphology determined that soybean and sunﬂower can exploremore soil with the same belowground biomass and absorb more P per unit of carbon invested belowground. Since the three species exhibited similar values of P uptake perunit root length, we hypothesize that the capacity of each segment of root to deplete soilP fractions is similar.