Speaker
Description
Phosphorus (P) is an essential macro-nutrient that often limits plant productivity in alkaline-calcareous soils, because sorption and precipitation reactions are strongly favored in these typical soils. Hence, the importance of understanding the root-soil interface, known as rhizosphere, especially the processes and mechanisms involved in plant P utilization. A greenhouse experiment was conducted to investigate four P sources (Rock phosphate (RP), Orthophosphate (OrthoP), Polyphosphate (PolyP), and Triple superphosphate (TSP) compared to the control (zero P application) on: root morphological traits, plant growth parameters, shoots and roots P uptake, and root exudates, using white lupin (Lupinus albus) as indicator crop. Rhizosphere and bulk soils were collected and analyzed for pH, bioavailable P, and enzyme activities (acid and alkaline phosphatases). Our results showed a significant difference between the effects of different P sources on dry weights of shoots and roots, and root-to-shoot ratio. Acid phosphatase activity increased significantly in the rhizosphere soil compared to the bulk soil regardless of the P source with the highest activity (p < 0.05) observed under RP. However, no significant effect was found in the activity of alkaline phosphatase between the rhizosphere and bulk soils, except for RP and PolyP. Moreover, rhizosphere soil pH decreased significantly compared to the bulk soil pH, especially in the RP-treated and the control soils. We conclude that rhizosphere processes involved in plant P mobilization and acquisition are P source dependent.
Keywords: phosphorus source, root exudates, white lupin, alkaline soil, calcareous soil, phosphatase
