Silicon application increases phosphorus uptake by rice: Dynamic rhizosphere processes

Abstract

Rice, feeding over half the global population, faces yield constraints from limited soil phosphorus (P) availability, while silicon (Si) can increase P bioavailability by competing for adsorption sites and stimulating rhizosphere phosphatase activity. This study investigated Si application effects on soil P availability, rice P uptake, and rhizosphere P dynamics. Laboratory soil cultivation trials used silicic acid gradients (0, 60, and 120 mg Si kg -1 soil) on Ferralsol, Anthrosol, Acrisol, Fluvisol, and Cambisol across six time points (0, 2, 7, 15, 30, and 45 days), followed by rice pot experiments on three selected soils (Ferralsol, Anthrosol, and Fluvisol) with two Si gradients (0 and 60 mg Si kg -1 soil). Rhizosphere phosphatase activity and available P were visualized in rhizotrons using soil zymography and diffusive gradients in thin-films techniques. Silicon application increased available P content during short-term soil cultivation, particularly in P-deficient soils. In pot experiments, compared to controls, Si application increased acid phosphatase activity by 37.5% and biomass (root + shoot dry weight) by 23.0% in Fluvisol, while increasing rice total P accumulation by 49.6% and root P:iron molar ratio by 31.0% in Anthrosol. Imaging revealed Si-induced changes in root architecture, including 12% and 11% increases in maximum vertical extension and root angle, respectively, accompanied by expanded acid phosphatase activity hotspots, thereby accelerating rhizosphere P depletion. While pot experiments showed limited Si effects on Anthrosol pH, available P, and phosphatase activity, rhizosphere imaging revealed mechanisms underlying increased rice P accumulation, demonstrating the value of high-resolution techniques for understanding rhizosphere processes. • Si application elevated soil available P content, particularly in P-deficient soils • Si increased acid phosphatase activity in Ferralsol and biomass in Fluvisol • Si increased the total P accumulation and P:Fe molar ratio in rice grown in Anthrosol • Imaging revealed Si-stimulated root architecture and P depletion in the rhizosphere

Topics & Concepts