Corn phytoliths: properties and potential for silicon recycling

Abstract

Corn absorbs silicon (Si) from the soil and stores it as phytoliths in its tissues. When corn residues (leaves and stalks) are recycled, these phytoliths serve as a vital and renewable Si source for subsequent cropping seasons. However, the dissolution behavior of corn-derived phytoliths remains poorly understood. This study investigates phytolith presence in soil-corn systems in Northern Vietnam, a region susceptible to intense leaching and Si loss. Corn residues were converted into phytolith-rich biochar and ash, and their dissolution properties were evaluated using batch experiments and scanning electron microscopy. In these batch experiments, the role of microorganisms, specifically Bacillus velezensis, in facilitating dissolution was also examined. Results indicate that corn accumulates Si primarily in its leaves (2.98 to 35.8 mg g⁻¹), where condensed Si forms distinct structures such as thorn-like and bilobate phytoliths. The extent of phytolith dissolution, and thus Si release, depended on the corn leaf treatment. Over 14 days, Si release rates followed the order: ash (37.5 mg g⁻¹) > biochar (11.6 mg g⁻¹) > leaf powder with Bacillus velezensis (5.32 mg g⁻¹) > leaf powder under sterile conditions (1.77 mg g⁻¹). Among these approaches, producing phytolith-rich biochar under anaerobic conditions appears most effective, as it ensures prolonged Si availability while simultaneously contributing substantially to carbon sequestration. For situations requiring rapid and large-scale Si replenishment, direct combustion of corn residues, facilitated by microbial support, presents a suitable approach.