Manganese-Exchanged Smectite Clays as a Potential Controlled-Release Fertilizer for Mn Nutrition: Comparative Evaluation of Mn-Laponite and Mn-Montmorillonite

and MnEDTA. All treatments rapidly corrected Mn deficiency. At 8 weeks, biomass under Mn-laponite2, Mn-montmorillonite, and conventional fertilizers was comparable to or higher than that of the deficient control. Mn-laponites provided rapid Mn availability, whereas Mn-montmorillonite exhibited slower, sustained release. Smectite type thus controls Mn-release dynamics, supporting the use of synthetic clays as fertilizers in calcareous systems, though field validation is still pending.