Regeneration of Soluble Boron by Reclaimed High Boron Soils

The ability of reclaimed high boron (B) soils to reestablish elevated soil solution B concentrations has been termed boron regeneration . Three natively high B soils and three B‐amended soils were “reclaimed” in laboratory columns using four leaching strategies. The reclaimed soils were stored for 30 d and releached. Effluent B concentrations increased in all soils during storage, producing potentially phytotoxic concentrations in some cases. Regeneration was enhanced by increasing the solution driving force during initial leaching or by high post‐reclamation moisture content. Regenerated B concentrations were inversely related to the quantity of water used for reclamation. Each unreclaimed soil appeared to contain a finite amount of reclaimable B. The soil regenerative ability diminished with depletion of the reclaimable B component. Periodic leaching controlled the redevelopment of excessive B concentrations, eventually leading to permanent reclamation. The six soils fell into two behavioral groups when fitted to an empirical B reclamation model. The recently boronated soils were more efficiently reclaimed than those containing native B. The model reasonably approximated the initial leaching data of the natively high B soils; however, regeneration of soluble B caused the experimental data to deviate from the model prediction. Allowing soluble B to regenerate between leaching water applications may enhance leaching efficiency and reduce reclamation water requirements.