Ammonium Retention in Sand Amended with Clinoptilolite

Clinoptilolite zeolite has a rigid three‐dimensional lattice with 10 −9 m sized tunnels, and an affinity for NH + 4 on its internal exchange sites. These internal tunnels are too small for 10 −6 m size microbes to access; hence, clinoptilolite has the potential to physically protect NH + 4 from nitrification by microbes, and may reduce volatilization losses. The objective of this study was to evaluate NH + 4 retention of sand amended with clinoptilolite. Retention of NH + 4 on clinoptilolite amended sands incubated at 20% volumetric water content, was studied in the laboratory. Treatments were washed mortar sand amended with 0, 5, and 10% clinoptilolite by volume and 2.38 and 3.57 moles of NH + 4 m −3 of soil. Retention was evaluated by monitoring NH + 4 loss from the soil mix. Loss of NH + 4 decreased with increasing clinoptilolite amendment. Losses also decreased when the amount of NH + 4 initially applied was decreased. The effect of clinoptilolite in retaining NH + 4 was more pronounced when the amount of NH + 4 initially applied was increased. Clinoptilolite reduced NH + 4 losses from the soil mix and would allow increased plant N fertilizer‐use efficiency. Thus clinoptilolite‐amended sands have potential as a growth medium for turfgrasses on golf greens, where N use efficiency is typically low.