Decreasing nitrogen leaching from sandy soil with ammonium-loaded clinoptilolite

Nitrogen (N) loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate (NO3-) levels in surface and groundwaters, In this study, as a preface to a plant growth study, we compared N leaching from NH4+-loaded clinoptitolite (A-Cp) and (NH4)(2)SO4 (AS) in two media: a rounded quartz sand and a sandy soil. We hypothesized that quartz sand or soil amended with A-Cp would leach significantly less N than these media amended with AS, and that more N would leach from smaller A-CD size fractions than front larger A-Cp size fractions. Ammonium sulfate, or one of the three A-CI, size fractions, small (<0.25 mm), medium (0.25-2 mm), or large (2-4 mm), was banded at a depth of 5 cm in leaching columns filled with inert quartz sand at a rate of 112, 224, or 336 kg N ha(-1). The experiment was repeated with sandy soil in greenhouse pots at rates of 112 and 224 kg N ha(-1). The columns and Dots were leached for about 40 d with a simulated irrigation water. Significantly more N, as NH4+ and NO3-, leached from AS amendments than any of the A-Cp amendments in both experiments. Results indicated that the larger the A-Cp size fraction, the slower NH4+ is released from A-Cp. Ammonium-Cp slowly releases N and could significantly minimize N leaching from sandy soils compared to AS.