Ammonium‐loaded clinoptilolite: a slow‐release nitrogen fertilizer for sweet corn

Abstract

Nitrogen (N) loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate (NO₃ ^‐) contamination in surface and ground waters and increases N applications to crops. Ammonium‐loaded clinoptilolite (A‐Cp) may reduce N leaching from sandy soils while sustaining plant productivity. We conducted two greenhouse plant growth experiments with sweet corn (Zea mays L.). Pots containing a sandy soil planted with sweet corn were fertilized with either ammonium sulfate (AS) or one of three size fractions of A‐Cp, small (<0.25 mm), medium (0.25 to 2 mm), or large (2 to 4 mm), at rates of 112, 224, or 336 kgN ha^‐1 (Experiment #1) and 112 or 224 kg N ha^‐1 (Experiment #2). We compared ammonium (NH₄ ⁺) and NO₃ ^‐ leaching from these pots and compared corn relative growth rates (RGR), leaf area ratio (LAR), and net assimilation rate (NAR) among all N fertilizers. Soil amended with AS leached 10 to 73% of the added N, depending on N rate, whereas <5% of the added N leached from the A‐Cp amended soil regardless of N rate and Cp particle size. No differences in corn growth were observed among N fertilizers, however, plants fertilized with A‐Cp assimilated significantly more N than AS fertilized plants. Results indicate fertilization with A‐Cp will minimize N leaching from sandy soils while sustaining normal corn growth.

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