AMMONIUM-LOADED CLINOPTILOLITE - A SLOW-RELEASE NITROGEN-FERTILIZER FOR SWEET CORN

Nitrogen(N) loss from irrigated cropland, particularly sandy soils, si gnificantly 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 sus taining plant productivity. We conducted Mo greenhouse plant growth ex periments 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 kg N 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 compar ed corn relative growth rates (RGR), leaf area ratio (LAR), and net as similation rate (NAR) among all N fertilizers. Soil amended with AS le ached 10 to 73% of the added N, depending on N rate, whereas <5% of th e 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 signific antly more N than AS fertilized plants. Results indicate fertilization with A-Cp will minimize N leaching from sandy soils while sustaining normal corn growth.