Leaching of 15-N-Labeled Nitrate Fertilizer Applied to Barley and a Grass Ley

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Abstract
A lysimeter experiment was conducted to determine the magnitude of fertilizer-N leaching over a three-year period. Three types of lysimeters and two treatments were included, i.e., barley and a grass ley fertilized with calcium nitrate at rates of 120 and 120+80 kg N ha-1 yr-1, respectively. The N-fertilizer applied during the first year had 15-N enrichments ranging from ca. 1 to 99% atom excess (a.e.). 15-N-labeled fertilizer (ca. 99% 15-N a.e.) was also applied to three grass ley lysimeters (not fertilized with 15-N earlier) during the third year. Approximately 10% of the nitrate leached from lysimeters with barley during the first year originated from fertilizer. Dry weather during the first two years reduced N-leaching substantially. Leaching of 15-N-labeled fertilizer never exceeded 1 kg N ha-1 yr-1 from either the barley or the grass ley lysimeters. A maximum of 1.2% of the 15-N-labeled fertilizer applied to the barley was recovered in drainage water during the three years of the study. The grass ley generally had lower proportions of nitrate-N derived from fertilizer in drainage water compared with barley. The amounts of fertilizer-N appearing in drainage water were similar for each type of lysimeter and each level of 15-N enrichment.
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