| Abstrakt: |
Three experiments were conducted over a 3‐year period to compare various urea materials and ammonium nitrate as N sources for hay production on flooded meadow sites. Each experiment was a complete factorial combination of fertilizer N sources and rates broadcast once in the spring on established forage prior to flood irrigation. Experiment 1 in Gunnison County consisted of ammonium nitrate (AN), urea (U), sulfur‐coated urea (SCU), and urea ammonium polyphosphate (UAPP) broadcast at rates of 0, 67, 134, 202, and 269 kg N/ha. A second season's data was collected to evaluate carryover N. Experiments 2 and 3 were conducted in Jackson County for a single season and consisted of AN, U, UAPP, and urea ammonium sulfate (UAS) broadcast at 0, 90, 179, and 269 kg N/ha. Hay yields and N uptake were significantly increased by N fertilizer at each location; there was no significant response in hay yield or N uptake resulting from residual N in the second season of Experiment 1. Source of N did not influence hay yields nor N uptake. The N content of the hay was significantly influenced by the N fertilizer rate at two locations and the N source at one location. In general, hay yields and N uptake increased with increasing rates of fertilizer N. Fertilizer efficiency was low at all locations, ranging between 8.5 and 19.6 kg hay/kg N. Fertilizer N recovery was <30% for all treatments. Both efficiency and recovery of N tended to decrease with increasing N rates. |
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