| Abstrakt: |
Core lysimeters containing undisturbed coarse sandy soil (from grassland) were amended with a high rate of anaerobically digested sewage sludge (equivalent to >1,000 t ha -1). Water, at a rate equivalent to the mean weekly rainfall for the soil, was applied to amended and control lysimeters for 30 weeks and the leachate analysed for anions and cations. Lysimeters were also destructively sampled at intervals throughout the experiment and soil samples were analysed for extractable NH 4 +-N, NO 3 --N and PO 4 3--P. Ammonium N leached for about 11 weeks from the amended lysimeters, then abruptly stopped. A similar amount of NO 3 --N leached, but leaching was continuing when the experiment finished. The control lysimeters leached as much NO 3 --N as those that were amended, but no NH 4 +-N. The amended lysimeters also leached NO 2 --N. Negligible PO 4 3--P, but large amounts of SO 4 2- were leached from the amended lysimeters. Concentrations of extractable NH 4 +-N and PO 4 3--P were very high in the amended soils, but NO 3 --N concentrations remained low throughout the experiment, indicating that nitrification rates were low and/or that denitrification rates were high. [ABSTRACT FROM AUTHOR] |
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