Irrigation of primary treated and anaerobically treated meat-processing wastes onto pasture: Lysimeter trials

Primary treated and anaerobically treated meat-processing wastes were irrigated onto pot lysimeters containing Horotiu sandy loam (Entic Dystrandept) and a ryegrass/clover sward. Four effluent application rates were used: 0, 500, 1000 and 2000 kg N ha⁻¹ year⁻¹. For primary and anaerobically treated effluent, pasture production was maximal at 2000 kg and 1000 kg N ha⁻¹ year⁻¹, respectively. Herbage from lysimeters receiving anaerobically treated effluent contained much higher concentrations of nitrate-nitrogen than that from lysimeters receiving primary treated effluent. Health problems may result when ruminants feed on high-nitrate materials. Based on ‘safe’ nitrate levels in the herbage, the upper loading limit would be about 500 kg N ha⁻¹ year⁻¹ for anaerobically treated effluent and about 1000 kg N ha⁻¹ year⁻¹ for primary treated effluent.