Abstract.The effects on nitrate leaching of incorporation of paper mill waste at three cultivation depths in fields previously cropped to iceberg lettuce and calabrese are reported. In the lettuce experiment, incorporation of 40 t DM paper mill wasteiha resulted in a decrease in N leaching (measured with suction cups) from 177 to 94 kgiha (S.Ed=23). Deep ploughing with and without paper waste increased N leaching from 105 kgiha (normal ploughing or surface incorporation) to 172 kgiha (S.E.d = 27). Measurements of nitrate leaching using deep soil cores showed a less clear cut effect. Nitrous oxide (NZO) emissions were very high immediately after paper waste was ploughed in to a depth of35 cm. Non-significant increases in biomass N content were measured in the spring following paper waste application. There was no significant reduction in plant N uptake in subsequent crops. Removal of above-ground crop residues did not have a significant effect on nitrate leaching or NzO losses. In the calabrese experiment, application of 40 t DM paper mill wasteiha followed by summer cropping with iceberg lettuce caused a decrease in N leaching (measured using deep soil cores) from 227 to 152 kgiha (S.F,.d = 22, mean of all cultivation treatments).
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