Effects of de-inking paper sludges on soil properties and crop yields

The paper mills in Quebec produce approximately 330 000 Mg of raw de-inking paper sludges (RDS) per year. These residues are rich in cellulose and lig nin and may be used as soil conditioner. The effects of RDS on soil chemica l properties, barley (Hordeum vulgare L. 'Chapais') growth, nutrient uptake and yields, and their residual effect on a subsequent strawberry (Fragaria x ananassa Duch. 'Kent') crop were investigated on a Tilly silt loam (Gley ed Humo-Ferric Podzol) From 1994 to 1996. Four rates of RDS (0, 15, 30 and 45 Mg ha(-1)) on a wet-weight basis were combined with four rates of supple mental N-mineral fertilizer (0, 45, 90 and 135 kg ha(-1)) as NH4NO3. The so luble inorganic N content of soil sampled 30 d after treatment application was significantly lower in plots treated with 45 Mg RDS ha(-1) at all N rat es. However, soluble inorganic N concentrations increased significantly wit h RDS rate to 20-cm depth in June 1995. The RDS application increased soil water content and Mehlich-3-extractable P, K, and Ca in the first year. Bar ley yields were reduced by 50% when 45 Mg RDS ha(-1) was applied without su pplemental N-mineral fertilizer. The amount of N-mineral fertilizer needed to overcome N immobilization resulting from RDS increased with RDS rates. S trawberry yields were not significantly affected by residual RDS or N-miner al fertilizer. Changes in plant tissue metal contents were not significant. The results of this study indicate that RDS application has a positive sho rt-term effect on soil water, P and K availability but reduces plant-availa ble soil N in the growing season after spring application. The RDS may be u sed effectively as soil amendment if the crop receives adequate supplementa l N-mineral fertilizer.