In 1991, a project was initiated in collaboration with the Daishowa paper company to characterize de-inking residues resulting from paper recycling in detail and to determine the value of this organic residue as an amendment to agricultural soils. Our objective was to determine the effects of field applications of de-inking residues on potato crop culture. In 1992, 1993, and 1994, experimental plots were established and maintained at the Horticultural Experimental Farm of Laval Univ. A factorial design was composed of four replications of four doses of de-inking residues (0, 15, 30, and 45 t·ha–1) combined with four doses of N (0, 45, 90, and 135 kg·ha–1). Treatments were applied to a total of 64 plots. The results indicate the importance of adjusting the fertilization to prevent the immobilization of N by the residues. In 1992, as a result of adding de-inking residues, potato yields were increased significantly when sufficient N fertilizer was added. However, significant decreases in yield were noted when a high level of de-inking residues was applied without any adjustment of the C:N ratio. In 1993, potato yields were reduced in treatments having a second application of residue at the highest doses (30 and 45 t·ha–1), even when additional N was provide. Interestingly, harvested tubers gave no indication of toxicity effects due to heavy metals or other contaminants. Results also will be discussed in terms of overall potato quality and the incidence of disease.
S. Côté, C.J. Beauchamp, and S. Yelle
A. Fierro, J. Norrie, A. Gosselin, and C.J. Beauchamp
Paper recycling generates large quantities of de-inking sludge, which is disposed of mainly by landfilling. More ecological disposal alternatives include land application and use as a container nursery medium. In this study, raw de-inking sludge was evaluated as a medium component supplemented with applications of four N fertilization regimes for the growth of three grass species (Festuca ovina duriuscula, Agropyron elongatum, Alopecurus pratensis), and four regimes of P fertilization for the growth of three Rhizobium-inoculated legumes (Medicago lupulina, Galega orientalis, Melillotus officinalis). Fertilizer was applied on the basis of sludge rate to maintain a uniform C: N ratio across sludge treatments. In one experiment, sand was mixed with 0, 10%, 20%, and 30% sludge by volume and 20% perlite, while in a second experiment, mineral soil was mixed with 0, 27%, 53%, and 80 % sludge and 20% perlite. Results indicate that shoot dry weight of all species increased with the amount of sludge in the mixture in tests with sand. In the soil mixture experiment, grasses showed the best response to treatments of 53% sludge mixture at the two highest N treatments. In general, shoot dry weight was more directly related to the total amount of N applied than to the C: N ratio of the substrate. The nutritional status (foliar N and P) also was investigated for one grass and one legume species.