Effects of De-inking Sludge on soil Properties and Corn Growth

Abstract

The large amount of organic carbon content present in de-inking residues makes them attractive for use in agricultural soils as an organic soil amendment. Greenhouse bioessays were undertaken to evaluate the agronomic value of de-inking sludge (DS). It was incorporated in a sandy soil to study the effects of different rates of de-inking residue amendments and N fertilizer combinations on soil properties and growth of corn. Particular attention was given to trace element concentrations. In a split factorial design, three variables were investigated: harvest time (after 20, 40, and 60 days), application rates of DS (0, 35, 70, and 105 t·ha–1), and four N rates (0, 140, 280, and 420 kg·ha–1). Chemical analyses of the fresh residues did not indicate the presence of heavy metals at levels potentially toxic to the environment. Soil chemical properties were clearly improved following the incorporation of DS. For example, adding different amounts of DS had a significant impact on the pH, the cation exchange capacity, and soil moisture. In addition, salinity was not affected with DS application. Seed germination was high in all the treatments and was not significantly influenced by DS application. Moreover, results on vegetative growth indicated a good relationship between the C:N ratio and biomass production. The DS combined with supplemental fertilizer seems to have a positive effect on plant growth. Overall, these results suggest that the limiting factor in de-inking paper sludge valorization is the amount of N available to the plant. Also, no other toxic products were found that could be harmful to the environment.