Phytotoxicity of pulp industry sludge in Festuca arundinacea and Triticum aestivum in different soils

ABSTRACT The use of alternative waste products as organic soil amendments has become increasingly important for researchers and the industrial sector, as they promote environmental protection and sustainable development. The objective of this study was to assess phytotoxicity of different pulp industry sludge rates applied to two soils as soil amendment, based on their effects on seed germination and radicle elongation of tall fescue (Festuca arundinacea) and common wheat (Triticum aestivum). The pulp industry sludge rates applied were 1.31, 1.57, 2.61, 3.27, 3.92, and 5.23 Mg ha-1, based on soil liming requirements. Absorbent paper and soil without sludge application were used as control treatments. The bioassay was conducted by sowing 20 seeds in 15 g of soil, which were maintained in a germination chamber at 25 °C for 7 days (T. aestivum) and 14 days (F. arundinacea) with a 12-hour photoperiod. Relative germination percentage, relative root growth, germination index, normalized residual germination, and normalized residual root elongation were evaluated. The results highlight the potential of using pulp industry sludge as an organic soil amendment, as it showed significant improvements in germination and root elongation for F. arundinacea. Although phytotoxicity was observed in T. aestivum seeds at lower sludge rates, the toxic effect decreased at higher rates, indicating that the use of pulp industry sludge is promising for agricultural and environmental applications.