Abstract

The aim of this study was to evaluate the effect of pretreatment on the phytotoxicity and leaching of nitrogen and phosphorus in biosolids from anaerobic digestion in silty loam soil. Soil columns filled with silty loam soil and biosolids (BS) stabilized by conventional (CAD) and advanced (AAD) anaerobic digestion were installed. AAD consisted of the application of sequential pretreatments: ultrasound followed by a low thermal process. The BS loads were equivalent to 30 ton/ha (CAD30 and AAD30) and 90 ton/ha (CAD90 and AAD90), and the soil columns were watered with 29 mL/day of distilled water. Phytotoxicity was evaluated by germination and root growth inhibition and by the germination index (GI) of Triticum aestivum, Lactuca sativa, and Raphanus sativus seeds. Nitrogen leaching varied from 0 to 9 mg/week, while phosphate leaching did not exceed 0.01 mg/week. The nutrient leaching rate depended on the BS application rate and not on the use of pretreatment (p<0.05). Regarding phytotoxicity, BS application presented a tendency to attenuate the inhibition caused by the silty loam soil, with GI values ranging from 31 to 50%, 62 to 63%, and 70 to 82% for L. sativa, R. sativus, and T. aestivum, respectively.