Effect of Hydrochar from Anaerobically Digested Sewage Sludge and Manure as a Soil Amendment on Soil Properties and Plant Responses

Soil amendments, such as pyrochar (PC) and hydrochar (HC), have the potential to enhance soil properties and crop yields. The objective was to investigate the effects of HC from anaerobic digestion effluent (ADE) of sewage sludge (SS), ADE of manure (M), and PC, as soil amendments. Lettuce seeds were sown and grown in soil amended with chars at rates of 1 to 15 g char/kg soil. Soil properties and plant responses were compared to soil without amendment (control). Soil amended with HC-ADE-SS and HC-ADE-M had higher pH, phosphorus content, and cation exchange capacity than the control. All treatments and the control resulted in 80% + emergence rates. Root dry mass of plants grown on soil with 10 and 15 g/kg was higher than the control. No negative effects were observed in emergence and whole-plant dry biomass, indicating that HC-ADE-SS and HC-ADE-M could be amended without negative impacts on soil properties and plant responses.