Acidification of lime-stabilized biosolids in formulation of synthetic topsoil

Uses of lime-stabilized biosolids in container media or topsoil formulations may be limited by alkalinity imparted by lime added for reductions in vector attraction and pathogens and for suppression of odors. This experiment was conducted to assess the suitability of quicklime-stabilized biosolids mixed with calcareous or noncalcareous sand and with sulfur or aluminum sulfate as acidifying agents for development of synthetic topsoil for turfgrass (Lolium perenne L.) production. Grass emergence and growth were inhibited in media that were not amended with an acidifying agent. Additions of aluminum sulfate were more effective in acidification than sulfur, causing an immediate drop in pH, whereas additions of sulfur required about 2 months for a depression in media pH. With time, electrical conductivities were higher in media with additions of sulfur than in media with additions of aluminum sulfate. Calcareous sand mixed with biosolids (2 sand:1 biosolid, v:v) gave a better medium for growth of turfgrass than noncalcareous sand mixed with biosolids. Calcareous sand flocculated biosolids, whereas noncalcareous sand dispersed them. Results suggest that calcareous sand and aluminum sulfate are effective agents for diluting and acidifying biosolids for development of a suitable topsoil medium for turfgrass production.